1. Jovi says:
   September 19, 2011 at 7:57 pm

   
   

   Hi,
   I’m remodeling some areas in my home which call for changing some exhaust pipes on my 1984 Heil furnace. I came across one large rounded shape pipe that is doubled inside. What is the reason for doubling the pipe. I need to change the shape (from circular to rectangular due to room contraints) should I double the new exhaust pipe as well?

   Thanks-
   
   

   • Dariusz Rudnicki says:
     September 23, 2011 at 4:39 pm

     
     

     Hi Jovi,
     Double wall vent pipes are required for safety reasons and you’d have replace the existing round pipe with the same double wall rectangular (or rather oval) pipe. It’s not permitted to use single wall vent pipe in any concealed (walls, ceilings, etc.) and unconditioned areas (attic, crawlspace, garage, etc).
     
     
2. George says:
   August 16, 2011 at 4:37 pm

   
   

   When it rains in a gas water heater vent pipe where does the water go? Can the vent get stopped up and cause the pipe
   to leak inside the house?

   Where does the water go when it rains in a gas hotwater vent pipe. Can this vent get clogged up with whatever.
   
   

   • Dariusz Rudnicki says:
     August 16, 2011 at 5:53 pm

     
     

     Hi George,
     The code requires natural draft water heater vent terminations (I’m assuming this is a draft hood equipped WH) to be equipped with a listed (industry approved) rain cap. Also, most rain caps are build in such way that prevents debris or birds from falling into the vent pipe. If the rain cap (older designs) has no screen or its design does not protect from the vent pipe’s contamination, protective metal screen can be installed (check with local code enforcement division for screen size). Without the cap and screen it can get clogged, most likely by a bird or larger rodent if one can get there somehow. Birds sometimes fall into some unprotected chimneys during the cold season.

     What will happen with water that penetrates water heater’s vent pipe not equipped with a rain cap depends on the vent pipe’s shape (offsets or straight run), water heater’s state at the time of rain (burner running or not). The water might partially or completely evaporate on the interior walls of the WH vent pipe, especially it the WH’s burner is running. It may also run to the base of the water heater, onto the burner, sometimes leak through the vent pipe joints, etc. If the vent pipe connects to the larger, unprotected at the top chimney, rain water often ends up at the chimney’s base, leaking.
     
     
3. Kathy says:
   August 8, 2011 at 9:52 pm

   
   

   I noticed that the mechanical venting device on top of my water heater has gotten a little noisy when it operates. Also, there is some reddish brown ooze coming out of a joint in the exhaust pipe just above the water heater. The exhaust pipe exits out the back wall of the house, and I have wondered if an animal could get inside the pipe. My women’s intuition leads me to think that something is just not right. Do you think there is cause for concern?
   
   

   • Dariusz Rudnicki says:
     August 8, 2011 at 10:27 pm

     
     

     Hi Kathy,
     Many of those water heater power vent motors generate more noise as they get older, some of them are very noisy from the beginning. If the noise level increase is noticeable it would be wise to check the motor / blower assembly. It might be the motor or / and the blower blades. The whole assembly sometimes becomes loose (because of the constant vibration) and it might just require re-tightening. In some cases it’s the blower blades touching the enclosure which creates some unusual noises. Touch the motor blower assembly (be very careful not to get burned) a few minutes after it starts operating. If it is very hot you should have a professional look at it.

     As for the reddish-brown ooze, regular power vented water heaters (not condensing type) should not produce any moisture. It might be some rain water that traveled inside the PVC vent pipe and caused corrosion of the motor assembly components… Right above the water heater means at the first joint, where the PVC vent pipe connects to the blower assembly?

     Water heater’s PVC vent pipe termination end should have a rodent screen installed. Without it, a bird or any small rodent capable of reaching the pipe can enter it. Check this article for more information about WH power venting – http://www.checkthishouse.com/2991/water-heater-pvc-vent-pipe-and-power-venting.html. Unfortunately I can’t see & “touch” your problem so you may need to call a plumber for detailed evaluation. Let me know if there’s anything else. Thanks
     
     

     • Kathy says:
       August 9, 2011 at 3:32 pm

       
       

       Thanks for the quick response! I think I will call a plumber, especially because you said the ooze is not normal. Plus, I’m pretty sure there is no screen on the pipe termination. I read other articles on your website, and apparently the noise issue is pretty common with power vent motors, but maybe a tightening will help. You have been very helpful, thank you.
       
       

       • Dariusz Rudnicki says:
         August 9, 2011 at 3:38 pm

         
         

         You are welcome Kathy.
         
         
4. gerald says:
   July 27, 2011 at 6:19 am

   
   

   We are looking to rent a house. while we were looking at the house the owners pointed out that they have just had a new central airconditioning installed in the house. I noticed that they had a natural flow gas furnace in the same room as the return air vent for the air conditioner. my concern is this: Will the return cause a vacume in the fluepipe and suck the exaust gases into the house instead of letting the flow naturally out the pipe? ifso how can this problem be fixed?
   
   

   • Dariusz Rudnicki says:
     July 27, 2011 at 2:39 pm

     
     

     Hi Gerald,
     Go over this article – http://www.checkthishouse.com/14/air-return-in-forced-air-heating-ac-systems.html and if that doesn’t answer your questions please let me know. If this room that contains the furnace (or any other gas burning appliances) is large enough or properly ventilated to provide sufficient amount of combustion air (http://www.checkthishouse.com/3518/chicago-condo-inspection-combustion-air-requirements.html – it applies to all places, not only the Chicago condo) for the burning process and if the return is not less than 10′ from the combustion chamber, everything should be fine. I’m assuming that this AC system is using the same air ducts as the heating system. If it’s less than 10′ between the combustion chamber – return, and / or there’s not enough combustion air in this room you’d need to hire an HVAC professional. It’s difficult for me to give you some kind of a solution because I can’t see this area, furnace installation, and I don’t have its technical data. You’d have to provide a few pictures and a lot of details that would be critical in answering it. Start from reading those two articles, maybe they will provide enough help. Let me know.
     
