Water Heater Leaking? How to Fix It — A Definitive Guide

Your water heater leaking may not be the end of the world. Find out why.

Have you noticed wet patches around your water heater lately? Not many of us make a habit of spending time near our water heater, so it’s possible you may not. We want you to take a second right now and check your water heater and the floor around it.

Welcome back, did you notice any water? Read on if you did. Even if you didn’t, I still recommend you read on because it’s important to know what to do if your water heater is leaking.

We’ll go over the hazards of leaky water heaters, how to detect leaks, and what to do about them. There are a few different possible leak spots and each has its own reason and repair technique.

Why Your Water Heater Is Leaking

Water heaters can leak for several reasons. It’s important to maintain them to avoid this as it’s a problem that will only get bigger. Even if the leak seems insignificant, it should still be taken care of right away.

Untreated leaks can lead to mold, which can cause asthma and other breathing issues to flare up (1). Mold can also be costly to clean up if it isn’t taken care of right away.

However, in certain situations, there may not be a leak at all. Rainwater can sometimes get in through the pipes after a big storm and cause water drippage on your unit. To rule out rainfall, simply wipe down the unit and keep an eye on it for a few hours.

Leaks From the Overflow Pipe

You may notice water is flowing through the pressure relief valve and exiting through the overflow pipe. In this case, it’s likely to be because there’s too much pressure inside the tank for the unit to handle.

Your unit’s pressure relief valve works to make sure the pressure is stable. It relieves excess pressure by draining off water through the overflow pipe. If it doesn’t do this, your water heater can explode from the pressure (2).

If you think this is your issue, here’s what you can do.

  1. Turn the thermostat to the lowest setting.
  2. Turn on the water supply and power.
  3. Observe the heater over a short period.

If the problem persists, you’re going to need to call a professional to come and inspect the issue.

Leaks From the Top

If you’ve noticed water leaking on the top of your water heater, there are a few possible causes. To figure out the culprit, start by turning off the power to your water heater.

The power should be off, but you shouldn’t turn off your incoming water until you can find the source of the leak. To find the leak, here are a few simple procedures to follow.

  1. Dry the top of the water heater with a towel.
  2. Place a paper towel along the top to find the leak.
  3. Inspect the seals and pipes leading to the water heater.
  4. Once you find the leak, turn off your incoming water to prevent further damage.

Finding the source of the leak is your first step, but you still have to fix the issue. Here are the most common causes of tank top leaks and how to fix them.

1. Cold Water Inlet Valve

This is what allows cold water to flow into the heater. When this is turned off, it blocks the water flow. If you see water dripping at the top of your water heater, it’s probably an inlet valve leak.

To fix this issue, you may just need to tighten the valve. This can easily be done with a wrench. If the issue continues, the part is probably damaged and needs replacing.

2. Pipe Fittings or Connections

With time, the fittings and connections around your unit can become loose or corrode. You can tell that it’s corroded if there’s a white substance around the area. Rust is also an obvious indicator.

If it’s loose, simply tighten up the connection causing the issue. However, if it’s corroded, you’re going to want to just replace the part.

To replace your pipe fittings, you should call a professional. However, if you’re comfortable, you can do it yourself by following these steps:

  1. Use a bucket to drain your hot water.
  2. Turn off your cold water shut-off.
  3. Turn on all hot water faucets in the house.
  4. Cut the pipe to remove the corroded connection.
  5. Use a pipe wrench to carefully remove the corroded part.
  6. Use Teflon tape to cover all of the threads on your new connection piece.
  7. Connect your pieces and solder your connection points to prevent any leaks.
  8. Turn the water and power supply back on.

3. Anode Rod Port

Anode rods are made of aluminum or magnesium and are used in water heaters to protect against corrosion. These will themselves corrode over time so they’re often referred to as “sacrificial anode rods” (3). Because they will corrode, these should be checked during regular maintenance.

If it isn’t replaced when you first notice corrosion, you’ll end up with a leak at the port where the rod sits. To fix this issue it’s normally just a case of replacing the rod. However, if you notice extensive corrosion, then you may want to consult a professional.

4. Expansion Tank

The main purpose of expansion tanks is to keep your water heater from bursting. These also help keep even pressure throughout your unit. Not all units have an expansion tank, but they work similarly to a pressure relief valve.

They’re designed to absorb any excess hot water. When hot water expands and isn’t checked regularly, it can cause damage to your heating system. Expansion tanks help relieve that, but if there’s a leak within it, it can’t do its job properly.

