Firstly lets explain what is happening with your water heater – as water is heated it expands and has to go somewhere – part of the safety features of mains pressure water heaters are the pressure and temperature relief valves that are fitted to them. When the heater is operating water SHOULD dribble out of the hot water relief valve otherwise the pressure build up inside the system would cause a dangerous condition to eventuate that could in fact cause an explosion.
One sure way to protect the system is to install a cold water relief value on the inlet water supply pipe close to the cylinder – this valve should be rated at 80% of that of the hot water relief valve. The outlet of the cold water relief valve should be directed to an outside gully trap where it will cause no harm to anything when it allows water flow during heat up periods.
In an case according to Rheem’s manuals the valves should be “eased” at regular intervals to ensure their safe and effective operation continues.
Hope this information is of assistance to you.
Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians