Water Heater Leaking? Causes & Fixes (Step-by-Step)

1. Loose or Corroded Inlet/Outlet Pipe Connections

The cold-water inlet and hot-water outlet connections at the top of the tank can loosen over time or develop corrosion, allowing water to drip down the side of the unit.

1. Turn off the power supply to the water heater (flip the circuit breaker for electric; turn the gas valve to “Pilot” for gas).
2. Shut off the cold-water supply valve above or near the unit.
3. Dry the area thoroughly with a towel, then watch for 10–15 minutes to confirm the drip location.
4. Using a pipe wrench, gently tighten the fittings at the top of the tank—do not overtighten, as this can crack older fittings.
5. If corrosion is visible on the nipples, plan to replace the dielectric nipples to prevent galvanic corrosion.
6. Restore water supply and power; check for continued dripping after 30 minutes.

2. Faulty Temperature and Pressure Relief (T&P) Valve — A Common Water Heater Leaking Cause

The T&P valve is a safety device that releases water if pressure or temperature gets too high. It can drip continuously when it fails or when system pressure is chronically elevated.

1. Locate the T&P valve on the side or top of the tank; it has a metal lever and a discharge pipe running down toward the floor.
2. Check whether the discharge pipe is dripping or wet — this confirms the valve is releasing water.
3. Lift the test lever briefly (have a bucket ready) to flush debris from the valve seat, then release it. If the dripping stops, the valve may be okay but watch it over the next 24 hours.
4. If it continues to drip after flushing, the valve must be replaced. Do not plug or cap the discharge pipe.
5. Shut off water supply and power/gas to the heater. Drain 2–3 gallons from the drain valve to lower tank pressure.
6. Unscrew the old T&P valve with a pipe wrench, wrap the threads of the new valve with plumber’s tape, and thread it in firmly.
7. Restore power and water; test the new valve with the lever after refilling.

3. Leaking Drain Valve

The drain valve near the base of the tank is used for flushing sediment and can develop a slow drip from a worn washer or a loose connection.

1. Locate the drain valve at or near the bottom of the tank.
2. Try hand-tightening the valve cap clockwise — sometimes this alone stops the drip.
3. If the valve body itself is cracked or the drip continues, the valve needs to be replaced.
4. Turn off water supply and power/gas. Attach a garden hose to the drain valve and route it to a floor drain or outdoors.
5. Open a hot-water faucet in the house to break the vacuum, then open the drain valve to empty the tank.
6. Unscrew the old drain valve, wrap new threads with plumber’s tape, and install a replacement brass drain valve.
7. Close the new valve, refill the tank, restore power/gas, and check for leaks.

4. Sediment Buildup Causing Overheating and Pressure Spikes

Mineral sediment accumulates on the bottom of the tank over time, forcing the unit to overheat and causing the T&P valve to release water as a pressure-relief response.

1. Listen for a rumbling or popping noise from the tank — this is a classic sign of heavy sediment buildup.
2. Flush the tank annually: attach a hose to the drain valve, shut off the cold supply, open a hot faucet in the house, then open the drain valve until water runs clear.
3. Check and lower the thermostat setting if it is above 120°F (49°C), as excessive heat accelerates sediment hardening and pressure issues. For guidance on safe temperature settings, see the U.S. Department of Energy’s water heating guidelines.
4. If flushing is no longer effective and sediment is cemented, the tank may need full replacement.

5. Anode Rod Deterioration Leading to Inner Tank Corrosion

The sacrificial anode rod protects the tank lining from rust; when it is fully depleted, the steel tank itself begins to corrode and can develop pinhole leaks.

1. Shut off water supply and power/gas. Relieve pressure by opening a hot-water faucet.
2. Locate the anode rod port on top of the tank (it may be under a sheet-metal cover or integrated into the hot-water outlet).
3. Use a 1-1/16 inch socket and breaker bar to unscrew the anode rod — it may be very tight.
4. Inspect the rod: if it is less than ½ inch in diameter or heavily coated in calcium, replace it immediately.
5. Wrap threads of the new rod with plumber’s tape, insert it, and tighten firmly.
6. Restore water and power; inspect all seams and welds on the tank exterior for rust stains after refilling.

6. Cracked or Corroded Tank Body

When rust penetrates the inner lining of the tank, water seeps through the shell and pools underneath the unit — this damage is irreversible and requires full tank replacement.

1. Dry the area around the base of the tank and place paper towels under all sides to pinpoint the leak source.
2. Check that the leak is not coming from a valve or fitting above — water can run down the tank wall and appear to originate from the bottom.
3. If the water is visibly rusty or the tank shell has visible rust spots or bulging, the tank is failing.
4. Turn off the water supply and power/gas immediately to prevent further hazard.
5. Contact a licensed plumber to drain and replace the unit. Most storage water heaters have a lifespan of 8–12 years; check the serial number to determine age.

Frequently asked questions