Under normal circumstances, with a leak at the top of your water heater, there are only a few causes of the leak, and the solutions may be simpler than you thought.
See also: Water heater leaking from the BOTTOM
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Leaking from the Top of the Tank: Finding the Source
If you suspect that you have a leak from the top, turn off the power to your water heater. Most homes have a dedicated circuit breaker for an electric water heater, and some were built with an easily accessible secondary shut off in the vicinity of the heater itself. For a gas water heater, turn the thermostat control to the off position.
Do not turn off the cold water inlet until the leak has been found, as the leak could stop without sufficient pressure. If you cannot see a leak, slowly run your dry hand over the various pipes and fittings. If you are still unsuccessful in locating the leak, try wrapping the pipes and joints with tissue paper, being careful to watch for damp spots.
Most Common Causes of Water Heater Leaking from the Top
Many water heaters have a ball valve, an in-line valve to turn off the water flow, identifiable as a joint with a handle. When the handle is parallel to the pipe, the valve is open and water is flowing. If the handle juts off at a right angle, the valve if closed.
If the handle or valve is dripping, you can simply tighten the nut which holds the handle in place. If the leak gets worse, you may have to replace the valve. If the leak is not affected, look for another cause.
Leaking Pressure Relief Valve
The temperature and pressure relief valve (T&P valve) is located on top of your water heater, and acts as a safety valve to release excessive pressure or water in case of overpressurization or thermostat failure.
This valve is typically located at top center of the tank. If this valve is leaking, it is usually better to replace it completely. Replacing the valve is relatively simple and can be done in only a few minutes minutes.
If the valve is not the source of the leak, the most likely problem is a loose connection or even a stripped threaded nipple. If the tank uses copper tubing instead of threaded pipe, you may need to enlist the services of a professional plumber unless you are comfortable with making the repairs yourself.
Another option is to re-plumb the tank using threaded pipe or water-rated PVC to simplify any future repairs. Turn off the water and drain the tank before disconnecting any pipes.
If there isn’t a compression coupling available, you will need to cut the leaking pipe in an area that can be spliced back together. If the leak is at a location where PVC or CPVC is joined to metal, such as entering the top of the heater, tighten the threaded fitting with a pipe wrench or appropriate tool.
Reconnect the pipe using a female to female coupling. Allow the PVC cement to fully dry before turning on the water, and do not turn on the power until the water has been turned on to prevent possible damage and the need to replace your water heater element.
In order to tighten threaded pipe, you will have to located and disconnect the compression coupling, a special female-female fitting that slides over two pipe ends, joining them together using washers inside special nuts on the coupling.
When the compression coupling has been disconnected, tighten the offending joint with the appropriate wrench and then reconnect the compression coupling.
Water Heater Repair Notes
Tightening a loose connection may not stop the water heater leak by itself. For more dependable results, completely disconnect the suspect joint and wrap the threads using Teflon tape or joint compound and then install them as described above.
In some rare situations, the problem may be caused by a faulty nipple, a short piece of threaded pipe used to connect other pipes to the water heater or a valve. Nipples can be purchased in precut lengths from your local hardware store. For better, long lasting results, replace nipples with a dielectric nipple, recognized by the hard plastic lining inside the nipple.
When tightening joints and connectors, take care to avoid over torquing. A good rule of thumb is to tighten a pipe finger-tight, and then use a wrench to tighten it 1/4 turn at a time until is firmly in place. Over Torquing can cause the threads to strip, turning a minor problem into a serious leak and resulting in additional repairs.