Water Heater Leaking From the Bottom

What to do right now

1. Turn off the energy. Electric heater: switch off its breaker. Gas heater: turn the gas control knob to "Off" or "Pilot".
2. Shut off the cold water supply. It is the valve on the cold pipe going into the top of the tank. Turn it clockwise. Not sure where it is? Use our guide to find your main water shut-off valve.
3. Protect the area. Move boxes and rugs, mop up, and put a pan or towels under the heater.
4. Find where the water comes from using the diagram below, then decide: small fix or call now.

Where is the water coming from?

What you see	Likely cause	Fix or replace?
Water on top of the tank or running down the side	Loose or corroded pipe fitting on top	Usually fixable
Water coming out of the pipe on the side of the tank	Relief valve opening from high pressure or heat, or a worn valve	Fix soon, check pressure
Drips from the faucet-like valve near the bottom	Drain valve not fully closed or worn out	Usually fixable
Small puddle under a gas heater that dries up	Condensation when the tank is full of cold water	Often normal
Water from under the tank, rust, a wet base that never dries	Tank rusted through inside	Replace the heater

How to find the source

Dry everything off with towels: the floor, the drain valve, the relief valve pipe and the fittings on top. Then wipe each spot with a dry paper towel every few minutes and see which one gets wet first. Water runs down, so a leak that looks like it comes from the bottom often starts higher up. Look closely at the top fittings and the relief valve before you decide the tank is gone.

The causes, one by one

1. Leaking drain valve

The drain valve near the bottom is used to flush the tank. It can drip if it was not closed all the way or if the washer inside wears out. Try closing it by hand, gently. If it still drips, the valve can be replaced, and it is one of the cheaper water heater repairs.

2. Relief valve letting out water

The temperature and pressure relief valve is a safety part on the side or top of the tank, with a pipe running down toward the floor. Water from that pipe means the valve opened because the water got too hot, the pressure got too high, or the valve itself is worn. Do not plug it or cap the pipe. Have it checked, because the cause can be a bad thermostat or high water pressure in the house.

3. Condensation on a gas water heater

When a gas burner heats a tank full of cold water, moisture can form and drip down under the heater. It is common after heavy hot water use and on cold days. A small amount that dries up once the tank is hot is normal. Water that keeps coming is a leak.

4. A leak higher up

Fittings where the hot and cold pipes connect on top can loosen or corrode. The water runs down the side, under the jacket, and shows up at the bottom. These are usually easy to fix.

5. The tank itself is leaking

Over the years, sediment and rust eat through the steel inside the tank. Once the tank leaks, it cannot be patched. The only fix is a new water heater. The U.S. Department of Energy puts the life of a tank water heater at about 10 to 15 years, so an older tank with water under it has usually reached the end.

Repair or replace?

• Repair: leaking drain valve, loose fittings on top, a worn relief valve, a bad thermostat.
• Replace: water from the tank body, rust at the base, a tank over 10 years old with repeat problems.
• Think about tankless: if you are replacing anyway, a tankless heater saves space and never runs out of hot water. Our tankless water heater service covers repairs and new installs.

Not sure which one you have? Our water heater repair service finds the source, tells you what we found and what the fix is, then does the repair or the replacement. If water has soaked into the floor or a wall, our leak detection service checks for hidden damage.

How to prevent the next leak

• Flush a few gallons from the drain valve once a year to clear sediment. Fall is a good time. See our fall plumbing checklist.
• Set the heater to about 120°F, the setting the Department of Energy suggests for most homes.
• Put a drain pan under the heater, piped to a floor drain if you can.
• Add a cheap water leak alarm on the floor next to the tank.
• Have the anode rod checked every few years. It is the part that slows rust inside the tank.