ECO
Installation Instructions and Use & Care Guide
11
4.3.
THERMAL EXPANSION
Determine if a check valve exists in the inlet water line. It may have been installed in the cold water line as a
separate backflow preventer, or may be part of a pressure-reducing valve, water meter, or water softener. A
check valve located in the cold water inlet line can cause what is referred to as a “closed water system”. A
cold water inlet line with no check valve or backflow prevention device is referred to as an “open water
system”.
As water is heated, it expands in volume and creates an increase in the pressure within the water system.
This action is referred to as “thermal expansion”. In an open water system, expanding water which exceeds
the capacity of the water heater flows back into the city main, where pressure is easily dissipated.
A closed water system prevents the expanding water from flowing back into the main supply line, and the
resulting thermal expansion can create a rapid and dangerous pressure increase in the water heater and
system piping. This pressure increase can quickly reach the safety limit of the relief valve, causing it to
operate during each heating cycle. Thermal expansion, and the resulting rapid and repeated expansion and
contraction of components in the water heater and piping system, can cause premature failure of the relief
valve and possibly the water heater itself. Replacing the relief valve will not correct this problem.
The suggested method of controlling thermal expansion is to install an expansion tank in the cold water line
between the water heater and the check valve. The expansion tank is designed with an air cushion built in
that compresses as the system pressure increases, thereby relieving the thermal expansion and eliminating
the repeated operation of the relief valve.
Other methods of controlling thermal expansion are available. Contact your installing contractor, water
supplier, or plumbing inspector for additional information regarding this subject.
4.4.
WATER CONNECTIONS
The installation of unions or flexible copper connectors is recommended on the hot and cold water
connections so that the water heater may be easily disconnected for servicing if necessary. The HOT and
COLD water connections are 3/4
"
.
NOTE:
Install a shut-off valve in the cold water line near the water heater. This will enable easier service and
maintenance of the water heater.
IMPORTANT:
Do not apply heat to the HOT or COLD water connections will permanently damage the
connections and tubes.
Please note the following:
The system should be installed only with piping that is suitable for potable (drinkable) water such as
copper, CPVC, or polybutylene. This water heater must not be installed using iron piping or PVC
water piping.
Use only pumps, valves, or fittings that are compatible with potable water.
Use only full flow ball or gate valves. The use of valves that may cause excessive restriction to water
flow is not recommended.
Use only 95/5 tin-antimony or other equivalent solder. Any lead based solder must not be used.
Piping that has been treated with chromates, boiler seal, or other chemicals must not be used.
Chemicals that may contaminate the potable water supply must not be added to the piping system.
