If the tank is leaking steadily, shut off the cold-water valve above the heater and turn off its gas or power. Hot water and pressure can scald, so keep clear of the relief valve outlet.
Find the source
- Cold or hot connections at the top: a loose fitting or failing supply line, often repairable
- The temperature and pressure relief valve or its discharge pipe: the valve may be failing, or the heater may be overheating or overpressured
- The drain valve near the bottom: a worn or partly open valve
- The tank body or water pooling from underneath with no other source: the tank has corroded through
What to do now
Close the cold-water supply valve on top of the heater. Turn a gas heater’s control to off, or switch off the breaker for an electric one. Put a pan or towels down and keep the area clear.
When a leak means replacement
A tank that leaks from its body cannot be repaired. Leaks from valves and fittings usually can. A heater that is older and showing rust around its base is at the end of its life either way.
A relief valve that discharges
Water from the relief valve is a safety device doing its job. It can mean the valve is worn, but it can also mean the temperature or pressure is too high, which needs to be diagnosed rather than capped.