Can a Water Heater Explode? The Signs to Look For

A water heater (if properly working) will always have hot water in the tank. The thing about hot water as opposed to cold water is that it expands.

When the hot water expands, it exerts pressure inside the tank. This is nothing to worry you since the water heater is made of thick steel, which is more than enough to accommodate this expansion.


Apart from that, the water heater is fitted with safety devices to release pressure from the tank and others to cut off gas or electricity supply in case of an unsafe condition.

A properly installed and maintained water heater is not likely to explode. If however the water heater maintenance is neglected and/or it is not properly installed, the potential to explode is quite high.

The following are the reasons why a water heater may explode:

  • Excessive Pressure: The most common cause of a water heater explosion is excessive pressure inside the tank. This can result from a malfunctioning pressure relief valve or a faulty thermostat that allows the water temperature to rise too high.
  • Sediment Buildup: Sediment, such as minerals and debris, can accumulate at the bottom of the tank over time. This sediment can create hot spots, causing localized overheating and weakening of the tank.

Signs to Look Out For:

  • Leaking Pressure Relief Valve: If you notice that the pressure relief valve is leaking or discharging water, it may be a sign of excessive pressure within the tank. This is a critical warning sign that should not be ignored.
  • Popping or Rumbling Noises: Unusual noises coming from the water heater, like popping or rumbling sounds, can indicate sediment buildup at the bottom of the tank. This buildup can lead to overheating and pressure issues.
  • Corrosion and Rust: Inspect the water heater’s tank for signs of corrosion or rust. Corrosion can weaken the tank’s structural integrity, making it more prone to failure.
  • Water Leaks: Any signs of water leaks around the water heater should be addressed immediately. Leaks can indicate a failure in the tank or plumbing connections.
  • Fluctuating Water Temperatures: If your water heater struggles to maintain a consistent temperature or produces excessively hot water, it may be a sign of a malfunctioning thermostat or pressure relief valve.
  • Old Age: Water heaters have a finite lifespan, typically around 10-15 years. If your unit is approaching or exceeding this age, it may be more susceptible to issues, including pressure-related problems.

So, when should you replace your water heater and when should you fix it? I have written a detailed article on that as well. Read it here.

Signs that a Water Heater will Explode


What are the telltale signs that a water heater is on the verge of exploding? Let us look at them one by one.

1. Leaking Temperature and Pressure Relief Valve

A water heater temperature and pressure relief valve is a safety valve located either on top of the tank or on the side near the top. It will also have a vertical discharge pipe connected to it.

The function of a T&P or TPR valve as it is also called is to discharge excess pressure and temperature from the tank, making it safe. The rating of a TPR valve is usually 2100 F and 150 psi.

If the water inside the tank exceeds this rating, the TPR valve opens and discharges some water through the discharge tube. Some discharge water on a pan at the bottom of the tank while others are connected to an exterior pipe.

A TPR valve discharging water through the discharge tube should not be mistaken with a leaking TPR valve. The problem happens when the valve is leaking around its connection to the tank.

If you live in an area with hard water, the valve will corrode, lose its integrity and start to leak. When the problem is not fixed as fast as it should, the pressure in the tank will exploit that weakness and blow up through it.

A leaking TPR valve is not as dangerous as one which is faulty. A faulty TPR valve will not discharge water from the tank even when it exceeds its rating. This usually happens when the valve is clogged by mineral deposits.

To check if your TPR valve is working, place a bucket under the discharge tube and gently lift the TPR valve lever. If water is discharged in the bucket then the valve is in good condition. On the other hand if no water flows out, the valve is faulty and will need a replacement immediately.

I have written a detailed post on the water heater temperature and relief valve including when and how to replace it. Read it here.

2. Rotten Eggs Smell

If you use a gas water heater, the worst thing you can have is a gas leak. Natural gas suppliers are mandated to inject the gas with a substance which makes it smell like sulfur or rotten eggs for easy detection in case of a leak.

Gas water heaters are however designed to automatically shut off the gas control valve if the pilot light goes out. The way a gas water heater works is that the pilot light ignites the gas flowing to the burner, meaning if the pilot is off the burner will be off as well. But the natural gas will also stop flowing to the burner.