     
5. Caroline says:
   July 26, 2011 at 2:31 pm

   
   

   I just had a plumber come fix the exhaust pipes on my gas water heater (they were put in incorrectly.) Now the pipe isn’t completely sealed off from the exterior wall. How do I seal this?
   
   

   • Dariusz Rudnicki says:
     July 26, 2011 at 7:06 pm

     
     

     Hi Caroline,
     I’m not sure that I understand… could you describe this installation, water heater(s) location, vent pipe installation; where does it go from the top of the water heater, what type of the pipe is it (single or double wall metal, PVC). If you could add a picture of this installation it would be even better. I can’t see what you’re seeing…
     
     
6. Laura says:
   July 11, 2011 at 6:47 am

   
   

   Question – Should a gas water heater be in the kitchen next to a gas stove? There is a pipe ( i am assuming this is the vent) that is coming out of the top of the water heater that is going directly into the wall. This is a two story apartment complex with four units. I was told by the realtor that it is safe but I cannot find any information. I have never seen anything like this before. I have never used gas, my utilities were always electric. Any advice or comments would be appreciated. Thank you.
   
   

   • Dariusz Rudnicki says:
     July 11, 2011 at 10:26 pm

     
     

     Hi Laura,
     Kitchen installations of a water heater are not prohibited by code. For as long as this water heater is properly installed (gas supply, venting, water connections, TPR valve, support / strapping if required in your area) and it has sufficient amount of combustion air provided. Everything has been explained in my articles under the Plumbing / Gas Water Heater category. If you could take a few pictures of this installation (from a distance and close-ups of gas pipes, vent pipe, water pipes) and provide me with a BTU rating (on the manufacturers label attached to the WH) I should be able to tell you if everything has been correctly installed.
     Let me know, thanks.
     
     

     • Laura says:
       July 13, 2011 at 1:50 pm

       
       

       Hi, thanks for you answer. the apt i am looking at is in another state i am not sure if I can answer your questions. I was veiwing it online. I could as the agency the questions and get back to you. thanks again .
       
       
7. Sondra Smith says:
   July 5, 2011 at 4:30 pm

   
   

   We are about to replace a leaking water heater. I’ve called several places for estimates. When I called Home Depot I was told I could not use a GE 40 gallon tall water heater. We’re replacing a 21 year old Rheem Fury that’s 56 3/8 inches tall and the GE is 59 3/4 inches tall. She ask me to measure the vent height from the top of the tank to the bend of the vent. I measured about 11 inches. She said it would be too tall and suggested I get a short tank. They don’t have a short tank with a twelve year warranty we wanted to get. After talking to her. I went and remeasured. I also did some additional measurements. There are two vent sections between the draft hood before the bend totaling 6 inches. After the bend it angles up to the vent going out the chimney. This had been replaced when we bought a new furnace in 2003. They had to put in double wall venting up the stack due to regulations. From the bend to the vent from the furnace there is a 2 inch elevation. I haven’t call them back or anyone else because I think I should have someone come out first and look at it. In your opinion should 3 1/2 inches make that much difference for the water heater I want to get. I think taking out one of the vertical sections should take care of the differences in height. Thank you for you help.
   
   

   • Dariusz Rudnicki says:
     July 6, 2011 at 11:28 pm

     
     

     Hi Sondra,
     Water heater venting should be performed by following fuel gas codes and manufacturer’s requirements, which is probably what the information provided by the Home Depot was. There are vent connector tables in the fuel gas code that are used to calculate proper lengths of vent pipes above the water heater’s draft hood and they start with a 12″ vent rise. This first 12″ of a straight vent pipe above the draft hood is recommended (not a code requirement) as a minimum for the water heater to operate (discharge exhaust gases) properly.

     If there are no chimney draft problems, the chimney has been properly configured, and the water heater is getting proper amounts of combustion air… I don’t think that 3.5″ will matter. However, that 3.5″ might become a problem if you get Carbon Monoxide poisoning and try to blame it on the WH’s manufacturer.
     
     
8. jody says:
   July 3, 2011 at 1:29 pm

   
   

   Hi. I am planning on replacing my old gas water heater with a 40 gal tank. The water heater is in my bathroom (12.5′x7.5′) on an outside wall and sits on a concrete slab foundation. Can I vent it out the side without a power vent?
   
   

   • Dariusz Rudnicki says:
     July 3, 2011 at 2:08 pm

     
     

     Hello Jody,
     If it is a natural vent type water heater you can not vent it through the side wall, it has to vent above the roof. Other issue is the bathroom installation which isn’t permitted as well, unless the water heater closet is sealed from the bathroom area (air tight doors) and it has a separate, fresh air supply from exterior or other areas of the house that can be used for this purpose. Let me know if you have any other questions.
     Thanks.
     
     
9. Matt says:
   June 30, 2011 at 10:46 am

   
   

   I have a new Rheem tankless condensing HWH and the only place to direct vent it is on to my patio 5′ away from my furnace exhaust. To avoid another PVC exhaust stack in a commonly used area I would much prefer to run the intake and exhaust (separate 3″ PVC vents) up my chimney (30′ or so rise) in the existing, unlined 12″ chimney (previously used for an older furnace + HWH and now only used for soon-to-be-gone leaking HWH). How should I terminate the 2 PVC vents atop the chimney?
   
