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There are two common types of gas water heater vents:
Natural is still dominating, and as long as the property has a chimney dedicated for use with gas burning appliances, you can use this type of venting.
Typical connection of the gas water heater vent pipe would look more or less like one on the picture (one of the problems with this connection – missing screws at draft hood). There might be several variations… some good, and some bad of course.
Assuming, that you don’t know anything about this subject, this is how the gas water heater venting should be installed:
On top of gas water heater, in its center section, right above water heater vent, you should have a draft hood installed. It sits on 3-4 short legs, sometimes secured to the water heater top plate with screws, or (depending on design) has its legs shaped like pins or hooks at the end, inserted into the holes in water heater top cover.
For the gas water heater vent to operate properly its Draft Hood Has to be Centered over the vent hole, and its legs must be straight – any displaced or deformed draft hoods should be serviced / replaced if necessary. They serve a very important purpose and if not installed correctly, carbon monoxide gases may be expelled into the living space. I’m pretty sure you’re aware how dangerous Carbon Monoxide can be…
Gas water heater draft hoods come in different sizes, and if you are replacing water heater, make sure, that the draft hood and the vent pipe match the new appliance. If the draft hood that came with your water heater has a top opening diameter designed for 3″ vent pipe, and you have 4″ vent pipe installed, use reducing connector.
However, if the gas water heater draft hood is larger, designed for a 4″ pipe – do not downsize it! / DON’T install reducing connector from 4″ draft hood to 3″ water heater vent pipe just to accommodate an old venting system.
Replace the smaller size vent pipe with a proper / required size (most 30 gallons, 40 gallons, and 50 gallons water heaters use 3″ diameter vent pipe, some 50 gallons might require 4″, 75 gallons and more will call for 4″ and more – follow manufacturer recommendations and local code requirements).
Draft hood and water heater vent pipe connections should be secured with sheet metal screws – three per connection on a single wall pipe are recommended.
Gas water heater vent pipe material - for natural draft type just use galvanized steel pipe and don’t experiment with aluminum pipes, food cans with removed both ends, stainless steel sections, blue stove pipes, high temperature plastic tubing, flexible pipes…, etc.
Gas water heater vent pipe must continuously run upward towards the chimney entrance, raising not less than 1/4″ per linear foot, to provide proper draft. Some installation might be a significant challenge, or even become impossible, due to a water heater height and chimney flue connection level, in those cases, induced draft motor equipped water heater should be used.
Gas water heater vent pipes should be monitored periodically for corrosion and deterioration. Problems with proper drafting, and chimney conditions usually cause galvanized pipes to corrode. Small holes start appearing on their surface – most common areas are along the bottom portion and on connectors. At some point, corroded gas water heater vent pipe wall becomes very soft, and might fall apart when under even slight pressure.
Corroding gas water heater vent pipes should be replaced as soon as possible, to prevent possibility of exhaust fumes / Carbon Monoxide contamination.
Single wall gas water heater vent pipe can not be installed closer than 6″ from combustible materials (floor / wall framing, paper, etc.) such installation could create pyrophoric conditions and a fire-hazard (material will ignite spontaneously at significantly lower temperature if constantly exposed to heat).
Single wall gas water heater vent pipes can not be used in unheated areas like attic or garage (even if only partially penetrating that space) , because such installation will cause excessive condensation on vent pipe walls and compromise proper drafting – double wall pipe / B-vent type is required.
Single wall gas water heater vent pipe can not be used inside the walls, ceilings and any inaccessible areas – double wall type vent pipe / B-vent must be installed.
There’s more about house water heater venting in vent pipe clearances post – enjoy it.
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dennis
1 week ago
I have two natural gas water heaters 60 gal. One up stairs and one downstairs (two apartments) They are vented on one 4″ line the pilot light will go out often on the water heater upstairs when the heat or ac comes on upstairs.If I leave a window open about 2″ next to the water heater it will not go out. Is the vent pipe to small for the water heaters?
admin checkthishouse.com
1 week ago
Hi Dennis,
There might be several reasons for the water heater pilot light to go out. Since you’ve mentioned that opening of the window prevents the WH burner pilot from being extinguished, it seems like there’s no sufficient combustion air supply for the area your gas burning appliances are located in.
Also, your HVAC system supply and return ducts / register openings may not be balanced properly (not enough return ports), and / or returns have been positioned in such way, that they are (whenever the HVAC system kicks in) sucking the air from the exterior / through the WH’s vent pipe / draft hood. This sometimes happens if the HVAC system return port has been installed next to the combustion chamber (burner area) – minimum 10′ distance between the air return and combustion chambers is required – assuming that you have sufficient combustion air supply to that area.
As far as the water heater vent flue pipe size, the requirement for two water heaters using a common vent pipe is that the vent pipe diameter starting from the connection of the water heater closest to the discharge end must be the size of the largest draft hood + 50% of the smaller draft hood diameter.
If both water heaters have a 3″ diameter draft hoods, 4″ diameter vent pipe is too small – you’d need a 5″ diameter vent pipe (I don’t think they make 4.5″). For two 4″ diameter draft hoods, the common vent flue pipe diameter would have to be 6″. However, those calculations also depend on the number of bends / elbows installed on the vent pipe, and tables usually supplied with the water heater should be used for exact calculations.
If your water heaters are standing next to the chimney, one 60°, and bends up to 45° (as an offset) are permitted without using the tables.
Let me know if this helped and check “combustion air” post – extremely important.
