Rheem HG Thermal Expansion, Water Supply Connections, Typical Installation

WARNING: The water heater should not be installed in a space where liquids which give off flammable vapors are to be used or stored.

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 back flow preventer, or it 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 back flow 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 the pressure is easily dissipated.

A “closed water system”, however, prevents the expanding water from flowing back into the main supply line, and the result of “thermal expansion” can create a rapid and dangerous pressure increase in the water heater and system piping. This rapid pressure increase can quickly reach the safety setting 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 heater itself. Replacing the relief valve will not correct the 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 (see illustration below). The expansion tank is designed with an air cushion built in that compresses as the system pressure increases, thereby relieving the over pressure condition and eliminating the repeated operation of the relief valve. Other methods of controlling thermal expansion are also available. Contact your installing contractor, water supplier or plumbing inspector for additional information regarding this subject.

Safety Instructions Installation Instructions Operating Instructions

IMPORTANT: Do not apply heat to the HOT or COLD water connections. If sweat connections are used, sweat tubing to adapter before fitting adapter to the cold water connections on heater. Any heat applied to the cold water supply fittings will permanently damage the dip tube.

5 feet

from the

ground

minimum

Water Supply Connections

Refer to the illustration below for suggested typical installation. 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 clearly marked and are 3/4″ NPT on all models. Install a shut-off valve in the cold water line near the water heater.

Typical Installation

Vent connector		Pitch up 1/4″
	Union
to chimney		per foot

Heat trap						Draft hood
6″ minimum						Anode
Hot water outlet	HOT					Union
	F E I L E	R
to fixtures				COLD
			L A	V
		E V
Temperature and
pressure relief valve
Manual gas shut-off						Heat trap
		Shut-off				6″ minimum
To gas supply				valve		To cold water
						supply
Ground joint union						Shut-off valve
Sediment trap					Thermal expansion
					tank (if required)
Cap						Relief valve
					Drain	discharge line to
						suitable open drain.
Thermostatic gas valve					valve
Jacket door

Care and Cleaning Troubleshooting Tips Customer Service

6″ air gap 9

Auxiliary catch pan