What makes this possible is the thermocouple. The thermocouple is placed very close to the pilot. The heat from the pilot generates a current in the thermocouple which activates a spring in the gas valve, ultimately keeping the valve open.

If the pilot light is off, the current in the thermocouple will die off, causing the thermocouple to turn off the gas valve. The thermocouple therefore acts as safety feature as well.

A poorly installed or maintained gas line could start leaking and if the gas comes into contact with the pilot light or any other source of ignition an explosion could occur.

If you every notice a rotten eggs smell in the and around your water heater, shut off the gas supply immediately. Open all the doors and windows and contact the gas company or a licensed plumber.

3. Popping/Banging Sounds

Popping or knocking noises from your water heater is a sign of sediment buildup inside the tank. This happens when you do not drain/flush your water heater at least once a year as recommended.

The reason this is dangerous is because water can be trapped under the sediment and start boiling and building up pressure. What is worse is that the conditions under the sediment cannot be detected by the TPR valve causing the pressure to increase to dangerous levels.

The popping sounds are usually as a sign of the water boiling and bubbles trying to percolate through the sediment. This is what is likely to cause the explosion.

The water heater is usually fitted with an anode rod that you should replace after a few years as well. Water heater anode rods are for sacrificial purposes.

The elements in the water attack it instead of the water heater internal lining, thereby extending the life of the tank. If you fail to replace the anode rod, the integrity of the tank is compromised as it will start to corrode and therefore become weak

If you notice brown water when you turn on your shower or hot water faucets, this is usually the cause.

Sediment will sit at the bottom of the water heater and start to attack. With time, a hole will be formed and the tank will start to leak. If not replaced immediately the tank will weaken even more and as pressure in the tank builds up the tank could explode.

How to Prevent a Water Heater from Exploding

When you suspect your water heater may explode or shows signs like the ones I have outlined above, there are things you can do to avert the danger.

The first thing you should do is to turn off gas supply to your water heater if you are using a natural gas water heater or turn off power to an electric water heater. If there are combustible items in the room like fuels, clothes and other substances remove them.

The next step should be to turn off water to the water heater and then drain the tank. Remember that even if you have turned off power or gas to the water heater, you have 40 gallons or more of hot water in the tank.

That is enough water to scald and cause quite expensive water damages. To safely secure that water heater, connect a garden hose to the drain valve and drain the tank.

If your water heater is safe but you would like to prevent leaks and possible explosions in the future, here are things you can do:

Flush the Water Heater

Flushing a water heater is the process of draining the tank and in the process remove any sediments that may have accumulated.

It is advisable to flush a water heater at least once a year. I have written a guide on how to flush a water heater in more details. Find it here.

Adjust the Water Temperature

Both electric and gas water heaters have thermostats that helps you adjust the temperature of water inside the tank. as we have seen, high water temperatures means more pressure build up, which apart from increasing the risk of an explosion can badly scald.

The ideal water heater temperature is 120 degrees Fahrenheit. 130 degrees is also not bad. It will not scald you and is sufficient to kill bacteria in water.

Adjusting the water temperature in a gas water heater is easy since the thermostat is readily accessible. That is however not the same for electric water heaters. Luckily for you, I have written this guide to help you.

Install a Thermal Expansion Tank

A water heater expansion tank is a small tank (about 2 gallons) that is installed on your water heater’s cold water line. Its function is to store excess water pressure from the water heater to prevent buildup of the same.

The thermal expansion tank has an air bladder which separates compressed air and the cold water at the bottom. When water in the water heater starts to expand, it flows to the expansion tank and compresses the air bladder, effectively lowering the build up inside the water heater tank.

Do you need a water heater expansion tank? Read this post I wrote here to find out.

Schedule Regular Maintenance

Do not wait for the water heater to completely fail in order to have it maintained. Plan to have a licensed plumber check it at least once a year.

Another thing to do is to make sure that the water heater is serviced by licensed plumbers. As we have seen, this is a critical installation which can cost human life.

Lastly, if the water heater is older than 10 years, it has surely served you well. Go ahead and replace it with a new one.

Leave a Comment