7 Signs your water heater is going to explode

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Signs your water heater is going to explode

Your water heater might be a ticking time bomb. 

Let’s face it, we all love our water heaters. Without them, we can say goodbye to hot showers and hot dishwashing. But what happens if you don’t take care of these precious gadgets? That’s right, they explode! 

We’ve dealt with water heaters for quite some time now, and if there’s one thing we’ve learned, they are as destructive as they are helpful. 

Lucky for you, you don’t have to see their bad side. With some knowledge, you can learn to read the signs your water heater is going to explode and prevent it long before it happens. 

Read on as we go through everything about water heater explosions. We’ll review what causes them, how to read the signs and prevent them from happening.

Signs your water heater is going to explode

  • A Rotten Egg Smell
  • Continuous Popping and Knocking Sounds
  • Brown Rusty Water
  • Leaking Pressure Valve
  • Botched Installations
  • A Leaking Tank
  • When the T&P Relief Valve is Always Open

What causes a Water Heater to Explode?

When you installed your water heater, probably the last thing on your mind was that it could ever explode. But did you know that exploding water heaters are among the top five causes of residential water systems damage? Here are a few things that could cause your water heater to explode.

1. Excessive Internal Pressure

If you have an excessive pressure buildup in your water heater, it will eventually explode. Water heaters come equipped with a pressure and temperature relief valve. Despite this fact, extreme pressure might still overcome the valve’s capabilities.

If you notice that your pressure and temperature relief valve is leaking, you might have a pressure problem. In most cases, pressure buildup is caused by excessively high temperatures. You can avert this risk by setting your water heater’s temperature to about 120 – 125 degrees.

2. Sediment Buildup

Over time, minerals from hard water accumulate and build up in your water heater’s heating element. This results in an insulating effect that causes the water heater to work harder than it should. This can cause your water heater to overheat, thus causing an excessive internal pressure buildup.

3. Rust Corrosion

Water heaters are typically made of steel. Although steel takes time to rust, rusting is still inevitable. To curb this, water heater manufacturers equip their products with a sacrificial anode rod to slow down this process. But, with time, the anode rod becomes worn out, and the rust starts attacking the tank itself.

If placed in an unsuitable location, your water heater tank might also start rusting from the outside. With time, the rust affects the tank’s structural integrity, thus increasing its chances of exploding.

4. High Limit Switch Failure

If you look above the thermostat, you’ll see a large red button. That’s the high-limit switch. If your water heater’s thermostat is not working correctly, the water temperature might rise to unsafe levels. When this happens, the high limit switch trips and cuts power to the heating elements, thus averting danger.

In case the high limit switch fails, water temperatures might exceed set levels, resulting in pressure buildup within the tank, which, in turn, might cause the heater to explode.

However, this is an improbable scenario since water heaters come equipped with pressure and temperature relief valves. For this scenario to occur, both the valve and the high limit switch must fail simultaneously.

That being said, older water heater models might lack one of these systems, thus increasing the probability of an explosion.

5. Flammable Liquid, Propane, or Natural Gas Leaks

This problem is limited to propane and gas-powered units. These units have incoming and internal gas lines, not to mention fittings where leaks can develop. Gas leaks can be easily identified through a ‘rotten egg’ smell emanating from the bottom of the heater.

Since natural gas and propane gas are generally colorless and odorless, manufacturers add mercaptan, a smelly chemical, which gives them a ‘rotten egg’ smell.

When gas leaks occur, even a tiny ignition can lead to an all-out explosion. This is true even for liquid, flammable substances since the pilot light can also ignite them.

Signs your Water Heater is About to Explode

1. A Rotten Egg Smell

As we said earlier, although the gas used to power water heaters is odorless, manufacturers add a chemical to make it smell like rotten eggs or sulfur to alert you in case of a gas leak.

 If you smell rotten eggs near your water heater, chances are you have a gas leak. Therefore, you should turn off the gas immediately and call a professional before things get ugly.

2. Continuous Popping and Knocking Sounds

Using a tank water heater continuously for about a year without draining can result in sedimentation at the bottom of the tank. This mainly occurs in areas affected by hard water. So, if you live in such areas, you should have a water softener installed.

Although water heaters produce some sound, this one is pretty different. It sounds more like a popcorn machine. Sediments mostly accumulate close to the burner.

This results in the heater overworking to get the water hot. As this occurs, air bubbles form at the bottom of the sediment buildup. The pop sound is a result of the air bubbles trying to escape.

3. Brown Rusty Water

Pure water should be colorless and odorless. That being said, you shouldn’t be surprised to see brown water coming out of your unit.

Water heaters are equipped with an anode rod that attracts the molecules responsible for rust.

Over time, this anode rod becomes worn out, leaving the internal components of your unit susceptible to rust. With time, your water heater’s tank becomes too weak to contain the pressure within, thus leading to bursts.

4. Leaking Pressure Valve

The pressure relief valve is installed as a safety precaution. Its primary purpose is to control the pressure inside the tank. When the pressure in the tank becomes too much, the valve opens to ease tension.

At times, the valve may leak some water. But, if this happens over a long period, the valve can no longer handle the pressure in the tank, thus increasing the possibility of an explosion.