Steve
2 weeks ago
I have a problem with bats in my basement and back entry/ mudroom. The only place i can see that they would be getting in is down the chimney, only my water heater is venting out the chimney and to try and control the bat problem I want to put some window screen in the vent pipe to stop them. My question being is it safe to do this or will it restrict airflow too much to allow proper ventilation?
admin checkthishouse.com
2 weeks ago
Hi Steve,
Do not put any window type screen inside the vent pipe – it is not designed for this purpose and it will significantly cut down the chimney drafting capacity. Over time, small screen can become clogged with burning process deposits and dust – it’s dangerous. Instead, install a listed / approved for this purpose screen on top of the chimney. There are various types of those chimney screens, some are integrated into the chimney cap, others can be added around the existing cap. Just search for “chimney cap”, or “chimney screen” in your browser. If you have a tall, unsupported, hard to access chimney, do not lean the ladder against it!
Kate
4 weeks ago
Hi –
I also have a question. I’m a new homeowner and recently got a 40 gallon gas water heater that is a natural draft type. The old water heater had a 3″ vent pipe. The new one was installed using the same 3″ vent pipe but it failed inspection because NJ state code says it has to be 4″. Unfortunately the 3″ vent pipe goes into a 3″ liner in my chimney so the plumber came back and gave me an estimate of $1,100 to switch the chimney liner and vent pipe from 3″ to 4″. I asked if it could vent directly into the chimney (no liner) and he said that it would be too big. Are there any other options? $1,100 is A LOT of money on top of the cost of a new water heater. Could we install the chimney liner ourselves? Thanks for your help!
admin checkthishouse.com
4 weeks ago
Hi Kate,
With a 3″ diameter water heater draft hood you can vent in up to a maximum 7″ diameter chimney. Your plumber has already confirmed that it would be too large with that 3″ liner removed and in order to keep using that chimney, it needs to be re-lined (chimneys cannot be used without liner anyway).
You can do it yourself for as long as your local building department will allow you to. They might simply say that the installer has to be licensed to perform such work.
Assuming that they let you do it, there are two things that could make self-installation difficult: the shape of your chimney (some of the older chimneys run partially on an angle – corbelled), and access to the top opening – tall, unsupported chimney would most likely require scaffolding installation – you have to get there from the top, and you should not lean the ladder against it, it’s dangerous.
• I would suggest to insulate the liner if possible (your jurisdiction might require it), check your local hardware stores for prices, size the liner accordingly to its length, number of bends / there should be tables provided with the WH and / or liner manufacturer.
The other options…
Unfortunately they are more expensive because you have already purchased the water heater. If it can be returned, and exchanged for a power vent equipped water heater or a tankless type:
• The new WH with installation would most likely be over $1000.00
• The tankless type WH with installation close to $2000.00 (or more depending on the model).
Natural draft type water heaters cannot be converted into the power vent operated appliances that discharge exhaust gasses horizontally / through the side wall – the appliance must be listed for such type of ventilation, and your local building department wouldn’t allow it.
Let me know if there’s anything else I could help you with.
Exhaust Venting : RTI Technologies RTIEV-1 Exhaust Ventilation System
2 months ago
[...] read more at: http://www.checkthishouse.com [...]
Scott
3 months ago
I’m hoping to bypass my chimney flue for my hot water heater. Can I redirect my exhaust from my hotwater heater to the side of my house?
Similar to how my furnace it doing it.
admin checkthishouse.com
1 month ago
You could do that only if:
• it is a direct vent type water heater – it takes all combustion air from exterior. It might be double pipe design (two pipes visible inside) changing to one pipe at wall penetration, or pipe within the pipe inside with a special termination connector on exterior
• many tankless water heaters can be vented through the side wall
• power vent type water heater can be also vented through the side wall (PVC vent)
If your water heater has a draft hood (natural draft type), it is required by code to be connected to the chimney.
Give me the model # and brand of your appliance if you’re not sure, or email me a picture of it.
lisa
1 year ago
my water heater is gas. had to replace it. friend had one but it is eletric. boyfriend used it. water isnt getting real hot. warm. how safe is this?
admin checkthishouse.com
1 year ago
Lisa…, I’m not sure what is your questions related to… electric water heaters are as safe as the gas water heaters. Depending on the water heater size, it might have one or two heating elements. If one of them fails (usually the bottom one first), it will take much longer to heat-up that tank of water. Each heating element has a small adjustment screw / thermostat with a temperature scale. By turning the screw you will lower or increase the water heater tank output temperature. EXTREMELY IMPORTANT:
1. before any attempt to change the temperature, you must TURN OFF the electric water heater power supply! – the thermostat is concealed behind a metal plate, often covered with insulation, and there might be some exposed high voltage wires
2. It takes just one second to burn your skin with 160F water temperature, 1/2 minute at 130F. The maximum water temperature setting suggested by the Consumer Product Safety Commission is 120F (about 10 minutes of exposure will give you 3rd degree burns). 110F is safe but not hot enough for some of us… Be careful.
Laura Courier
1 year ago
Hello,
I have a question, Our gas water heater is in a cabinet inside. The cabinet is old and has venting grills on the bottom and top of the door. When we had the water heater replaced a few years ago, it was properly vented to the outside. We are going to replace the cabinet now and I was wondering, do we need to vent the door again now that the heater has been vented to the outside? I hate to put holes in the new door if it is unnecessary. If we do need to vent the door, do you know what size the holes need to be for code? Currently they are 14in wide and 8in high. I would appreciate your expertise on this!
admin checkthishouse.com
1 year ago
Hi, unfortunately you do need those holes, if you follow this link, I’ve explained everything in more detail – Combustion Air for Fuel Burning Appliances. Proper venting of your water heater and your safety depends on air supplied for its combustion. If your water heater closet / cabinet has an exterior wall (to the outside), there’s an attic above or basement / crawlspace underneath, you’ll have more choices which could save your new door. Let me know or check the post linked above in a couple of days for more info.