Rheem Electric Domestic Water Heater - Manual (Page 26)

CONNECTIONS – PLUMBING
26
EXPANSION CONTROL VALVE
Local regulations may make it mandatory to install an expansion control valve
(ECV) in the cold water line to the water heater. In other areas, an ECV is not
required unless the saturation index is greater than +0.4 (refer to
“Water
Supplies” on page 33). However, an ECV may be needed in a corrosive water
area where there are sufficient quantities of silica dissolved in the water.
The expansion control valve must always be installed after the non return valve
and be the last valve installed prior to the water heater
(refer to diagram on
page 23 ) . A copper drain line must be run separately from the drain of the relief
valve.