Water Heater Leaking From the Bottom: Causes and What to Do

Finding water under your water heater is stressful, especially when the unit sits in a garage or closet where damage spreads quietly. The source of the leak decides whether you need a small repair or a new tank.

The Short Answer

A leak from the bottom of the tank usually means one of three things: a loose or failing fitting, a bad drain valve or temperature and pressure relief valve, or a corroded tank. Fittings and valves can often be repaired. A tank that is leaking through its shell cannot be fixed and needs replacement.

What to Do Right Away

1. Turn off power to an electric unit at the breaker, or set a gas unit to pilot or off.
2. Close the cold water supply valve on top of the heater.
3. Place a bucket or towels, and keep the area clear.
4. Take photos for insurance, then call a professional.

Common Causes

Loose or worn fittings

Supply lines and connections on top can drip down the tank and look like a bottom leak. Tightening or replacing them is a small job.

Drain valve

The valve near the bottom can weep when it is worn or has sediment in it.

Relief valve

A valve that drips can mean excess pressure or temperature, which is a safety issue, not just a nuisance.

Tank corrosion

Mineral buildup and an exhausted anode rod let rust eat through the steel. Arizona's hard water speeds this up. This is the leak that means replacement.

Repair or Replace

If the leak is at a fitting or valve and the tank is under about ten years old, repair is often reasonable. If water is coming from the tank body or the unit is old, replacement is safer and cheaper in the long run. See our guide on repair or replace and our water heater leaking service.

Prevent the Next Leak

Flush the tank on a schedule, check the anode rod, and replace an aging heater before it fails. Our replacement cost guide explains what to budget.