   

   • Dariusz Rudnicki says:
     June 30, 2011 at 12:25 pm

     
     

     Hello Matt,

     Go to this page: http://www.rheem.com/product.aspx?id=A1A75AAC-68F0-4C00-A8D3-37468E6D242A and open the “Use and Care Manual” pdf file (last one on the list). Pages 44, 45, 46 show the details of the direct vent, condensing type through the roof vent installation. The easiest way would be to put a metal cap on the top of the chimney opening with one or two holes in it (depending on which installation you’re going to pick). Run double wall pipe or two single wall pipes through the holes, install proper flashing, and termination connectors just like on the Rheem manual pages. Make sure that you follow all of the directions in their manual, it’s critical for the appliance to operate safely and efficiently.
     
     

     • Matt says:
       June 30, 2011 at 3:10 pm

       
       

       Thank you for the quick response Dariuz,

       Any tips on supporting the pipes vertically inside the chimney (the manual states vertical supports every 4′). Also, does the intake still have to be 12″ above the chimney level? There are two other chimney ports for fireplaces, how can I direct the intake away from exhaust from the other ports (1 unused but functional wood fireplace in the middle and 1 seldom used natural gas fireplace on the other side)? The top of the chimney is at least 36″ above the peak of the roof line.
       
       

       • Dariusz Rudnicki says:
         June 30, 2011 at 5:34 pm

         
         

         You’re welcome Matt,
         For the supports you can use plumbing pipe support clamps with horizontal rods attached to it and anchored to the chimney side walls. Unfortunately you’d have to make a few holes in the chimney along its length in order to install those rods. However, the biggest problem that I can see is the proximity of the other two chimney flues. If you run the fireplace and the water heater at the same time, your appliance might start recirculating exhaust fumes from the fireplace. To avoid any frustration in the future I’d call Rheem and explain this particular situation. According to the table on page 44 of the manual you can go 24″ above the roof (top of the chimney crown level) without any additional support. You could extend pipes further away from the fireplace flue and install some kind of a support, but the safest way would be to get that distance information from Rheem first.
         
         
10. Cindy Libolt says:
    June 23, 2011 at 11:26 pm

    
    

    We are planning on re-roofing our house this summer and the chimney which our water heater is vented is rusting out and needs replaced. The water heater is vented through the old chimney for a fuel oil furnace which has been replaced with a high efficiency furnace and no longer uses that chimney. The chimney looks to be 12″ double wall. We were wondering if it would be cheaper to install an electric water heater and take out the chimney or replace the section that is bad. The 4′ section that is rusting out is from the roof line up. Our water heater is in the basement and we didn’t know if there is any other way to vent it. The water heater is 14 yrs. old.
    
    

    • Dariusz Rudnicki says:
      June 24, 2011 at 3:29 pm

      
      

      Hi Cindy
      Is your chimney 12″ in diameter with 4″ liner inside?

      Since you have an older water heater I would suggest to consider replacing it. It might run for a few more years or it might start leaking tomorrow. 14 year water heaters are unpredictable. While replacing it you have 4 choices.

      1. new electric water heater / remove old chimney / you have to run 220V power line to the water heater’s location.
      2. new power vented water heater / eliminate the existing chimney / WH vents through the side wall of the house using PVC pipe / you’ll need one electrical outlet to power the vent
      3. new natural draft water heater (this is probably something you have now) / correct any problems with the chimney / replace corroded, deteriorated sections.
      4. new tankless water heater / eliminate the chimney / vent through the side wall of the house / you might need larger size gas line for it / the most expensive WH, probably around $2000 installed

      Get some estimates for each option. Number #4 is the most efficient type but it usually takes about 10 years to get your invested money back.

      Let me know if there’s anything else I can help you with.
      
      
11. Steven says:
    June 19, 2011 at 3:07 am

    
    

    Hi. Last year my old water heater went out, and I bought a brand new one from Home Depot. Rheem. Gas Residential – Low NOx Emissions. 40 Gallons. I installed it myself. The WH is inside a laundry room (17′x4′) on the back of a detached garage, and it sits on a concrete slab foundation. The single-wall vent (about 4′) sits on top of the draft hood, and it’s vented straight up thru the roof with a cap. Recently I noticed a problem which never happened before, and I’ve had this home for 7 years. When I turn on the hot water for about 45 seconds, I saw a small explosion (size of draft hood) from the WH by the draft hood. This is about the same time when I heard the burner came on. Then everything seemed ok. Once the burner stopped burning and someone turned on the hot water, the small explosion by the draft hood would happen again. What’s wrong? There is more than 12″ clearance in front and on the right side of the WH. Immediately to the left of the WH is the washer then the dryer to the far left. Please help.
    
    

    • Steven says:
      June 19, 2011 at 3:42 am

      
      

      CORRECTIONS: The vent pipe is a 3″ Type-B double wall, and it’s 5′ straight up thru the roof with a cap. This is a dedicated vent pipe for the WH only. The dryer has its own dedicated vent pipe to the side of the bldg.

      CLARIFICATION: The laundry room and the garage is only connected by an exterior wall, and there is no doorway between the two separated spaces.
      
