Leaking From the Top? The 5 Fittings That Usually Cause It, and the One Leak That Doesn't Get Fixed
A water heater leaking from the top is usually good news, as leaks go. Almost everything up there threads or bolts on, which means it can be taken off and replaced. The exception is the tank's own top seam.
Turn the heater off and close the cold supply first. Then dry the top of the tank completely and watch which joint wets first.
1. The flexible water connectors
Braided or corrugated connectors join the house pipes to the hot outlet and cold inlet. Their nuts loosen and their seals age. A connector that is wet at the nut is replaced, not tightened forever.
2. The nipples and dielectric fittings
The short nipples threaded into the tank often carry a dielectric lining or union, because steel tank and copper pipe corrode each other where they meet. That corrosion shows as white and green crust. When a nipple weeps under that crust, it is replaced along with its connector.
3. The cold shut-off valve above the heater
The valve on the cold line above the tank can drip from its stem, which looks like a leak from the top of the heater. Snugging the packing nut a quarter turn often stops it. If it is seized or keeps dripping, the valve itself is replaced.
4. The relief valve threads
On some tanks the temperature and pressure relief valve sits on top. Water at its threads, rather than out of its pipe, needs a closer look: a new valve fixes worn threads on the valve, but water from inside the tank's threaded opening means the steel around it is failing.
5. The anode rod port
The anode rod screws into the top of the tank, sometimes under a plastic cap. Its threads can seep. Re-sealing or replacing the rod usually ends it, and checking the rod tells you a lot about how much life the tank has left.
The leak that doesn't get fixed: the top seam
If every fitting is dry and water is coming from the seam where the top of the tank meets the body, or from the threads of the tank itself, the steel has corroded through. That tank is replaced. The repair-or-replace questions help you plan the next step.
Is a water heater leaking from the top dangerous?
A drip at a fitting is not dangerous in itself, but water running over a gas heater's controls or an electric heater's wiring is a reason to turn the heater off now. Most top leaks are repaired for an estimated $150 to $400; the full cost breakdown has the other common fixes. To have the fitting traced and replaced, see water heater leak repair near you.
Quick answers
Why is my water heater leaking from the top seam?
The steel tank has corroded through at the seam. Unlike a fitting, that cannot be repaired, and the heater is replaced.
My cold water supply valve is leaking. What can I do?
Try snugging the packing nut under the handle a quarter turn. If it keeps dripping or will not turn, the valve is replaced.
Can a leak on top of a water heater be repaired?
Usually. Connectors, nipples, valves and the anode rod port are all replaceable. Only the tank's own seam is not.
Leak still running?
A plumber who handles leaking water heaters can trace it and quote it in writing.
