Rheem Electric Domestic Water Heater Installation And Owner's Manual page 22

INSTALLATION
Circulated Hot Water Flow and Return
Continuous Electric Water Heater
Off-Peak or Time Controlled Electricity Supply
A single or twin element electric water heater connected to an Off-Peak
LEGEND
electricity supply should not be installed as part of a circulated hot water flow
and return system in a building. The benefits of the Off-Peak electricity supply
will be significantly reduced.
If a circulated flow and return system is required, it is necessary to bypass the
Off-Peak electric water heater and install a secondary water heater connected
to the hot water flow and return line and supplied from the Off-Peak electric
water heater. Refer to the diagram on page 22.
Circulated Hot Water Flow and Return System
Off-Peak Electric Water Heater
LEGEND
22