Water Heater Leaking From the Bottom — Find the Source and Fix It

A puddle under a water heater comes from one of three places: the temperature and pressure relief valve discharge pipe, the drain valve, or a corroded tank. The first two are fixable; a corroded tank requires full replacement. Identifying the leak source takes only a few minutes.

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   Step 1: Dry the area and identify the leak source

   Wipe the floor and the base of the unit dry. Look for the water trickling or dripping by running your hand along the tank exterior, pipes, drain valve, and discharge pipe from the T&P relief valve. Do this while the tank is full and under pressure. Tracing the leak to its source before doing anything else saves time and prevents misdiagnosis.

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   Step 2: Check the drain valve

   The drain valve is at the bottom of the tank, usually plastic, and looks like a hose bib or garden spigot. A slow drip here usually means the valve is not fully closed (turn clockwise firmly) or the rubber seat is worn. A leaking drain valve can be temporarily fixed by threading a garden hose cap onto the outlet, or replaced permanently with a new valve after draining the tank.

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   Step 3: Check the T&P relief valve discharge pipe

   The temperature and pressure relief valve (T&P valve) is a safety device on the side or top of the tank. It has a copper or CPVC pipe running from it down to near the floor — the discharge pipe. If water is dripping from this pipe, either the valve is doing its job (the water pressure or temperature is too high) or the valve has failed and is weeping. A weeping T&P valve should be replaced.

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   Step 4: Inspect the tank body for corrosion

   If the leak is coming from the tank itself (rust streaks, mineral buildup, or moisture on the tank body below the water line), the tank has corroded through from the inside. This is not repairable — the water heater must be replaced. A corroding tank will worsen rapidly once it begins leaking through the steel shell.