      

      • Dariusz Rudnicki says:
        June 19, 2011 at 2:33 pm

        
        

        Hi Steven,
        From your description it appears that your water heater might be experiencing something similar to a puff-back. It’s a condition caused by delayed ignition of gas in a combustion chamber. The gas should ignite immediately after it’s released from the burner. If / when this is delayed, the WH’s igniter timing is off, there’s too much gas accumulated inside the burner chamber and when it finally ignites it creates that small explosion. It’s a newer water heater with a sealed combustion chamber and for that reason you can see or hear it at the draft hood area.
        One thing I can’t explain is the explosion at the end of the cycle. It might be the gas valve which is malfunctioning resulting in an erratic opening and closing.
        Another possible complication could be the amount of combustion air in this utility room. You didn’t mention how tall the room is and if it has any constantly open ventilation ports, but assuming 17’x4’x8’ ceiling you’d need 3 times as much of air to support complete (safe) combustion process of the water heater (based on 30000 BTU’s which should be stated on the label attached to the water heater / more BTU’s requires more air).
        Because of a sealed combustion I wouldn’t try any repairs by yourself. The appliance is still under warranty and you should call for the service ASAP. Let me know if you have any other questions.
        Thanks
        
        

        • Steven says:
          June 20, 2011 at 12:46 am

          
          

          Thanks for the quick reply!!! Just to clarify my comments earlier regarding the “explosion at the end of the cycle.” That doesn’t happen. What I meant to say was after the the first “explosion” and when the user has finished using the hot water, the WH will bring temp back to its normal temp AND the burner will stop burning. UNTIL the next user turn on the hot water AGAIN, the cycle repeats like clockwork. There IS NO second explosion at the end of a cycle.

          The laundry room is 17′ x 4′. The height on the front 17′ wide (where the entry door is) is 6′, and the height on the back (where it shares the same wall as the garage) is 7′. So as you enter the laundry room, the roof slopes upward toward the back wall. On top of both (front and back) walls are openings between 2x4s at about 24″ on center. T’here are plenty of air flow betweeen the outside air and inside the front wall, and there are plenty of air flow between inside the back wall and inside the garage. Along the front wall, there is 8″ x 16″ vent. Along one of the 4′ sides, there is also another 8″ x 16″ vent. I’ve even let the 36″ entry door wide open, and the “puff-back” still happened. Do you think I still need more “vent?”

          I will call manufacturer while waiting for your response : )
          
          

          • Dariusz Rudnicki says:
            June 20, 2011 at 1:34 pm

            
            

            Hello,
            It looks like there’s enough of fresh air in that room and since you’ve clarified that second “explosion” it seams to be ignition delay issue. Let me know “verdict”. Thank you.
            
            
12. Dave says:
    June 9, 2011 at 10:10 am

    
    

    My newish (last 2 years) water heater as recently has been giving me some challenges. The pilot routinely goes out, if the A/C is running and the heater kicks on the exhaust does not go up the vent pipe and instead is pulled into the house. We recently replaced a very drafty sliding glass door with one that is energy star, tightening the house (so much so I often can’t hear my dog barking to be let back in). If I smell the fumes I turn off the AC fan the fume begin to vent properly than I am able to turn the AC back on, not the best solution but an effective one.

    My question is ….. Is this a water heater issue or HVAC or chimney issue? The furnace/ac unit is located off the kitchen sharing the closet with the water heater. The new door is on the opposite wall. Really who should I call to fix it or is there something DIY that can eliminate the problem. In addition, could the Water heater be defective, (still under warranty)?

    Thanks for your insight.
    Dave M.
    
    

    • Dariusz Rudnicki says:
      June 9, 2011 at 12:00 pm

      
      

      Hi Dave,
      It appears that your house became excessively “air tight” and whenever an HVAC system starts operating, it takes away combustion air necessary for the water heater’s operation / burning process. Your newer water heater is equipped with a safety device (read my answer to Christa’s question below) which shuts off the burner / pilot whenever it senses inadequate amount of combustion air or a downdraft (created by your HVAC system).
      1. Is the utility closet equipped with a sufficient amount of combustion air providing vents – louver doors, ventilation ports between its interior and the rest of the house, exterior of the house (check combustion air article)
      2. Are there any HVAC system air return ports inside the utility closet or next to the combustion air supplying ports (if such exist)? Check this – air return and combustion air
      3. If your closet is “air tight” and its interior provides the only combustion air source for the appliances it contains, open its doors while running HVAC and monitor your water heater’s operation.

      Let me know if this helps and NO, I don’t think that your water heater is defective, it’s just its safety feature response to the insufficient air supply. An experienced HVAC professional would be the right person to call. Don’t forget to maintain a functional and up-to date CO and smoke alarms!
      
      

      • Dave says:
        June 9, 2011 at 12:10 pm

        
        

        1. Is the utility closet equipped with a sufficient amount of combustion air providing vents – louver doors, ventilation ports between its interior and the rest of the house, exterior of the house (check combustion air article)

        Yes, louvered bifold doors – four sections probably 6 ft. wide.

        2. Are there any HVAC system air return ports inside the utility closet or next to the combustion air supplying ports (if such exist)? Check this – air return and combustion air

        There is a return port around the corner none in the closet.

        I guess I need a HVAC guy.

        Thanks!
        
        

        • Dariusz Rudnicki says:
          June 9, 2011 at 1:31 pm

          
          

          If your HVAC system creates a back-draft there might be a “leak” in the air supplying ducts. Maybe an open air duct in the attic, crawlspace (don’t have enough info on your entire system). Somebody will have to look at it and find a reason of that negative pressure and “vacuum” like effect HVAC system creates. Test if opening the window or an exterior door would prevent the pilot from going out.
          
          
13. Mike says:
    May 23, 2011 at 9:18 pm

    
    

    Hi, I am adding a second hw heater to my house to serve the first floor( 2 family house). The existing water heater is 40gal natural gas, 3 inch vent to chimney about 6 feet away. The 2nd water heater will be the same, but i want to use the same vent pipe for both. Will i have to increase the vent pipe size to accomadate both? And what size do i need to increase to? Thanks!
    
    

    • Dariusz Rudnicki says:
      May 24, 2011 at 12:28 am

      
      

      Hi Mike,
      The general rule for venting two water heaters into a common connector is that its diameter must be equal or more than the larger diameter vent pipe + 50% of the smaller diameter vent pipe. In your case it would be 4.5″ or more (the closest you can get is 5″). You have a few options on the drawing. Let me know if this answered your question.
      
