Lochinvar SDT/SET065 - 119 operation manual Domestic Side Tank Piping, Basic Domestic Piping

SDT/SET Installation & Operation Manual

4Domestic Side (Tank) Piping

Basic Domestic Piping

Figure 4-2 on page 15 shows typical domestic water piping for a tank. The function of the components shown are as follows:

a.Shut-off valves (recommended) - Used to isolate the tank for servicing.

b.Backflow Preventer (required by some codes) - Used to prevent water from backing out of the tank and into the main potable water supply in the event that inlet water pressure drops.

c.Expansion Tank (required for thermal expansion)- his expansion tank absorbs the increased volume caused by heating water.

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	When an expansion tank is used, do not
	put any valves between the expansion
	tank and tank inlet.

d.Unions (recommended) - Used to disconnect the tank in the unlikely event that this is necessary.

e.Drain (required) - Used to drain the tank for inspection or servicing.

Domestic Water Piping for Distant Fixtures

In some cases the furthest fixture may be quite distant from the tank. Such an installation would result in an unacceptable delay before hot water reaches these distant fixtures. Even if all the fixtures are relatively close to the tank, the building owner may want hot water at all fixtures as soon as they are opened.

To prevent delays, return circulation piping with a check valve that allows flow to the inlet of the tank. This should be installed on each branch circuit at the farthest fixture or device, so that hot water is supplied upon demand.

Because hot water is always circulating in the hot water branch, the entire branch should be insulated to prevent excessive heat loss.

Multiple Tank Domestic Water Piping

The two pipe reverse return piping uses more pipe than the two pipe direct return piping, but the flow is more balanced and even in the two pipe reverse return piping layout (see FIG. 3-4).

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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