Rheem 300 series - Manual (Page 9)

REGULAR CARE
9
EXPANSION CONTROL VALVE
In many areas, including South Australia, Western Australia and scaling water
areas, an expansion control valve is fitted to the cold water line to the water
heater. Water will flow from its drain line during the heating period.
Operate the easing lever on the expansion control valve once every six
months. It is very important you raise and lower the lever gently. The
expansion control valve should be checked for performance or replaced at
intervals not exceeding 5 years, or more frequently in areas where there is a
high incidence of water deposits.
SERVICING
For safe and efficient operation, the water heater should be serviced annually
by your nearest Rheem Service Department or their Accredited Service Agent.
Only genuine replacement parts should be used on this water heater.
Warning: Servicing of a gas water heater should only be carried out by
authorised personnel.