Without proper maintenance, your water heater can go from heating up your water to exploding under increased pressure. It's well documented and you can find a lot of stories about fatal injuries from water heater explosions in the news. The television show Mythbusters also showed what kind of damage an explosive water heater can do.
How does this happen though? Don’t worry – As long as you have maintained your water heater properly, you don't have to worry about it exploding from increased pressure!
Usually, a water heater will stop working and potentially burst when there is too much pressure built up inside of the tank. There's a safety valve in every water heater, called the Temperature and Pressure Relief Valve, or a T&P relief valve. In short, when the temperature or pressure of the water heater gets too high, the valve opens, and releases water that's causing the increase in pressure.
The problem is that many homeowners don’t realize they need to be testing their T&P valves every 6 months, and replacing them every 5 years.
WHAT IS A TEMPERATURE AND PRESSURE RELIEF VALVE?
T&P valves are a safety element built into every water heater. They make it so your water heater doesn’t become a ticking time-bomb … literally. Learn more about how a water heater works here.
A temperature and pressure relief valve opens in two cases. The first is temperature. When your water heater is working, cold water is brought into the tank, and a heating element heats the water. It is then pushed throughout your home through the hot water pipe. It’s a fairly simple design. However, sometimes things go wrong. There are times that the temperature of the water within the tank increases to a dangerous point. In this case, the temperature and pressure relief valve opens up, and drains the hot water, allowing more cold water into the tank, and decreasing the temperature.
The other time that a T&P relief valve opens is when there is too much pressure within the tank. When water heats up, it expands. Usually, water heaters are set to hold about 150 PSI (Pounds per Square Inch). When the pressure of the water inside of the tank goes over that, then the temperature and pressure relief valve will open, until the pressure is released. The danger begins when homeowners don’t test their T&P valves. A homeowner should test their T&P valve every 6 months to see if water is able to exit the tank through the valve, or if there is too much corrosion. Homeowners should also be replacing their T&P valves every 5 years in order to ensure a clear exit for extra hot or pressurized water. If homeowners do not test their valves, it’s possible for a water heater to become too pressurized, have no place to put that pressurized water, and explode.