Why Does My Water Heater Keep Leaking?


Five Reasons Why a Water Heater Can Leak


Here are five things to look for when diagnosing the source of a leak and determining the proper fix.


  1. Leaking at the Water Supply Lines


The first place to search is above the water heater, the plumbing pipes. Leakage from the top of the water heater will quickly leak down and even work its way down the insulation to make it look like the leak comes from the tank itself.


If required, test the plumbing pipes above the water heater, using a stepladder. Pay particular attention to the water supply lines that go into the boiler. These may be rigid connections to the pipes or flexible supply tubes. The most common cause of leaks above the water heater is flexible water supply tubes, as it is common for these tubes to fail well before the water heater is ready for replacement. If the supply tubes are insulated, remove it so that the tubes can be checked and replaced where appropriate.


To remove the flex lines of the water heater, the water was turned off at the water heater first. This will be a shut-off valve on the cold water pipe which will connect to the water heater. When replacing the water supply tubes, check that the water is turned off by turning somewhere in the house to the hot side of a faucet to see if the water is still running. If the heating has been turned off successfully, no water will flow out of the heater.


   2. Leaking at the Water Heater Nipples


Another commonplace to find leaks is the water heater nipples on top of the water heater, which links the water heater to the cold water inlet pipe and the hot water exit pipe. The threads are the thinnest component on the nipple and finding holes in them is not uncommon. This can be difficult to distinguish from a leak at a supply tube, but if you have already adjusted the supply tube and are still finding leaking water, the nipple is a likely cause.


It can be quite difficult to remove the water heater nipples and will take a pipe wrench and some leverage. Before doing this repair make sure to turn off the water and check that it is off.


    3. Leaking at the Temperature and Pressure Relief (T & P) Valve


Temperature and pressure (T&P) valve is another potential location for leaks. A T & P valve leak is a more serious situation and you're going to want to take the time and find out the source. Normally, a T-and-P valve will not start dripping or leaking, unless a problem arises. Different possible triggers:


  • If the valve has recently been replaced, it is now likely that it fails to close properly. The problem can be solved by tightening the handle or reinstalling it with fresh plumber tape wrapped in the threads.

  • If the water heater heats the water too much, the T & P valve o leak may be caused by excessive pressure. If you do not already have one in your plumbing system, the alternative might be to lower the water temperature or to add a water expansion tank.

  • The leaking T & P valve may indicate the overall water pressure in your home is too high, and that the pressure regulator is not working properly. 

  • If the house's water pressure is low and the water heater heats normally, then you may have a defective T & P valve that needs repair. Make sure that the water is turned off before removing the valve, and that there is no pressure in the tank. By opening the lever on the T & P pump, or by opening a hot water faucet somewhere in the building, you can relieve pressure.


If you believe there is still a problem or are unable to get to the bottom of the issue, call a professional plumber to help assess and remedy the situation.


    4. Leaking at the Drain Line


Another common problem is a leak in the drain valve at the bottom of the water heater. It is normal for the drain valve to fail to close completely after draining or flushing of a water heater. You can cap this drain valve with a hose cover, or you can completely replace the drain valve with a new valve. Until removing and replacing this valve you will need to turn off the hot water and drain down the water heater.


     5. Leak in the Tank


Eventually, if none of the previous checks indicated a reason for leakage, then the tank inside the water heater is likely to have gone wrong. This will usually be a big, flooding leak, not a little trickle. If the tank has split and leaks, the water heater can not be patched, and it has to be replaced.

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