      
      

      • Mike says:
        May 26, 2011 at 8:57 am

        
        

        That answers my question! Thank you sir.
        
        

        • Dariusz Rudnicki says:
          May 27, 2011 at 12:38 pm

          
          

          You’re welcome Mike
          
          
14. Tony Mann says:
    May 14, 2011 at 7:09 pm

    
    

    I’ve been living in my 100 yearly old home for 5 years with the following natural gas equipment:

    Natural draft gas water heater, 14 years old,, vent sizes (from hood) 3″ into 4″ into 6″, ~ 10′, into chimney.

    Natural draft gas water heater, 14 years old, vent sizes (from hood) 4″ into 6″, ~8′ into chimney.

    Natural draft gas furnace, 24 years old, vent sizes (from furnace hood) 4″ into 5″ into 6″, L – shaped, 20′ into chimney.

    There are some rust & water stains near the water heater vent hoods. Noticed slow water drips from vent joints, lots of “calcium” on vent joints, and slight rust near screws.

    The equipment and vents are located in a crawlspace that is humid in summer and is very dry in the winter, but the temperature never falls below 50 F.

    Noticed water dripping and peak CO readings from two (Kidde Nighthawk) detectors increasing slightly since Feb 2011, CO/Gas detector went off May 14, 2011

    There is no chimney cap, but never noticed water until Feb 2011.

    Gas company visited today, confirmed CO detection, said vents/chimney were not exhausting properly, deemed installation unsafe, shut off gas.

    Gas service company rep said (on phone) “water leaks from vents” indicate chimney problem. Recommended calling a chimney company.

    Can you advise on the best steps to take so I solve the right problems?

    Here’s my guess:

    1) Get chimney inspection. Do I need to install a liner?
    2) Inspect vents and/or replace due to age? Do I replace with double walled
    3) Inspect gas equipment and/or replace due to age?

    Great website! Thanks.

    -Tony
    
    

    • Dariusz Rudnicki says:
      May 14, 2011 at 9:03 pm

      
      

      Hi and thank you Tony,
      I’m assuming that you have a masonry chimney and since it’s an older home, the chimney may not have a liner at all. Missing chimney’s rain cap worsens the situation by allowing rain water penetration and causing interior wall surface and joints deterioration. Pieces of mortar, stones / brick often fall down the chimney, start accumulating, blocking the flue, restricting exhaust gases, resulting in condensation and elevated levels of CO. Your to-do list is perfect:
      1. Chimney inspection ASAP, they will tell you what needs to be done. If it’s interior is heavily deteriorated it might require partial rebuilding (if it runs through the attic, have this section evaluated too). Chimney liner is currently required by code so if you’re performing major repairs on your chimney or replacing any of the appliances – it must be installed and appliances connected directly to the liner (rain cap is required too).
      2. I would replace furnace and water heater vent pipes with double wall type. Your crawlspace is not a conditioned space (you do not control temperature and humidity in there?)
      3. Water heaters are unpredictable, they can last for a few more years or crack tomorrow. The heat exchanger of a forced air furnace installed in a crawlspace has a tendency to deteriorate much faster due to excessive humidity and temperature variations. 20 years lifespan is typical for a regular environment installation, I’ve seen severely corroded (with holes) heat exchangers in crawlspace furnaces at 10-15 years of age – have the heat exchanger checked!

      Let me know if there’s anything else I could help you with…
      
      

      • Tony Mann says:
        May 15, 2011 at 8:39 am

        
        

        Thanks Dariusz for the quick reply and advice. With the gas shutoff, it’s a good thing the heating season is over so we’ll only have to do without hot water until I can get the chimney/gas appliance companies in.

        I don’t control the temperature in the crawlspace, it’s just well insulated due to the house being built on rock. I keep the “vent window” closed year-round and run a dehumidfier in the summer, but it’s a lost cause. That’s another issue, I’m hoping your website will answer in the future.

        By the way, what is the “white stuff” I found on the vent pipes?

        I’m sure you’ve heard this a few times, but your website/information is very useful! I’ve finally found what I was looking for about chimney caps!

        Keep up the great work!

        -Tony
        
        

        • Dariusz Rudnicki says:
          May 15, 2011 at 12:47 pm

          
          

          You’re very kind Tony , thank you…
          The “white stuff” (most likely) on the vent pipes is a result of ventilation problems / possibly clogged chimney. It is caused by moisture condensation on the interior walls of the chimney and metal vent pipe. The exhaust gasses from your appliances supposed to be carried out to the exterior through the chimney. They contain slightly acidic water vapor which (with obstructed chimney) condensates on the chimney’s interior walls and flows back down through the metal pipes reacting with galvanized metal (zinc).

          That white residue could be also a product (or partial product) of efflorescence. Rain water inside the chimney and condensation soaks into the brick / mortar / stone surface dissolving the alkaline salts. It carries the solution down the chimney, furnace/water heater vent pipe, and evaporates leaving the salt deposits on surface / joints.

          As far as sealing off the ventilation in your crawlspace – very bad. You have 3 gas burning appliances that must have a constant fresh air supply to support clean and complete combustion process. The bi-product of incomplete combustion is carbon monoxide… Ask your HVAC guy about providing calculating sufficient combustion air supply for them.

          If you decide to go ahead and replace your appliances, consider stepping up to a high efficiency furnace and power vent type water heater(s). Calculate the cost of your chimney repair + natural vent type new appliances VS capping the old chimney and using new appliances venting through the side wall of the house with PVC vent pipes.
          Good luck with your project!
          
