Water Heater Leaking from the Top: Everything You Should Know

    Water Heater Leaking on Top

    Frequently, when a water heater leaks from the top it's a fixable problem. It's also a less expensive problem. However, if the leak isn't  promptly repaired it could lead to a serious issue, especially if the water finds it's way into the electrical compartment.

    If the leak goes undetected, you could be dealing with serious and costly water damage to nearby floors and/or walls. To put it simply, when your water heater is leaking from the top, dealing with the leak quickly is not optional, it's a necessity.

    Locate the Water Heater Leak


    Safety First

    • Electric Water Heater - Locate the circuit breaker on your electrical panel and switch it OFF.
    • Gas Water Heater - Turn the thermostat control knob to OFF.
    • Do NOT turn off the incoming water until you locate the leak. This may seem counter-intuitive, but turning off the water will make it difficult to determine the location of the leak.

    The steps below will help you determine the location of the leak. In most cases, when a water heater is leaking from the top, it's usually pretty easy to pinpoint to leak.

    • Find the cold-water inlet valve. It's on the cold water pipe which supplies water to the water heater. The valve is usually a lever or a knob type valve. (Some water heaters don't have this valve installed, if this is your situation, you'll need to shut off the water to the entire house). Do NOT turn the water off at this time.
    • With the power shut OFF and the cold-water inlet valve still ON, use a towel to dry the top of the water heater.
    • Then place a paper towel along the top of the heater to help identify the leak. 
    • Check the seals and pipes leading to the water heater for drippage.
    • Once you locate the leak, turn OFF the cold-water inlet valve to prevent further water damage.

    Causes and Fixes When Your Water Heater Leaks from the Top

    Cold-Water Inlet Valve

    The Cause

    The cold water inlet valve allows the flow of cold water into the heater. Turning it off will stop the water from entering the tank when you need to carry out maintenance, repairs, or to drain the tank in preparation for a replacement.

    Frequently, the  cold-water inlet valve sits directly above the heater. If this is the case, and the valve is leaking, you may notice water dripping onto the top of your water heater.

    The Fix

    If your water inlet valve is leaking you can first try to tighten the valve. There should a nut that connects the handle to the valve, take a screw driver and tighten the nut. 

    If tightening the valve didn't solve the leaking problem, you might have a defective valve which will need to be replaced. 

    Cold Water Inlet Valve Recommendations

    Pipe Fittings or Connections

    The Cause

    Check all the fittings and connection points along the inlet and outlet pipes. As time passes, the fittings sometimes become slightly loose or corroded which could result in leaks.

    Corroded fittings typically have the appearance of a whitish powder substance or a build-up of rust.

    The Fix

    If you find a loose pipe connection, you should be able to stop the leak by tightening it with a wrench. However, if the fitting is corroded, then you'll need to replace the fitting.

    Replacing the fitting should be a relatively easy task unless it's difficult to remove, or copper tubing was used instead of threaded pipe.

    You may find the leak is above the fitting. If that's the case you may need to replace the dielectric union.

    How to Replace a Supply Line

    If you notice the dielectric nipples are corroded it's probably a good idea to replace the fittings. Keep in mind that the problem may actually be with the tank itself, which is far more serious and may require purchasing a new water heater.

    Although removing the dielectric nipples from the tank can sometimes be difficult, replacing them is typically inexpensive and easy.

    How to Replace Dielectric Nipples

    T&P Relief Valve

    The Cause

    The T&P relief valve is a safety valve designed to keep your tank from building up too much pressure. It is also known as the Temperature and Pressure Relief Valve. 

    The valve is typically located on the side of the tank, however sometimes it's on the top. When looking for a leak, check the following:

    • The base where the valve connect to the water heater.
    • The pipe attached to the valve.

    The Fix

    Leak from the Base

    If the leak is orginating from the base of the T&P valve you should first open the valve and allow it to flush away any debris (be careful, the water will be hot). If after flushing, it is still leaking, you should replace the valve. 

    How to Replace a T&P Relief Valve
    • Check that the water heater's power and water are turned OFF.
    • Allow the water to cool, then drain the tank to a level that is lower than the T&P valve.
    • Open a nearby hot water tap to allow the air to flow into the tank.
    • Once the water within the tank is below the T&P valve, unscrew the valve using a pair of channel locks.
    • Inspect the opening of the tank where the valve was located. Look for signs of rust or corrosion.
    • If you find evidence of rust or corrosion, then you'll need to replace your water heater.
    • If you did not find rust or corrosion wrap Teflon tape around the threads of the new T&P valve. Then screw the valve back into the tank.
    • Do NOT power up your water heater unless the tank is completely full of water. Failure to do so will result in damage to the heating elements.

    Watch The Video

    Leak from the Pipe

    If the drain pipe is the source of the leak, then your T&P valve is most likely not faulty. Instead, it's a sign that the pressure within your water heater is at a point where the T&P valve is triggered to open for safety.

    Verify that the power and water are off. You may want to consider contacting a professional plumber to assess the situation. Click HERE to read our extended article on the T&P Relief Valve.

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    Anode Rod Port

    The Cause

    Water heater tanks are made of steel, and steel rusts. An anode rod is a long, thin, solid pipe that's designed to sacrifice itself in order to protect the tank. The rod should be checked as part of a maintenance routine, to ensure that it is still healthy enough to perform its job.

    If the anode rod is not replaced after it has "sacrificed itself" to protect the water heater,  the water within the tank can leak through the port.

    The Fix

    The anode rod is very important to the heath of your water heater. It can have a major influence on the service life of the heater. Any issues should be dealt with quickly.

    In most cases, replacing the anode rod will fix the situation, but if the corrosion has been undetected over an extended period of time, its possible that the water heater will need to be replaced.

    Contacting a professional plumber to assess the situation may be your best course of action.

    How to Replace an Anode Rod

    Expansion Tank

    The Cause

    An expansion tank is a small tank that is typically located on or above the top of the water heater. Not all water heaters have an expansion tank, but if yours does, it's function is similar to that of the T&P relief valve.

    This secondary safety device is designed to absorb excess hot water. When water is heated, it expands, and if left unchecked, the pressure within the tank can become too high. The high pressure could damage valves, joints, and even the water heater.

    An expansion tank is designed to prevent damage from happening by taking in heated water to ensure that the water pressure in the heater does not increase significantly. There are 3 areas where and expansion tank leak could occur:

    • The threaded connection.
    • The air valve positioned opposite the threaded connection. (There should never be water coming from this valve)
    • The tank itself.

    The Fix

    If the leak is coming from the threaded connection:

    • Remove the expansion tank from the connection point.
    • Apply thread sealer to the threads.
    • Tighten the expansion tank firmly back in place.

    If the leak is coming from the air valve or the tank itself, then you need to replace the expansion tank. You may want to consider contacting a professional plumber since a pressure adjustment will be necessary after the expansion tank is replaced.

    How to Replace an Expansion Tank

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    What Else Could Cause the Leak?

    Fortunately (and to your relief), sometimes when your water heater is leaking from the top it may not be because of a malfunctioning or defective part. Here are a few other possible causes:

    • Rain water - When rain water travels down the flue vent pipe of a gas water heater, it can collect on the top of your tank. This can happen especially during a storm with high winds.
    • Condensation - When excessive condensation occurs your water heater may appear as though its leaking. Condensation may be the result of the water heater not being able to meet the household's hot water demand.