Water heater
What it is
Traditional gas water heaters with draft hoods are prone to spillage and backdrafting. They should be avoided.
The most common type of corrosion in residential water heaters is galvanic corrosion, where differences in types of metals or even impurities in the tank itself cause corrosion cells to occur.
A whole house fan is capable of pulling large quantities of air from the home and, particularly if not enough windows are open, may easily backdraft a water heater located inside a louvered closet door.
If the water heater lacks pre-installed check valves, install a check valve or heat trap on both the cold water inlet and hot water outlet piping as close to the tank as possible to reduce heat loss from natural convection.
U.S. Department of Energy · Pacific Northwest National Laboratory · ENERGY STAR
Its parts
- Burner
- A gas tankless water heater’s basic components include a high-powered burner, fan, and heat exchanger. When a hot water tap is turned on, cold water enters the unit from the cold water supply and a sensor detects the water flow; then it activates a heating device, which raises the water temperature to a preset level.
- Basic components of a gas tankless water heater include a high-powered burner, fan, and heat exchanger; condensing gas water heaters also have a secondary heat exchanger and a piped air intake to the sealed combustion chamber.
- Most tankless water heaters are sealed combustion, meaning that combustion air for the burners is brought directly from outdoors and the combustion fumes are exhausted to outdoors without any interaction with the living space air.
- Draft hood
- If your water heater has a draft hood then it is a natural draft water heater.
- A draft hood is a flanged hood at the base of the flue pipe above the gas water heater tank (Figure 3).
- Flue
- With a sealed combustion chamber and separate air intake, it is almost impossible for these types of water heaters to backdraft harmful flue gases back into the house.
- Anode rod
- Because the glass lining is inherently imperfect, and to incorporate redundant protection into water heaters, almost all manufacturers also include an anode rod in the design of storage water heaters.
- tankless water heaters are constructed of less galvanically active metals to protect them from corrosion. This is because tankless water heaters cannot employ an anode rod to protect against corrosion.
- Often tanks leak due to deterioration of the sacrificial anode rod and subsequent corrosion of the tank. Most homeowners are not aware of their water heater’s anode rod or the fact that they are supposed to inspect it (Turriff and Bailey 2010).
- Sediment
- For electric storage water heaters, the efficiency of the water heater was maintained at the rated value until sediment reached the bottom element and buried it, causing the bottom element to overheat.
- Mixing valve
- A thermostatic mixing valve (TMV) can be used to regulate the temperature at plumbing fixtures to prevent hot water scald potential. The mixing valve will reduce the point-of-use water temperature by mixing the hot water from the water heater with a cold water supply.
If it may be unsafe
If you smell gas, leave the house and call Peoples Gas at 866-556-6002 or 911 from outside. If your CO alarm sounds or anyone feels sick, leave and call 911 from outside.
AirLogic is not an emergency service.
Related pages
- Glossary: Water heater
Its entry, and the guide's pages that use it.
- Gas water heaters
Gas water heater types, burning air, venting and the signs of backdrafting
Sources
- U.S. Department of Energy. BSC Information: Sealed Combustion for All Climates.
- Pacific Northwest National Laboratory. Impacts of Water Quality on Residential Water Heating Equipment (PNNL).
- U.S. Department of Energy. Whole House Fan: How to install and use a whole house fan (U.S. Department of Energy technology fact sheet, DOE/GO-10099-745).
- ENERGY STAR. ENERGY STAR NextGen Certified Homes June 2024 Heat Pump Water Heater Guide.
- U.S. Department of Energy. Tankless WHs Gas Fired.
- U.S. Department of Energy. Gas-Fired Tankless Water Heaters.
- U.S. Department of Energy. PNNL Building Science: Look for Signs of a Gas Water Heater Backdrafting.
- U.S. Department of Energy. Gas Storage Water Heaters.