American National Standards Institute
Agency that sets standards for safety of gas
Anode or Anode Rod
Sacrificial component made of aluminum,
magnesium, or other alloys, that is corroded by electrical currents
in order to protect the inside of the tank.
British Thermal Unit (BTU)
The amount of energy required to heat one pound
of water by 1°F.
Poisonous gas that is a byproduct of incomplete
combustion. Carbon monoxide is harmful or fatal to breathe and must
be vented to the outdoors. Excessive carbon monoxide is an
indication of poor combustion. The cause must be investigated and
Part of the gas water heater, located in the
jacket base assembly, where the burner is located and combustion
Parts that measure tank temperature, direct the
unit to begin heating and provide safety controls to prevent
overheating or other unsafe operating conditions.
Water connectors that reduce the flow of
electricity related to galvanic corrosion, from the house piping to
the water heater.
Department of Energy (DOE)
Government agency that regulates water heater
Energy Cutoff Switch (ECO)
Gas water heater safety device that shuts off the
gas supply to the unit if water temperature exceeds 190°F. The ECO
is a single-use switch and requires complete replacement of the
entire thermostat if activated.
Overall efficiency of a water heater calculated
by testing tank draw efficiency, recovery efficiency, and standby
efficiency using the DOE protocol.
Energy Guide Label
Yellow label displayed on every water heater that
compares that model's energy use to similar models.
A tank installed on the incoming water line that
absorbs expanding water and prevents pressure build up inside the
The vertical pipe in the center of a gas water
heater designed to conduct rising heat into the water and direct
combustion by-products out the vent.
A device located in the center of the flue that
slows the rising heat and gasses produced by the combustion
process, enabling the water to absorb more heat.
Gallons Per Hour (GPH) Recovery
The amount of water, in gallons per hour, that a
water heater can raise by 90° increase in temperature.
Mixing Valve (Tempering Valve)
Device that mixes cold water with hot water
supplied to general use fixtures.
Threaded fittings provided on some models for
incoming and outgoing water pipe connections. Most models utilize
3/4" water connections.
Gas by-product of combustion that is harmful to
the earth's atmosphere.
A small flame that stays lit all the time and
ignites the burner flame.
Water that is suitable for drinking because it
contains nothing harmful.
Salts formed and deposited inside the water
heater or on fixtures. Sometimes referred to as lime deposits.
Very high temperatures at the top of the water
heater tank caused by increased cycling of the burner or heating
elements during short draws of water.
Temperature and Pressure Relief Valve (T&P
Safety device that releases hot water when
temperatures inside the tank reach 210°F, or when pressure exceeds
Expansion of water as it is heated.
Electronic device used in place of a mechanical
thermostat that measures water temperature.
Safety device that generates a small electrical
current used to energize a safety magnet inside the gas valve.