Water Heater Leaking From The Top – What Causes It And How To Fix It


Almost 75% of water heaters fail within the first decade. There are several components on the top of a water heater that can be the cause of the initial leak, and fixing the problem can improve the longevity of your water heater.

Water leaking from the top of your water heater is most likely the result of a malfunctioning temperature and pressure (T&P) valve. However, water heaters can also leak from the top due to a damaged or loose cold water inlet valve, loose pipe, an oxidized or corroded anode rod, leaking expansion tank, or in rare cases, a damaged internal tank.

This article gives a detailed explanation on how to locate the cause of the leak at the top of your water heater. It also gives clear step-by-step instructions on how to fix each potential problem. 

How to locate the source of the leak at the top of your water heater

  1. Turn off the water heater power supply
  2. Turn off the thermostat if your water heater has one (usually gas water heaters)
  3. Locate the cold water inlet valve and make sure that it’s ON for easy spotting of the leak. The valve is usually located on the pipe that leads to the water inlet source
  4. Wipe dry the areas around your water heater for accurate diagnosis in case of previously spilled water. You can also use a paper towel to trace and spot the exact source of the water leak.
  5. Check pipes, seals and every other part that make up the top of your water heater
  6. When you find the leak source, turn off the water inlet to contain the damage

6 Reasons Why Water Is Leaking From The Top Of Your Water Heater

1. Malfunctioning temperature and pressure (T&P) valve

The T&P valve is a safety component that activates only when there is high temperature or pressure in the water heater tank.

The valve can be located either at the top or the bottom of your tank, so this can only be the source of your leak if the T&P valve is located on the top of your specific water heater. 

A functioning T&P valve should release water through the discharge pipe of the water heater.

However, if your temperature and pressure valve is damaged or malfunctioning it will not release the water when needed.

The T&P valve can leak directly from the point where it is screwed in to the tank or from the pipes. Either way, it needs to be replaced as soon as possible to prevent your tank from bursting due to high pressure.

To replace the temperature and pressure valve, you’ll need a new valve, channel locks, and teflon tape.

  1. Drain the water heater tank
  2. Open a hot water tap somewhere in the house to let air into the tank and release pressure
  3. Use channel locks to unscrew the valve from the tank
  4. Check for corrosion or rust on the part where you unscrewed the valve. If there is s rust then you may need a new water heater, and not just a T&P valve fix.
  5. If there’s no corrosion, wrap the threads of the new valve with Teflon tape to get a proper seal and then screw it back to the water heater tank.
  6. Connect the water heater to the appropriate power source and turn it on.
  7. After this, be sure to monitor the water heater to confirm that your water heater is no longer leaking.

2. Damaged water inlet valve

The cold water inlet valve is the part of your water heater that is connected to the main water line in your home.

Wear and tear to this valve, or visible damage can cause water leaks in the form of droplets and drips on the top of your water heater. Water drippings indicate that you need a new valve. 

If you notice water pooling at the top of the water heater, then the water pipe might be loose. In this case, try to tighten the fitting that connects the handle/valve and monitor the leaks.

If the water heater continues to leak after tightening, then you will need a new valve.

3. Loose pipes and fittings

There are different pipes connected to the top of your water heater.

Check all the fittings on the water outlets and inlets.

If you notice leakages from these points or any other connection point on the top of the water heater, you need to tighten the affected fitting.

If this doesn’t solve the problem, and your water heater continues to leak, then there’s a possibility the fittings have corroded or there is a build-up of rust. If this is the case you will need to replace the entire pipe fitting or the water heater (depending on the level of corrosion).

4. Corroded anode rod and screw

The anode rod is a long, thin rod that stays inside the water heater tank and prevents it from corroding. It does this by attracting all corrosive agents in your water source to itself and keeping the tank safe.

Ideally, you should pay particular attention to the anode rod and screw and change it as soon as it starts corroding. 

If a corroded anode rod is not changed immediately the rust can reach the top of the rod. Water then starts to form bubbles at the connection point on the water heater.

Once the anode rod screw is rusted or the rod is covered in rust, your water heater tank is no longer protected from the corrosive agents in your water. This is often an indicator that without professional intervention, your water heater is about to fail.

Therefore in the case of a corroded anode rod or screw, it is best to engage a plumber to determine if you’re only changing the screw or the hot water heater altogether. 

5. Leaking expansion tank

If your water heater comes with a smaller tank called the expansion tank, then it is a potential source of water leaking from the top of your water heater.

The expansion tank is also a safety component whose main function is to lower pressure and hold any excess water from the water heater tank during the expansion of water as it is heated.

This tank usually starts to leak as a result of general wear and tear. 

The first thing to do here, just like the actual heater, is to verify the origin of the leak.

If the leak is coming from the pipes, tighten the fittings on the expansion tank with a wrench and observe for changes.

If the problem is from the tank itself, get a professional to help as the pressure within this tank needs to be set properly for it to function optimally.

6. Damaged or clogged internal tank

If the tank itself is leaking due to sediment build-up, corrosion, or cracks, you will need a new tank. You can hire a plumber to confirm the problem or get a new water heater if you are sure of the internal damages.

Will a leaking Water Heater Explode?

A leaking water heater will only explode if the leak originated from a leaking T&P valve, damaged anode rod or a damaged internal water tank due to sediment build-up. In these circumstances, the water heater explodes due to excess water pressure within the internal tank.

Optimum pressure regulation is what keeps your water heater in good shape. A pressure gauge can be installed on the drain valve outlet of the water heater to monitor the water pressure.

Once installed, the water pressure can be checked by opening the drain valve, closing the cold-water inlet shut off valve to the water heater and watching the pressure gauge to see if the pressure is maintained, or if it drops sharply.

What is the plug on top of my water heater?

The top of your water heater usually holds two main valves: the cold water inlet valve and the temperature and pressure (T&P) valve. The cold water inlet valve connects directly to the main water supply, whereas the T&P valve releases water through the discharge pipe to regulate the temperature and pressure in the heater.

Why is my anode rod leaking?

The anode rod is a protective device for your water heater tank that requires routine changing. If you don’t change it at the appropriate time, the corrosion reaches the top of the anode rod and water bubbles start to form at the top of your water heater, eventually leading to leakages. A leaking anode rod or screw requires immediate replacement to save yourself the cost of a new water heater.

Conclusion

Water heater leaking from the top is often considered a better scenario than a water heater leaking from the bottom. However, in both cases, time is of the essence. As long as you can catch a malfunction early and fix it almost immediately, you’ll be saving yourself a lot of damages.

Recent Posts