          
15. Karl says:
    April 23, 2011 at 4:46 pm

    
    

    We just got done replacing our old water heater, and need to replace the vent pipe. Really we needed to add about 2-3 inches before it 90′s into chimney. We noticed the old vent pipe didn’t stick into the chimney really far. About how far should it extend into the chimney, or do they make a plate to seal against the chimney, and then hook the vent pipe up to it?

    The old one was just sticking into chimney (barely), and then like a mortar material around it to seal then annular gap.
    
    

    • Dariusz Rudnicki says:
      April 23, 2011 at 5:52 pm

      
      

      Hi Karl, ideally the water heater vent pipe connector should be even with the interior surface of your chimney’s flue. There are collars that can be installed against the chimney wall surface at the vent pipe penetration area. However, you have to make sure that it’s sealed properly, you can use high temperature caulking (if permitted for such applications in your area), or seal the penetration around the pipe with mortar.
      
      
      

      • Karl says:
        April 23, 2011 at 6:28 pm

        
        

        Okay, thanks. As far as sealing goes, someone gave me some firecaulk. Would that be a good sealer into the chimney?
        
        

        • Dariusz Rudnicki says:
          April 24, 2011 at 1:56 pm

          
          

          Yes Karl, fire rated caulking would be good for this purpose.
          
          
16. jay says:
    April 16, 2011 at 10:12 pm

    
    

    Just wanted to say thanks for this excellent instruction on venting. I was absolutely clueless, I had ours all wrong. But now it’s perfect thanks to this video. Thank you.
    
    

    • Dariusz Rudnicki says:
      April 17, 2011 at 2:48 pm

      
      

      You are welcome Jay, any home maintenance questions – just let me know.
      
      
17. Steve says:
    March 28, 2011 at 8:03 pm

    
    

    I have a gas water heater that vents out the chimney. The gas heater vents out the side of the house, so the water heater is the only item venting through the chimney. the chimney above the roof is in very poor condition. Here’s my question, can I disassemble the chimney to just below the roof boards and vent the water heater a few feet above the roof material using a liner of some sort. The chimney “liner” used to vent the water heater would be metal and I’d like to use some kind of flange similar to what’s used for for soil stack to keep it water tight. Is that within the realm of possibilities and code compliance
    Thanks.
    
    

    • Dariusz Rudnicki says:
      March 28, 2011 at 8:45 pm

      
      

      Hi Steve,
      1. You can use your old chimney as a chase for the new water heater vent pipe. However, you‘d have to run a B-Vent (double wall pipe) from the point where the water heater vent pipe penetrates the chimney wall, through the attic and above the roof. You’d have to install a vent pipe roof flashing at the surface penetration. If you have a corbelled chimney (angled) within the attic, assembling a b-vent pipe inside it would not be possible.
      2. You’d have to consult this second option with a local building department (HVAC division) or / and HVAC contractor. Run a flexible liner inside the chimney to the point of termination inside the attic, connect a B-Vent to the liner and continue this double wall pipe through the roof.
      In this configuration however, the chimney section inside the house and within the attic would have to be repaired, tuckpointed, sealed, closed-off properly around the B-Vent to flex liner connection (so the connection remains within the chimney walls). Due to some safety concerns this may not be approved by your local jurisdiction.
      
      
18. Curtis says:
    March 22, 2011 at 5:37 pm

    
    

    We had a new gas water heater installed a few months ago. I noticed today that the top of the tank was very hot to the touch and that the plastic ring around the outlet pipe had somewhat melted closest to the vent. I saw that the white plastic rings are also slightly melted even in the picture of a properly secured vent on this website . So, is this normal that the rings melt a little bit? The WH was installed by a plumbing team and told that the vent was good. I’ve also recently had the gas company here testing for a leak and he said the vent wasn’t leaking gases.

    When I touch the vent today, it wasn’t hot. Normally, the vent is hot up to a couple of feet from the tank.

    Thanks,
    Curtis
    
    

    • Dariusz Rudnicki says:
      March 22, 2011 at 11:43 pm

      
      

      Hello Curtis,
      Melting of the plastic ring (I’m assuming you’re asking about the water pipe union connector insulator) has not much to do with a properly secured vent / draft hood. It’s rather an indication that there might a problem with the water heater’s vent pipe or / and chimney draft. When the gas water heater burner ignites, a small amount of heat / exhaust gases is usually dispersed around the draft hood. However, this shouldn’t cause melting of that plastic, with a proper / strong draft, exhaust gases should be pulled through the vent pipe / chimney.
      The WH vent pipe / chimney drafting problems could be a result of the weather, combustion air problems inside your house, your house being too tight, some obstruction inside the chimney flue, oversized chimney, undersized chimney… So, without all those questions answered I can’t tell you what’s responsible for the melting, but it isn’t normal.

      The natural draft water heater vent pipe always becomes hot with operating burner, but there shouldn’t be heat buildup around / outside of the draft hood.
      
      
19. scott says:
    March 9, 2011 at 11:08 am

    
    

    Hi, I replaced my 10 years old water heater one year ago because I smelled some kind of metal-stink after every re-boil cycle. However, only half year without the stink smell for the new one, it comes again. I asked the contractor to check any venting problem, like draft hood, pipe, cap, etc. They said nothing wrong. After I read through your web-side. I think the problem probably in condensation and/or ventilation (drafting) capacity not enough. Please give me your advice, thanks.
    
    

    • Dariusz Rudnicki says:
      March 9, 2011 at 11:49 am

      
      

      Hello Scott,
      Could you please describe the location of your water heater, ventilation of the water heater area (is it in a closet, basement, are there any vents that provide fresh air for the combustion process, what is your water source (city water or private well) and where is that bad smell coming from – is it only near the water heater, or is it from the hot water when you open the faucet after the re-boil.
      Thanks
      
      

      • scott says:
        March 11, 2011 at 10:45 am

        
        

        Hi, my water tank is far from the water source, however is located closely at the wall corner right behind the furnace. Beside the water tank, there is a basement window, I could feel there is some fresh air getting in through the gaps. I am sure the stink smell coming out of the water heater after every re-boil cycle. It seems if water heater is just on pilot the smell becomes strong. I can tell you that, when the my old tank was removed, the metal piece inside the center of the tank (under the draft hood) was corroded half left. Once again, thanks for your attention!
        
