Water heaters
Water heater leaking: where it is coming from and what to do
Published by Prime Plumbing · Updated · How we write our guides
Short answer
Shut off the cold water valve above the heater and turn off the gas control or the breaker. Then find where the water is coming from. A leak at the pipe connections, the drain valve or the relief valve can be repaired. Water seeping from the tank body itself means the tank has failed and the heater must be replaced.
How do I shut down a leaking water heater?
- Close the cold water supply valve on the pipe entering the top of the tank
- Gas: turn the control to off or pilot. Electric: switch off the breaker
- If the tank is leaking steadily, attach a hose to the drain valve and empty it to a floor drain or outdoors
Where is the water coming from?
| Location of the water | Likely source | Repairable? |
|---|---|---|
| Top of the tank | Loose supply connection or fitting | Yes |
| Pipe on the side running to the floor | Relief valve discharging | Usually: valve, pressure or temperature issue |
| Drain valve near the bottom | Valve not closed or worn | Yes |
| Under the tank or from a seam | Tank lining has failed | No, replace the heater |
| Outside of a cold tank in humid weather | Condensation | Not a leak |
Why is the relief valve dripping?
The temperature and pressure relief valve opens when the tank is too hot or pressure is too high. Causes include a thermostat set too high, a missing or failed expansion tank, high house water pressure or a worn valve. Never cap or plug it; it is the safety device that stops a tank from rupturing.
Is a leaking water heater dangerous?
A small leak is mostly a water damage risk, but it gets worse. A tank that fails fully releases its whole contents and keeps flowing until the supply is shut off. Water around a gas burner or electrical connections is a hazard, which is why the heater should be shut down first.
When should I call a plumber?
Call whenever you cannot find the source, the relief valve keeps discharging or the tank itself is wet. If the heater is more than 10 years old and leaking from the tank, plan on replacement and ask about the size and type that suits the household.
Common questions
Can I still use a water heater that is leaking?
Not if the tank itself is leaking. If the leak is a loose fitting or the drain valve, it can be used once that is repaired.
How long will a leaking tank last?
There is no safe estimate. A tank that has started to seep can fail completely in days or last a few weeks. Replace it promptly.
Further reading from official sources
- Water Heaters (ENERGY STAR)
This guide is general information for homeowners, not a substitute for an on-site assessment. Plumbing codes and permit rules vary by city and state.