First ten minutes
- Rule out gas.If you smell gas at any point, leave the house and call 911 or SoCalGas from outside. Water can wait.
- Close the cold supply.Turn the valve on the cold pipe entering the top of the heater. If it is stuck or the leak is heavy, shut the water off at the main for the house.
- Turn the heater off.Set a gas control to Off or Pilot, or switch off the breaker for an electric heater. A tank should not heat without water coming in.
- Protect the area.Move stored boxes, keep children and pets away, and use towels or a shallow pan. Water near the base of a tank can be hot.
- Find the source.With a flashlight and a dry paper towel, work from the top of the heater down to see where the water first appears.
Where the water is coming from
| Location | Likely source | Typical outcome |
|---|---|---|
| Top of the heater, at the pipes | Supply connectors, nipples or a loose fitting | Often repairable |
| Relief-valve discharge pipe | Relief valve opening or worn | Needs a check of pressure, temperature and the valve |
| Drain valve near the bottom | Worn or not fully closed drain valve | Often repairable |
| Under the jacket or from the base | Inner tank corroded through | Replacement |
| Puddle with no drip on the heater | Condensation, or another pipe nearby | Check other lines before blaming the heater |
Why a leaking tank cannot be fixed
The tank inside the jacket is steel lined with glass, protected by a sacrificial anode rod. Once the anode is used up, the steel starts to corrode, and a pinhole becomes a seep that grows. There is no patch that lasts, because the metal around the hole is in the same condition.
That is why a plumber will usually tell you that water coming from the base or from under the insulation means the heater is finished. A leak at a fitting is a different story: the tank may have years left, and replacing a connector or drain valve is ordinary repair work.
Before the plumber arrives
- Take photos of the wet area and the highest point you found water
- Write down the model number and manufacture date from the rating plate
- Note whether the heater is gas or electric, tank or tankless
- Clear a path to the heater and the shutoffs
- Leave the heater off until it has been looked at
An example: water around a closet tank
Illustrative example. Not a real job or customer.
A homeowner finds water on the hall carpet next to the closet that holds the water heater. The top fittings are dry, but the base of the jacket is wet all the way around.
- They close the cold supply above the heater and switch the gas control to Off
- They pull back the carpet edge and set fans to dry the area
- A licensed plumber confirms the water is coming from inside the jacket
- They compare written prices for like-for-like replacement and any code updates
The tank had corroded through, so replacement was the only sensible choice. Shutting off the water early kept the damage to the closet floor.
Common questions
- Can I keep using a water heater with a small leak?
- If the leak is from the tank body, no; it only gets worse and can fail suddenly. If it is a dripping fitting, shut the supply until it is repaired rather than living with it.
- Should I drain the tank myself?
- Draining can reduce how much water could escape, but tank water may be scalding and old drain valves can break. If you are unsure, close the supply and wait for the plumber.
- Is a wet relief-valve pipe a leak?
- It means the relief valve has opened or is worn. Never cap the pipe. Have a plumber check the valve, the water pressure and the temperature setting.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.