Leaking hot water cylinder or valves
Beware that hot water cylinders that are rusty around the bottom or bulging on the side are almost ready to start leaking.
If water is leaking from the electrical box or plastic caps on the cylinder, take caution as some cylinders may burst, spraying boiling water over cupboards and people.
Turn the water and power off, then call a plumber.
Temperature / Pressure Relief Valve:
This valve is a safety valve and is found near the outlet of your hot water cylinder. The pressure relief setting varies from one cylinder to another and can range from 600 to 1200kpa.
The temperature relief is set at 99 C as once it gets to 100 C water turns to steam and will damage your hot water system.
This should be tested and/or replaced every five years.
NEVER CAP OFF A LEAKING RELIEF VALVE, as the cylinder will expand out of shape or explode (as seen on Myth Busters).
Expansion Cold Water Valve:
This valve is found on the inlet side of the hot water cylinder. The pressure relief setting is set lower than the T/P valve.
It works as a first stage relief valve as the cold water in the cylinder expands. It is usual for the ECV to relieve pressure while the water is heating. The flow from this valve should be no more than a drip and up to 1 litre a day of water dripping.
If this is dripping or running continually, it should be replaced.