Why is my water heater leaking from the bottom?

By Dana Whitlock. Updated October 2026. Repair or replace?

Water at the base of a tank heater has four common sources: condensation, a dripping drain valve, discharge from the relief valve pipe, or the steel tank itself rusting through. The first three are often fixable. A leaking tank is not, and it will only get worse. Your job is to figure out which one you have by looking, then limit the water damage.

Likely causes

Condensation on a cold tank Safe to check

When a gas heater fills with cold water, moisture from the burner exhaust can condense and drip onto the burner area. A. O. Smith's manual notes this is not a leak and stops once the tank reaches operating temperature. If the puddle dries up after an hour or two of heating, this was likely the cause.

A dripping drain valve Safe to check

The drain valve near the bottom of the tank can seep at its stem or spout, especially after someone flushes the tank. A slow drip from the spout is visible at a glance.

Relief valve discharge running down Safe to check

The temperature and pressure relief valve near the top has a discharge pipe that runs down the side and ends near the floor. Water from that pipe means the valve opened. Treat it as a pressure or temperature warning rather than a plumbing leak.

Corroded tank Pro job

Once the anode rod is spent, the glass-lined steel tank begins to rust from inside. Rheem calls pooling water around the tank body a serious concern and says replacement is the only safe, cost-effective fix. There is no patch for a tank leak.

Leaking connections above Safe to check

Water can start at a fitting on top and run down the jacket, showing up at the base. Look for drips or mineral crust on the pipes above the heater.

Safe things to check first

• Dry the floor and the base, then watch for 30 minutes to see where fresh water appears.
• Look at the end of the relief valve discharge pipe. Wet or dripping means the valve opened.
• Check the drain valve spout and stem with a dry paper towel.
• Inspect fittings and pipes on top of the heater for drips or crusty white or green deposits.
• If water is pooling and you cannot stop it, close the cold water supply valve on the pipe feeding the heater, and turn off the breaker (electric) to protect empty elements. On gas units, leave the gas control alone and let the plumber handle it.

When to stop and call

Call a licensed plumber the same day if the water comes from the tank body, if the relief valve discharges more than a few drops, or if you cannot find the source. A corroded tank can fail suddenly and release its full volume. If the relief valve is releasing large amounts of very hot water, A. O. Smith tells owners to shut off the supply and call a qualified person. Smell gas anywhere near the heater? Leave and call the gas utility from outside.

Repair or replace?

Start with its age. Type the serial from the label:

A drain valve or fitting repair is cheap and worth doing on almost any heater. A leaking tank ends the conversation. It needs replacing whatever its age. For leaks you cannot pin down, date the heater with the age decoder above. DOE's average life for a gas tank is about 14.5 years, and inspector charts put a conventional heater at 6 to 12 years. Past that range, plan on replacement and use the cost range above and the quote checker to keep the bid honest.