Can Your Water Heater Explode?

Is your water heater dangerous? You might have heard stories about water heaters exploding and shooting like a rocket through the roof of someone’s home. Are they true? Is owning a water heater like living with a potential ticking time-bomb in your basement?


It’s true, water heaters can explode. Find out how they work, what causes them to explode, and how you can avoid this from happening to you.


How Does a Water Heater Work?

Before getting into what causes a water heater to explode, first you need to understand how they work.


There are two basic types of water heaters—gas and electric. Every different model of water heater will operate in a slightly different way, although all water heaters use similar principles. The basic process all water heaters use is some form of combustion to heat water inside the holding tank.


Gas heaters use a burner to heat stored water inside the tank. Electric heaters use coils to heat the water. Once the water inside the tank reaches the ideal temperature, the burner turns off. The temperature, the gas or coils will heat the water inside the tank to will be determined by the person operating the water heater.


For most water heaters, the manufacturer recommends setting the temperature no higher than 120 degrees Fahrenheit.


What Does Each Part Do?

To simplify the process a water heater takes, here is a breakdown of each part and an explanation of what it does.

  • Copper Piping: Your water heater uses two pipes—an incoming cold water pipe and outgoing hot water pipe. These pipes are usually copper and located on the top of the tank.
  • Dip Tube: On the inside of the tank the dip tube distributes the cold water into the bottom of the tank. If the tube deteriorates or breaks it won’t heat the water properly.
  • Anode Rod: To protect the dip tube and tank from minerals in the water that deteriorate metal, an anode rod is installed inside the tank. Do not remove this although it may smell like sulphur. The anode rod attracts corrosive minerals that will deteriorate the rest of your tank, but can eventually lead to strange smells.
  • Drain Valve: A drain valve is located at the bottom of the tank. Minerals that build up in the tank sometimes cause a loud knocking or banging sound. Although this sound is normal, the drain valve should be opened to flush the water every few years and release mineral build up.
  • Pressure Relief Valve: The pressure relief valve is located at the top of the water tank. This valve is a safety feature meant to relieve pressure and stabilize the system when pressure or heat becomes too high for the tank to handle. If either of these valves are leaking, replace them immediately. If the tank develops a leak, shut off the cold water supply to prevent flooding.
  • Discharge Tube: A discharge tube must be installed on the pressure relief valve and placed 6” above the floor. This is another safety feature that prevents scalding water from spraying out and injuring someone.


Gas heaters using a pilot are regulated with a thermal couple or a thermal pile. As the temperature decreases in the tank, gas is released and the pilot lights the burner, which heats the water inside the tank. When the pilot goes out the thermal couple or pile will prevent the gas valve from opening. If the pilot goes out it will need to be relit following the manufacturer’s instructions.


Some newer models allow you to use a switch that re-ignites the pilot. Older water heaters will need to be manually lit using a long lighter. The pilot light is usually located at the bottom of the tank.


Water heaters using gas need to exhaust carbon monoxide through a flu to the outside of the home. If the flu is damaged, it can cause carbon monoxide to leak into your house. Install a carbon monoxide detector in your home and check it regularly to avoid any issues with potential leaks if you use a gas water heater.


What Causes a Water Heater Explode?

If the temperature is set too high or the pressure relief valve of a water heater malfunctions, a water heater can explode. This can happen with a gas or electric hot water heater. The pressure relief valve will malfunction if it the pipe is blocked or the pressure is otherwise unable to release.


As water heats up it turns into gas. Once the heat and pressure become too much for the tank to withstand it attempts to release the pressure through the relief valve. If the valve is blocked or broken in any way, the internal pressure grows until ultimately exploding.


The damage it can cause is significant. It has the ability to compromise your entire home. Although it is unlikely for water heaters to explode, when they do, they operate much the same as a rocket. It will blow a hole through your ceiling and the tank itself may end up several blocks away. It is very dangerous.


Always check your hot water heater’s pressure relief valve to ensure it is in good working condition. If you have any concerns that your water heater is not functioning accurately, have an inspector come take a look at it.


The best precaution you can take to avoid having this happen to you, is to set your water heater’s temperature no higher than your manufacturers suggested setting.


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