Water Heater Leaking From Top: Causes & Fixes

Cause 1: Loose or corroded pipe fittings (easiest fix)

The cold-water inlet and hot-water outlet pipes connect to the top of the tank with threaded fittings that can vibrate loose or corrode over time, allowing water to drip down the side of the unit.

1. Turn off the power to the water heater at the breaker (electric) or set the gas valve to “Pilot” (gas).
2. Shut off the cold-water supply valve located above or near the top of the heater.
3. Dry the area around all top fittings with a towel so you can see exactly where water is originating.
4. Using a pipe wrench, attempt to tighten each fitting by turning clockwise one-quarter to one-half turn. Do not over-tighten.
5. Restore water supply and power, then monitor for 30 minutes. If the fitting still drips, shut everything off again.
6. Wrap the threaded connection with fresh plumber’s tape (PTFE tape), reattach the fitting, and re-test.

Cause 2: Faulty temperature and pressure (T&P) relief valve

The T&P relief valve is a critical safety device mounted on the top or upper side of the tank. A worn or corroded valve may weep or discharge water when system pressure is normal, indicating it needs replacement.

1. Locate the T&P relief valve — it has a small lever and a discharge pipe running down toward the floor.
2. Place a bucket under the discharge pipe, then briefly lift the test lever to flush any debris. Release it. If water continues to flow freely after release, the valve is faulty.
3. If you need to replace it, shut off the cold-water supply and power/gas. Open a hot-water faucet in the house to relieve pressure.
4. Drain a few gallons from the tank via the drain valve to drop the water level below the valve port.
5. Unscrew the discharge pipe, then use a pipe wrench to remove the old T&P valve.
6. Wrap the threads of the new valve with plumber’s tape and thread it in by hand, then tighten with a wrench. Do not over-tighten.
7. Reattach the discharge pipe, restore water supply and power, and check for leaks.

Cause 3: Deteriorated anode rod or anode rod port

The anode rod is threaded into a port on top of the tank and is designed to sacrificially corrode to protect the tank. Once the rod is depleted, the port’s threads can corrode and allow water to seep out.

1. Locate the anode rod port on top of the tank — it may be hidden under a sheet-metal cap or plastic cover.
2. Shut off the cold-water supply and power/gas. Drain several gallons from the tank to lower pressure.
3. Use a 1-1/16-inch socket with a breaker bar or impact wrench to break the anode rod loose — it is often very tight.
4. Inspect the threads on both the rod and the port. If the port threads are damaged, contact a licensed plumber; repairing stripped tank threads is a professional job.
5. If threads are intact, wrap the new anode rod’s threads generously with plumber’s tape and thread it in by hand, then torque it snug with the socket wrench.
6. Restore water and power, then inspect the port for drips after refilling.

Cause 4: Leaking water inlet or outlet nipple

Dielectric nipples (also called heat trap nipples) are installed at the water connections on top of the tank to prevent galvanic corrosion between the steel tank and copper pipes. These plastic-lined fittings can crack or corrode, causing drips.

1. Shut off the cold-water supply and power/gas. Open a hot-water tap in the home to relieve pressure.
2. Use channel-lock pliers or a pipe wrench to disconnect the supply and outlet pipes from the nipples.
3. Unscrew the old nipples from the tank ports with a pipe wrench, turning counter-clockwise.
4. Inspect the tank port threads for corrosion damage. If threads look sound, proceed.
5. Wrap new dielectric nipple threads with plumber’s tape and thread them into the tank ports by hand, then snug with a wrench.
6. Reconnect supply and outlet pipes, restore water and power, and check for leaks.

Cause 5: Loose or failed expansion tank connection

Many closed plumbing systems require a thermal expansion tank, which is typically tee’d into the cold-water supply line directly above or near the water heater. A loose or corroded connection where the expansion tank meets the supply line can drip water onto the top of the heater and appear to be a tank leak.

1. Inspect the expansion tank’s connecting fitting and the tee joint above the water heater for moisture or mineral deposits.
2. Dry the area and watch carefully for 10–15 minutes to confirm this is the leak source.
3. Shut off the cold-water supply and power/gas.
4. Try tightening the union or fitting connecting the expansion tank one-quarter turn with a wrench.
5. If the fitting is corroded or cracked, it must be replaced. Shut off and drain the system before removing the old fitting.
6. Apply plumber’s tape to the new fitting threads and reinstall, then restore water and power and recheck.

Cause 6: Internal tank corrosion (water heater leaking from top seam)

If water appears to be seeping from the top seam of the tank body itself — not from any fitting or valve — the inner lining has likely failed and the tank is corroding from the inside out. This is not repairable and the unit must be replaced.

1. Dry all exterior fittings and valves thoroughly and rule them out as the leak source before concluding the tank itself is leaking.
2. Look for rust-colored water, a persistent wet ring around the top seam, or visible corrosion on the tank body.
3. If you confirm the tank body is the source, shut off the cold-water supply and turn the heater off immediately to prevent further damage.
4. Do not attempt to patch a leaking water heater tank — internal pressure makes patches dangerous and ineffective.
5. Contact a licensed plumber to remove the old unit and install a new water heater. Check the Energy Guide label and consider upgrading to a more efficient model.
6. For guidance on choosing an energy-efficient replacement, see the U.S. Department of Energy Water Heating guide.

Frequently asked questions