        

        • Dariusz Rudnicki says:
          March 11, 2011 at 11:58 am

          
          

          Hi again,
          You didn’t answer my questions Scott, especially “what is your house’s water source -city water or private well?”, and that smell you’re referring to, is it only near by the water heater or / and when you open the hot water faucet.
          The metal baffle inside the water heater’s flue pipe has nothing to do with the smell, it’s there to deflect heat towards the tank wall and increase the efficiency of the burning process. Over the years it corrodes, deteriorates and sometimes falls in pieces onto the burner, which might cause problems, compromise combustion, and result in CO poisoning. The water heater itself doesn’t really smell unless there’s something that has fallen into or through the chimney flue and is burning inside it.
          However, if you’re using well water, city water from a local underground source (community well), or / and a water softener, you might need to replace sacrificial anode rod in your water heater tank. It’s a magnesium or aluminum that is wrapped around a steel core wire rod, screwed in into the WH top plate that prevents corrosion of your tank.
          Anode rods usually last 5 -6 years, which depends mostly on the quality of your water and how much of that water are you using.
          When using water softener sodium is added in the process and anode rods tend to corrode much quicker, sometimes in as little as six months if the water is over-softened. Also, well / municipal well water often contains anaerobic bacteria, which reacts with aluminum and magnesium anodes producing hydrogen sulfide gas, thus creating the rotten egg odor… (sodium from softening process makes it worse).

          If this is what you have, let me know. Otherwise, I’d look for some other source of that odor, a floor drain, open sewer line, sump / ejector pump well, etc.
          
          
20. mike says:
    February 27, 2011 at 7:20 am

    
    

    I have a nautual draft water heater can i change it to a induced draft by just adding a motor or is there something I ned to do ?
    
    

    • Dariusz Rudnicki says:
      February 27, 2011 at 1:46 pm

      
      

      Hi Mike,
      Natural draft type water heaters cannot be converted into the power vent operated appliances, unless the appliance in questions is listed / approved for such type of a ventilation. You can go over to the manufacturer’s website or simply give them a call and ask about your particular model.

      It’s all about the design of your appliance. Installing an induced draft motor on a natural draft type WH that has not been designed for it could disrupt proper combustion process, result in burner operation malfunctioning, and possible CO poisoning.

      Let me know if this helped and if you have any other questions.
      
      
21. John says:
    February 24, 2011 at 12:52 am

    
    

    The vent coming off my gas water-heater and furnance join and run at an upward angle for 5ft or so, before turning straight up though the ceiling and into the attic. It stops about 6 inches from the roof. The house is almost 7yrs old. I was just rambliing around up there the other day and noticed what appears to be a soot/carmel like subtance, both on the underside of the roof and on the blown in insulation that is laying around the vent pipe. Is this normal, acceptable?
    
    

    • Dariusz Rudnicki says:
      February 24, 2011 at 12:33 pm

      
      

      If I understand correctly, the builder forgot to put a chimney through the roof (the water heater and furnace vent pipes terminate in the attic?). If so, you are lucky to be alive and still have a house (or at least the roof). This furnace / water heater vent pipe must continue through the roof and terminate above it. Chimney’s minimum height above the roof will depend on its positioning / location at the penetration point, distance to any structure, roof slope, etc. (it’s all in my chimney posts). Get a licensed HVAC contractor, visit your local building department and find out who has approved such installation.
      
      
22. brian says:
    February 19, 2011 at 10:39 am

    
    

    Hi,

    I have a vent pipe that handles both the hot water heater and the furnace. Both connections start above the bottom of the pipe, and the problem I have is that the bottom is not capped. Can you recommend a fix for me? Do I just buy a round piece of metal and caulk it in? Do you know why a builder would not provide a bottom cap? maybe just laziness? Also, I’m worried about possible gases in the house. It’s been like this for years. Better late than never, I guess.

    Thanks,

    Brian
    
    

    • Dariusz Rudnicki says:
      February 19, 2011 at 11:51 am

      
      

      Hi Brian,
      A picture would be helpful, but I believe it is something like on the one here. You should be able to purchase a cap designed for this purpose, they come in various diameters. It doesn’t have to be caulked, it’s even better to secure it with sheet metal screws only (3-4).
      
      Occasionally, there might be some condensation developing inside the vent pipe and if you seal the cap on the bottom, it will just result in corrosion. If you look inside the pipe and it appears to be clean / no rust, there is most like no draft problems and no worries about exhaust gases backing up into the house.
      
      

      • brian says:
        February 19, 2011 at 8:56 pm

        
        

        Thanks, Dariusz!

        My situation is similar to your pic, except that mine is all sheet metal. Thanks for the expert advice – you’ve really been helpful.

        -Brian
        
        
23. Stacy says:
    January 25, 2011 at 11:44 am

    
    

    Caveat: I live in a condo, on the third floor, so all the draining, piping and infrastructure is what it is.

    I just had a ultra high efficiency water heater installed. To make a long story short, we’ve come to find out the drain (previously used only as the “emergency” drain from the drip-pan) cannot accommodate a continuous flow of water, mainly condensation from the Ultra High Efficiency unit, because it terminates outside and it freezes up every night. There are no other drainage options so they are going to swap out my new unit for one exactly like the one that was in there before, which was power-vented. Because of the angles in the utility closet, the water heater sits about 3-4 feet away from the exterior wall.

