Installation & Operation Manual
10
3
Piping
Domestic Side Piping
Basic Domestic Piping
Figure 3-5 on page 12 shows typical domestic water piping for
a tank. All components except the control are provided by the
installer. The function of the components shown are as
follows:
a.
Shut-off valves (recommended) - Use to isolate the
tank for servicing.
b.
Backflow Preventer (required by some codes) - Use to
prevent water from backing out of the tank in the event
that inlet water pressure drops.
c.
Expansion Tank (required when a backflow preventer is
used) - This expansion tank absorbs the increased
volume caused by heating water. If a backflow
preventer is installed, this expansion tank is required
because the increased water volume will otherwise have
no place to go and the T & P valve will open.
Use an expansion tank designed for use on domestic
water systems. Refer to the expansion tank
manufacturer’s literature for the proper size expansion
tank to use.
NOTICE
If an expansion tank is used, do not put
any valves between the expansion tank
and tank inlet.
d.
Unions (optional) - Use to disconnect the tank in the
unlikely event that this is necessary.
e.
Drain (required) - Used to drain the tank for
inspection or servicing.
Tank Piping with a “Temperature Limiting
Valve”
Usually, the maximum temperature of the outlet water will stay
near the setting of the tank control. In some cases, however, hot
water usage patterns can cause the outlet water temperature to
rise significantly above the control setting.
The temperature of water going to the fixtures may be more
carefully controlled through the use of a thermostatic mixing
valve. This device blends a controlled amount of cold water
with the hot water leaving the tank so that water at a more
constant temperature exits the mixing valve. Anti-scald mixing
valve piping is illustrated in FIG.’s 3-1 thru 3-3.
WARNING
An anti-scald mixing valve does not
eliminate the risk of scalding.
*
Set the tank thermostat as low as
practical.
*
Feel water before bathing or
showering.
*
If anti-scald or anti-chill protection is
required, use devices specifically
designed for such service. Install
these devices in accordance with their
manufacturer’s instructions.
Multiple Tank Domestic Water Piping
Figure 3-4 illustrates the recommended method of piping the
domestic water side of several tanks together. All tanks are
piped in true parallel. Total domestic pipe lengths must be the
same from point of tank exit to the common “T” to ensure an
equal draw from each tank.
Each tank must have its own T&P valve. It is recommended that
each tank be equipped with its own isolation valves, unions, and
drains so that one tank may be removed from the system. If
local codes require a backflow preventer, check with the
appropriate authority to find out whether one backflow
preventer may be used for tanks or each tank must be equipped
with its own backflow preventer. If each tank must have its own
backflow preventer, each tank must also have its own expansion
tank. If a common backflow preventer is permitted, an
expansion tank must be sized to accommodate the expansion
volume of all tanks.
