Domestic Side Piping

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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

Installation & Operation Manual

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.

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.

If an expansion tank is used, do not put NOTICE any valves between the expansion tank

and tank inlet.

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.

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.

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.

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