    The installer had an alternative water heater he recommended, but it did not have a power vent. I think to myself… there’s got to be some reason the builders originally put a power vent in, so we should continue to go with a power vent.

    What are the requirements for power venting? Can an non-power vented unit push 4 feet horizontally?
    
    
24. Jim says:
    December 21, 2010 at 9:39 pm

    
    

    I have just replaced a natural gas water heater and the burner flame is much too yellow. When it first fired the flame was “soft and blue” as described in the installation manual. After about ten minutes of operation the flame was much larger and nearly all yellow. According to the instructions this condition indicates a lack of combustion air and will produce excess soot. I performed the draft test using a flame at the base of the vent hood and there was a smooth steady draw toward the vent. The flame becomes smaller, more stable, and mostly blue if I pinch the gas supply valve back about 25%. The new water heater has a sealed combustion chamber with a screened combustion air intake around the bottom. The tank is 21″ in diameter with a 24″ diameter aluminum leak pan under it. The vent piping is unchanged from the old unit. Until last year the flue for the water heater was shared with the hot air furnace. Two PVC pipes connected through the wall provide combustion air and exhaust venting for the new furnace. From what I have read on your website I suspect the problem is too large of a flue for the water heater alone. I assume that operating with the gas valve pinched back will reduce the amount of heat the burner can provide and increase the recovery time. As long as the pilot is stable, the burner ignites ok, and the flame looks good do you think it is OK to operate this way until the chimney flue can be properly sized?
    
    

    • Dariusz Rudnicki says:
      December 21, 2010 at 11:23 pm

      
      

      Hi Jim,

      Partially closing the gas valve is not a good idea. WH gas regulators are designed for dealing with the amount of gas provided from the gas meter / pressure regulator / gas piping. While running a few gas appliances at the same time, the one with a partially closed gas valve might be starving for fuel and shut down or start short-cycling.

      You didn’t mention the WH draft hood, vent pipe and chimney flue diameters, so I don’t know if this is the reason for the flame color issues. Usually it is not – oversized chimney might cause back-drafting, condensation inside the chimney flue, CO poisoning, etc.

      Flame discoloration is in most cases related (like you’ve mentioned) to inadequate amount of combustion air that must be supplied to sustain complete burning, without producing CO (yellow flame does that). Check those posts:
      Combustion Air
      Combustion Air Condominium (this one refers to Chicago but applies to “everywhere”) and make sure that your water heater has a sufficient amount of air supply from within the house or exterior.
      Let me know if you have any other questions,
      Thanks
      
      
25. Lewis McDowell says:
    December 21, 2010 at 12:41 pm

    
    

    I am currently extending out a bath that will require me to swing the gas vent pipe more toward the exterior wall to enable me to move the bath tub. It appears that I can spin or turn the pipe get it where I need to at the bottom but then my roof connection is crooked. Can I add a 45 to reconnect to the roof vent? this would mean a 45 or what ever the degree is coming out of the top of the water heater then straight pipe then 45 back to line up to current roof vent stack.
    
    

    • Dariusz Rudnicki says:
      December 21, 2010 at 11:31 pm

      
      

      Hi Lewis,

      Without using vent pipe tables for your particular installation and just applying general rules, you can use 45° connectors and one 60° connector. However, to be on the safe side, you should properly calculate the entire run of your WH vent pipe. It might be OK, but it all depends on the BTU’s of the water heater, draft hood diameter, horizontal and vertical runs length + offsets.

      Without that information it’s difficult to say if what you’re doing is safe, because that additional length of the vent pipe might compromise proper drafting.

      You’d need Gama Vent Tables to perform those calculations ask ask your local building department / licensed plumbing contractor to evaluate your installation.
      
      
26. Kathy says:
    October 13, 2010 at 8:53 am

    
    

    My vent pipes are 3 1/2 inch in diameter. During high winds the pilot light goes out. Can I put a 4 inch, high wind cap on a 3 1/2 inch pipe at the roof termination?
    
    
27. Cheryl says:
    October 10, 2010 at 7:37 am

    
    

    I have a gas hot water heater, installed in 2004. Currently both the furnace and hot water heater are vented into an exterior brick chimney. I am in the process of purchasing a new hgh efficiency furnace. The furnace installer is telling me since the furnace will be vented out the wall, there will not be enough draw for the hot water tank to be safely vented up the chimney. He said carbon monoxide will back into the basement. He suggested I add a liner to the chimney, or purchase a new power venting hot water tank. Another installer has said that is not always true. How do I know if I need to replace the hot water tank, or if it is venting properly
    
    

    • admin says:
      October 10, 2010 at 10:02 am

      
      

      Hi Cheryl,
      You can go to my post Water Heater Chimney Flue Sizing for a general answer. To calculate exactly the size of the required chimney diameter that will accommodate your water heater, you’d need to use Gama Tables and do some measurements of your installation. There is an easy to follow guide here – Hart & Cooley Type B Gas Vent & All-Fuel Chimney Sizing Guide – open the lower one of those 2 pdf files, go to page #8, it starts at “Single-Appliance Vent Systems”.
      There’s a 1” difference in the max. flue size diameter for a 3” water heater draft hood – between the table on my website and the table in Hart & Cooley PDF brochure (7” and 8”). I’d rather go with 7” maximum (if possible, keep the liner size closer to the minimum required diameter instead of a max.), especially with an exterior chimney.

      Let me know if you need some help with it.
      
      
28. Clay says:
    October 4, 2010 at 7:12 pm

    
    

    Should gas water heaters be raised off of the floor?
    
    

    • admin says:
      October 7, 2010 at 10:48 am

      
      

      Hi Clay,
      I’ve put up together a little more information about raising the water heater – Gas Water Heater Raised Above the Floor
      
      

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