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Why Is My Water Heater Leaking?

April 12, 2021

Wondering what’s causing your water heater to leak?

For tank water heaters, the most common cause of leaks are:

  • A loose cold or hot water inlet/outlet connection

  • A worn gasket or seal

  • High pressure in the tank

  • A cracked tank

For tankless water heaters, the most common cause of leaks include:

  • A loose pipe connection

  • Corrosion or rust

In this blog, we’ll explain each of these issues in more detail. We’ll also tell you right off the bat that most of these problems will require a professional diagnosis and repair. Since a leaking water heater can lead to water damage, we recommend contacting a plumber for help ASAP.


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Tank water heater leaking problems

Below are the top 4 causes of leaks in tank water heaters:

Cause #1: A loose cold or hot water inlet/outlet connection

At the top of your water heater, you’ll see two pipes going into it. One is the cold water inlet, where cold water enters into the tank. The other is the hot water outlet, where heated water exits the tank and goes to your plumbing appliances.

cold water inlet and hot water outlet pipes on a tank water heater

The cold water inlet and hot water outlet pipes on a tank water heater

Sometimes the connections on these pipes can get loose over time, causing water to leak around them. This could explain why you see water leaking from the top of the tank.

Solution: You can try to tighten the connections yourself using a wrench, but if the leaking problem persists, you’ll need to contact a plumber for further assistance.

Cause #2: A worn gasket or seal

Your water heater could also be leaking because of a worn gasket or seal. The most common places you’ll find a worn gasket or seal are:

  • The upper or lower heating elements on the side of the tank (only applicable to electric units)

  • The drain valve at the bottom of the tank

Cracked drain valve

The drain valve, located at the bottom of the tank

Solution: If your water heater is leaking from one of these places, contact a professional to inspect your water heater and replace any worn out gaskets or seals.

Cause #3: High pressure in the tank

If the pressure inside the tank gets too high, your water heater will automatically release some of the water to lower the internal pressure. The water is released via the Temperature and Pressure Relief (TPR) valve, which is located on the top or side of the tank.

The discharge pipe and TPR valve on a tank water heater

The discharge pipe and TPR valve on a tank water heater

The water released by the TPR valve travels down the side of the tank via the discharge pipe, which empties the water into a drain. If you see a hot, steady stream of water coming out the discharge pipe, then it means your water heater is trying to lower the pressure inside the tank.

Solution: You’ll need to contact a plumbing professional to find out what’s causing high pressure in the tank and repair the issue. If you see a small amount of water leaking around the TPR valve itself, that could mean the valve is faulty and will need to be replaced by a professional.

Cause #4: A cracked tank

Finally, your water heater may be leaking because the tank itself is cracked. Two problems can cause the tank to crack:

  1. Corrosion: Over time, the inner lining of the tank can corrode because of minerals in the water. This often happens at the bottom of the water heater, where mineral deposits settle at the base of the tank.

  2. High pressure or overheating: High pressure and temperatures can cause stress fractures in the tank, which can eventually form leaks.

Solution: Unfortunately, if the tank itself is cracked, there’s not much a plumber can do to fix it. In this scenario, the best option would be to replace the water heater.

Tankless water heater leaking problems

While tankless units are less likely to leak compared to tank units, they are not totally immune to leaks—especially if they are older.

Let’s look at the two most common causes of tankless water heater leaks.

Cause #1: A loose pipe connection

The connections on the cold water inlet and hot water outlet pipes coming into/out of the tankless unit can become loose over time—especially if they were not properly tightened to begin with.

Solution: You can try tightening the connections yourself with a wrench, but if the leaking persists, contact a professional for assistance.

Cause #2: Corrosion or rust

If your tankless water heater is old, then internal components may have corroded or rusted. Over time, minerals in the water supply can slowly corrode pipes or other components, causing them to develop leaks. If you see water leaking from the body of the tankless unit, it could mean an internal component has corroded.

Solution: Contact a plumber for assistance. Depending on the component that is leaking, a plumber may be able to replace the part. Or, if the corrosion is widespread, the plumber may recommend replacing the tankless unit altogether.

Ready to schedule a water heater repair?

Call (210) 293-5550 or schedule an appointment online today. We’ll send one of our skilled and highly-trained plumbers to find the source of the leak and repair it. If the repair isn’t done to your satisfaction, we’ll come back at our own expense and fix it again.

Learn more about our 5-star repair work by visiting our tank water heater repair page.

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