American Water Heater 6510238 - Manual (Page 13)

Please note the following:
DO NOT install this water heater with iron piping. The
system should be installed only with piping that is
suitable for potable (drinkable) water such as copper,
CPVC, or polybutylene. DO NOT use PVC water
piping.
DO NOT use any pumps, valves, or fittings that are
not compatible with potable water.
DO NOT use valves that may cause excessive
restriction to water flow. Use full flow ball or gate
valves only.
DO NOT use 50/50 tin-lead solder (or any lead based
solder) in potable water lines. Use 95/5 tin-antimony
or other equivalent material.
DO NOT tamper with the gas valve/thermostat, igniter,
thermocouple, or temperature and pressure relief
valve. Tampering voids all warranties. Only qualified
technicians should service these components.
DO NOT use with piping that has been treated with
chromates, boiler seal, or other chemicals.
DO NOT add any chemicals to the system piping
which will contaminate the potable water supply.
Closed System/Thermal Expansion
Periodic discharge of the temperature and pressure
relief valve may be due to thermal expansion in a closed
water supply system. The water utility supply meter may
contain a check valve, backflow preventer or water
pressure reducing valve. This will create a closed water
system. During the heating cycle of the water heater,
the water expands causing pressure inside the water
heater to increase. This may cause the temperature
and pressure relief valve to discharge small quantities
of hot water. To prevent this, it is recommended that a
diaphragm-type expansion tank (suitable for potable
water) be installed on the cold water supply line. The
expansion tank must have a minimum capacity of 1.5
U.S. gallons for every 50 gallons of stored water. Contact
the local water supplier or plumbing inspector for
information on other methods to control this situation.
Important: Do not plug or remove the temperature
and pressure relief valve.
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