Water Heater Leaking from the Top: Everything You Should Know

Water Heater Leaking on Top

There's no denying it, finding a puddle of water around your water heater is depressing. But, if you found your water heater leaking from the top, well that might not be as bad as you think. Frequently, when a water heater leaks from the top it's a fixable problem. It is also a less expensive problem. However, if the leak isn't  promptly repaired it could lead to a serious issue if the water finds it's way into the electrical compartment.

Furthermore, you could be dealing with serious and costly water damage to floors and/or walls that are nearby. 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.

Water Heater Leaking from Top

Safety First

If you have an electric water heater, you’ll need to locate the circuit breaker on your electrical panel and switch it OFF.  If you have a gas water heater, turn the thermostat control knob to OFF.

Do not turn OFF the incoming water until you locate the leak. It may seem counterintuitive, but turning off the water will make it difficult to locate the leak.

Finding the leak
  • With the power shut off and the cold-water inlet valve* still on, dry the top of the water heater.
  • Then place a paper towel along the top of the heater to help identify the leak. This can be especially handy if the leak is not visible.
  • Thoroughly inspect the seals and pipes leading to the water heater.
  • Once you have located the leak, turn off the cold-water inlet valve to prevent further water damage. 

* Cold-Water Inlet Valve - Located on the cold water pipe that supplies water to the water heater. It is usually a lever or a knob type valve. Some water heaters do not have this valve installed, in these cases you'll need to shut off the water to the entire house. 

Causes and Fixes 

Cause 1: The Cold-Water Inlet Valve

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

The fix for a dripping leak at the inlet valve is often as simple as tightening the valve (that is, the nut that connects the handle).

If the leaking persists after tightening, then you may have a defective valve which will need to be replaced. 

Cause 2: The Pipe Fittings or Connections

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 buildup of rust.

The Fix

If the pipe connection is loose, then use a wrench to tighten it. This should stop the leak. However, if the fitting is corroded, then you would have to replace the fitting. This should not be difficult, unless the fitting becomes very difficult to remove or if copper tubing was used instead of threaded pipe.

Cause 3: The T&P Relief Valve

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

It is usually located on the side of the tank, but sometimes it's on the top. When looking for a leak, check at the following:

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

If you have a leak from your T&P valve, the leak would originate:

  • At the base where the T&P valve connects to the heater, or
  • From the drain pipe attached to the T&P valve.
Leak From The Base

If you notice water leaking from the base, you should first open the T&P valve and allow it to flush away any debris. If after flushing, it continues to leak, you should replace the valve. There's a good chance that the threads of the existing valve are the culprit.

How to replace your T&P valve

  • Check that the water heater's power and water are turned off.
  • Let the water cool and 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. Check for signs of rust or corrosion.
    • If you found evidence of rust or corrosion, then you'll need to replace your water heater. 
    • If you did not find rust and corrosion, wrap Teflon tape on 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. 
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 is 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

Cause 4: The Anode Rod Port

Water heater tanks are made of steel, and steel will rust. An anode rod is a long, thin, solid pipe that is 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, it is 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.

Cause 5: The Expansion Tank

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 becomes too high. The high pressure could damage valves, joints, and even the water heater.

An expansion tank prevents this from happening by taking in heated water to ensure that the water pressure in the heater does not increase significantly. Expansion tank leakages usually occur at any of these 3 areas:

  • 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 from the threaded connection:

  • Remove the expansion tank from the connection point.
  • Apply thread sealer to the threads.
  • Then 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.

What Else Could Be Causing 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:

  • Rainwater - When rainwater 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. This may be a  result of the water heater not being able to meet the household's hot water demand.