5. Botched Installations

If your water heater was not correctly installed, it’s bound to break down. In most cases, botched installations are a result of rush jobs and unqualified handymen.

Poor installation can lead to gas leaks and pressure buildup inside the tank. In some cases, poor wiring, as in the case of electric water heaters, can cause the system to short circuit. All these are potential causes of water heater explosions and, therefore, should not be taken lightly.

6. A Leaking Tank

A leaking tank is a sign that the tank is severely worn out. This can be either due to age or damage. The leaks may emanate from a crack or pinhole. Nevertheless, no matter how small the leak is, it still poses a threat of explosion since the leaking area is a significant weak spot.

7. When the T&P Relief Valve is Always Open

The temperature and pressure relief valve only opens when the internal pressure becomes too much when working properly. It also opens when the temperature levels are too high to allow cool water into the tank. In both cases, the valve closes once the internal tank conditions are back to normal.

If the temperature and pressure relief valves are always open, that might indicate that the internal temperature and pressure levels are too high and might lead to an explosion.

Tips to Avoid Water Heater Explosions

1. Flash out Sediments

Sediment buildup occurs on all tank-type water heaters. This is especially prevalent if you live in a hard water area.

If you don’t clear sediment from your water heater, it will eventually build up. Sediment buildup can lead to corrosion of the tank and failure of the electrical element. When the sediment layer becomes too thick, you might start hearing continuous popping sounds from your water heater.

 If left unchecked, the effects of the sediment buildup can cause your heater to explode.

Experts recommend draining your water heater annually. But, if you live in an area affected by hard water, you should flush the tank at least four times a year to prevent buildup.

2. Insulate your Water Heater Properly

Insulating your water heater is a great way to save energy and prevent your water heater from overworking. You can also wrap your hot water pipes to minimize energy loss. With that being said, you should be careful when insulating your water heater. Follow these rules for maximum safety.

  • Don’t insulate the top of your water heater.
  • Don’t insulate the control panel, drain, or temperature relief valve
  • Keep the pipe wrap at least six inches from the heater’s flue exhaust and gas draft hood
  • Always keep the air intake and pilot light access open

3. Test the T&P Valve Regularly

If your water heater has weak spots or any loose connections, it can explode. For this reason, water heaters come equipped with T&P valves.

T&P valves act as a failsafe by allowing excess water to flow out of the tank, thus relieving extra pressure.

However, excess sediment buildup, corrosion, and improper installation can cause the T&P valve to stop working correctly. When the T&P valve stops working, your heater becomes a ticking time bomb.

You should, therefore, regularly check whether the T&P valve is working correctly. Always be careful when checking the valve to avoid getting burned.

You can check the valve by lifting the handle to ensure that water flows out of the tank. When you drop the handle, the valve should seal itself shut and cut off all water flow.

4. Keep the Space around your Water Heater Clean

It doesn’t matter whether your water heater is electric or gas-powered. It could still be at risk of explosion. Electric sparks, gas leaks, and damaged heating elements can all cause fires. You should, therefore, keep all flammable materials away from your water heater to minimize the risk of combustion.


Although rare, a water heater explosion can be pretty devastating. You don’t want to lose your home because of a faulty appliance, do you? Always look out for signs your water heater is going to explode.

In the article, we’ve discussed a few signs your water heater is going to explode. If you see any of the symptoms mentioned above, turn off your water heater immediately and call a professional. You never know; it could just save you thousands of dollars in repairs and medical bills.

Frequently Asked Questions

Are water heater explosions common?

Water heater explosions are pretty rare. But, when they happen, the effects can be devastating, even fatal. It is, therefore, advisable that you check for any signs of an imminent explosion and deal with them immediately.

What happens when a water heater explodes?

For minor explosions, the tank raptures the pipes connected to it and spews water into the room. But, for more severe explosions, the tank might fly out of its hinges and cause significant damages to the house. Gas-powered heaters might even burn down the house.

Is it normal for water heaters to produce noises?

Yes. Water heaters do produce some sounds, especially when the tank’s volume is reduced. This is caused by water bubbles rattling around at the bottom as steam tries to rise. That being said, continuous popping noises should get you concerned.

Can I flash my water heater without calling a professional?

Yes. Flashing a water heater is pretty straightforward. All you have to do is turn on the cold water spigot and let it run for a few minutes. At first, you will notice that the water coming out is a bit unclear. Sediments cause indistinct coloring. It would be best if you did this until the water turns clear.

How long should I wait before replacing my water heater?

Typical water heaters last up to 15 years. That being said, you should replace it sooner if you notice any defects. It would help if you also replaced it when you start running out of hot water faster. This is primarily due to sedimentation or the heating element not working correctly.

What causes a water heater to explode?

Water heater explosion can be caused by:

  • Excessive sediment buildup
  • Rust corrosion
  • Faulty T&P valves
The H2Home Lab team is dedicated to helping you find the best solutions to your specific water needs, as well as provide troubleshooting tips and guides for water filtration, heating, softening and plumbing. We hope you will find the info you need on our site from any one of our buying guides or subject matter articles.

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