House Water Heater Venting, How To Do It Right
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To fully understand house water heater venting I highly recommend reading House Brick Chimney Problems & Gas Water Heater and Furnace Chimney Flue Sizing posts – several of the water heater vent pipe conditions described below depend on properly operating and installed chimney!
There are two common types of gas water heater vents:
- natural draft – explained below
- induced draft / water heater PVC pipe venting / power venting
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, because they serve very important purposes and if not installed correctly, carbon monoxide gases may be expelled into the living space.
- Gas water heater draft hoods provide additional air for the combustion process gases, to be properly pulled out from the burner chamber (base of the water heater), into the water heater vent pipe and the chimney
- Gas water heater draft hoods act as a device, which in case of down-draft (a condition which forces air / wind back into the vent pipe / chimney), prevents air from extinguishing the gas burner.
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.
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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.
House Maintenance Comments
4 Responses to “House Water Heater Venting, How To Do It Right”
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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!
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.
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?
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.