If the leak is in the expansion tank, you’ll see it in one of three spots.

  • The threaded connection: If this is the case, remove the expansion tank at the connection and apply thread sealer to the threads. Tighten the expansion tank back in place and the issue should be resolved.
  • The air valve opposite the threaded connection: If the leak is here, you’ll need to call a professional to replace it.
  • The actual tank: This is another situation that would require a professional.

Leaks From the Bottom

If you notice a leak from the bottom of your tank, the most important thing to do is find the source of the leak. Here are some of the most common causes of bottom leaks.

1. Leaking Drain Valve

All water heaters will have a drain valve near the bottom of the unit. These are meant to aid in emptying the tank for removal or annual maintenance. It’s pretty easy to tell if this is where your leak is coming from because you’ll see dripping from the valve.

You may also find water around the spout as well. To fix this issue, turn the valve control clockwise to close it. If you’re still experiencing a leak, the entire valve probably needs to be replaced.

If you need to replace the valve and you don’t want to call a professional, there’s an easy way to do it.

  1. Connect the water hose to the tank and another outside location.
  2. Turn off the tank’s water inlet. You can typically find this on the top of the water heater.
  3. Open the drain valve and let it empty.
  4. Once it’s empty, use a wrench to turn the valve counter-clockwise to remove it.
  5. Wrap the threads of the replacement part in plumbers tape.
  6. Screw in the new valve by hand until tight.
  7. Use your wrench to tighten it more. We recommend a half turn or until you can’t tighten it anymore.

2. Leaking Pressure Relief Valve

The pressure relief valve is responsible for regulating your water pressure when the water gets too hot. This is an essential feature for safety, so it’s important to make sure it’s working properly.

The pressure relief valve is found on the top of your unit with a tube that guides water to the floor. You’ll know your pressure relief valve is leaking if there’s water on the floor underneath your tank.

In this case, check the thermostat and make sure it isn’t set too high. If the temperature is normal, you will need to replace the valve. This is something you can do yourself by following these steps (4).

  1. Turn off the power supply.
  2. Close the cold water cut-off valve.
  3. Open the bottom valve and the pressure relief valve for one minute to drain the area.
  4. Remove the overflow pipe from the pressure relief valve.
  5. Use a pipe wrench to unscrew the old valve.
  6. Wrap Teflon tape around the threads to prevent leaks and rust on the new valve.
  7. Reattach the pipe to the new valve.
  8. Open the cold water cut-off and check for any more leaks.

3. Leaking Tank

A leaking tank poses the biggest issue because it probably means you’re going to need to replace the entire unit. If you don’t take care of your water heater tank, salt and other build-ups can cause the tank to corrode. This can cause pinhole leaks in your unit (5).

The leak will start small. With the amount of pressure constantly pushing on it, though, it’s going to get worse over time. If you’ve noticed these leaks, you’ll need to replace the entire water heater.

We recommend hiring a professional to do this. However, if you need to pinch pennies, it’s possible to do it yourself. Here’s how:

  1. Remove the plumbing connected to the heater.
  2. Disconnect the power from the access panel.
  3. If your water heater is gas, make sure to turn off the gas line leading to your unit.
  4. You’ll then disconnect the gas line from your unit.
  5. Replace the unit and reconnect the pipes and power.

4. Condensation

Condensation is another issue you may find with water heaters. Your boiler location should not be too cool and well ventilated to prevent condensation occurring.

Additionally, if your unit is old, you’ll see that condensation is more common. Still, it can also occur with newer models if the insulation is damaged or the thermostat is too high.

Here’s what you can do if you see condensation:

  1. Let the unit sit idle with the power and gas shut off for a few hours.
  2. If the water stops, it’s condensation. Just lower the thermostat and turn the power back on.
  3. If the issue doesn’t resolve, you may need to replace the unit with something more insulated.

Condensation can also occur short term when a new unit is installed. If the water filling the tank hasn’t had the chance to heat up yet, it needs time to catch up.

Check Your Water Heater

Homeownership is all fun and games until you run into maintenance issues. Nobody likes spending big bucks on replacing household appliances, including water heaters.

But it’s important to perform annual maintenance on your water heater. This helps you to prevent issues arising and quickly become aware of any that do.

At the first sign of your water heater leaking, identify the source and fix the issue. In many cases, you may just need to tighten a valve or connection. However, if you notice corrosion, some parts may need to be replaced.

Sometimes it’s inevitably going to be a problem you can’t resolve yourself. So, although it will cost, it’s always advisable to consult a professional when there’s any uncertainty.

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About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.