Water Heater Leaking From the Top
When a water heater is leaking water from the top, the source is usually a fitting or valve rather than the tank itself: the cold inlet or hot outlet connection, the T&P valve (temperature and pressure relief valve), the anode rod port, or on an electric heater, the upper element gasket. Those are fixable parts, so a top leak is usually better news than a bottom leak. Find which one is wet, then fix that part.
Find the wet spot
Dry the top of the heater, the pipes and the fittings with a towel. Then watch, or wrap a dry paper towel around each joint and check it a few minutes later. Work through these in order:
- The cold water inlet and hot water outlet, including any flexible connectors and the short nipples that thread into the tank.
- The T&P valve, which sits on the top or high on the side, and its discharge pipe.
- The anode rod, a large hex head on top of the tank on many models.
- On electric models, the upper element cover on the side.
- On gas models, the draft hood and flue at the very top.
- Pipes and fittings above the heater that could be dripping onto it.
Likely causes
Cause 1: Loose or corroded pipe connections
The inlet and outlet see heat cycles every day. Threaded joints loosen, and the fittings that join copper to the steel tank can corrode. Often you'll see white or green crust around the joint. If a compression nut or a flexible connector is weeping, tightening it a quarter turn often stops it. HomeGuide notes that leaks from a fitting may only need tightening. Corroded nipples have to be replaced, which means shutting off and partially draining the tank.
Cause 2: The T&P relief valve
A.O. Smith says a leaking relief valve can be caused by high pressure or thermal expansion. Two things to check:
Water pressure. Screw a pressure gauge onto a hose bib or the heater's drain valve. A.O. Smith recommends 50 to 60 psi and no higher than 80 psi. If yours is higher, the pressure reducing valve needs adjustment or replacement.
Thermal expansion. Water expands as it heats, and in a closed system that expansion has nowhere to go, so the pressure climbs. A.O. Smith's manual says codes require a properly sized, properly pressurized thermal expansion tank in almost all homes. If you have one, its air charge has to match your incoming water pressure.
If pressure is fine and the valve still drips, it has worn out. The A.O. Smith handbook says that in that case the T&P valve must be replaced. Our relief valve leaking page has the details, and expansion tanks covers sizing and charging.
Cause 3: The anode rod port
The anode rod screws into the top of the tank, and its threads can weep, especially after someone has removed and reinstalled it. Re-seal the threads with PTFE tape or pipe dope. If the area around the port is badly rusted, the tank may be corroding there.
Cause 4: The upper element gasket (electric)
A.O. Smith notes that leaks can occur around the heating elements if the gaskets fail. Power off, remove the upper access cover and check for wet insulation. Per the manual, tighten the element until the leak stops, and replace the gasket if it's damaged.
Cause 5: Condensation or a flue problem (gas)
On gas heaters, water around the draft hood can be condensation from the flue, rain coming down a vent without a proper cap, or sweating cold pipes in a humid basement. If drips appear only when the burner first fires on a cold tank, condensation is likely and it should stop as the tank warms. Rust and soot around the draft hood, or water that keeps coming, mean the venting needs a plumber's eye.
Cause 6: Tank failure at the top
Sometimes the tank corrodes through near the top. If water comes from under the jacket or around the top of the tank with no fitting involved, the heater needs replacing. A.O. Smith says a corroded, leaking tank usually means the entire water heater has to go.
Fixes and what they cost
| Repair | Typical cost |
|---|---|
| Leak repair, depending on source | $100 to $1,000 |
| Pressure relief valve replacement | $50 to $300 |
| Expansion tank replacement | $300 to $800 |
| Anode rod replacement by a plumber | $150 to $350 |
| Replacing a leaking tank heater | $600 to $1,800 |
Tightening a connector or re-taping a fitting is a reasonable DIY job. Replacing nipples, relief valves and expansion tanks is straightforward for a plumber and fiddly for a first-timer, because it means draining the tank. Add a service call fee of $50 to $200 in many areas.
When to call a plumber
Call if the relief valve discharges hot water, if your water pressure is over 80 psi, if the leak is from the tank or the venting, or if a fitting is too corroded to turn. Shut the cold supply valve on top in the meantime.
FAQ
Why is my hot water tank leaking from the top?
Common sources are a loose inlet or outlet connection, or the relief valve opening because of high pressure or thermal expansion. An anode port or an upper element gasket can also weep, and sometimes the tank itself is leaking.
Is a water heater leaking from the top dangerous?
The leak itself is usually small, but a relief valve that keeps opening is a warning about pressure or temperature. Check the pressure, and never plug the valve. Water dripping near electrical parts is a shock hazard, so turn the power off.
Can I still use my water heater if it's leaking from the top?
For a slow drip at a fitting, yes, for a short while, but fix it soon. If the relief valve is discharging, turn the heater off and call a plumber.
Sources
- A. O. SmithResidential Electronic Thermostat Electric Water Heater: Installation Instructions and Use & Care Guide (opens in a new tab)
- A. O. Smith / State Water HeatersResidential Hybrid Electric Heat Pump Water Heater Service Handbook (opens in a new tab)
- HomeGuideWater Heater Repair Cost (opens in a new tab)
- A. O. SmithWater Heater Not Working? Troubleshooting Guide (opens in a new tab)