Hot water system is leaking

What to do, in order

1. A little water from the relief valve drain while the tank heats is normal. More than a bucketful in 24 hours means something is wrong.
2. Never block or cap the relief valve or its drain pipe.
3. Hot water pouring from the relief valve until the tank runs cold? Turn the heater off - electric: the water heater switch on the switchboard; gas: the gas control knob on the heater - and book an inspection.
4. Tank or pipes leaking? Turn the heater off the same way, then close the cold water isolation valve on the pipe going into the heater.
5. Can't find or close that valve? Turn the whole house off at the stop tap next to the water meter.
6. Don't try to repair it yourself - servicing must be done by a qualified person.

When you need a plumber

Call a licensed plumber (or the manufacturer's service line) if the relief valve discharges more than a bucketful a day or runs steadily, the tank or its fittings leak, or there's no hot water. A steady flow, often at night, can mean mains pressure is rising too high - a plumber can fit a pressure limiting valve. Renting? No hot water, or an appliance wasting a lot of water, is a legally urgent repair: call your rental provider or agent on the emergency number you were given and confirm it in writing.