When Do Water Heaters Become Bombs?
Water heaters have become a common luxury which we take for granted. How many of us give it second thought when we're enjoying our bath or shower, giving our dishwashers the power to clean the dinner dishes, or choosing between hot, warm, and cold cycles. We don't think about this "Worry Free" appliance any more than we think about the destroyed homes, the water tanks shooting through the roof like a rocket, or the lives which have been lost. Yes, your water heater is much safer than those of the past. But how safe is it? Most people would be surprised to learn that the possibility of a water tank explosion still exists.
Water expands when heated and is capable of tremendous pressures. This is called "Thermal Expansion". Even the most modern water heaters cannot defy the laws of nature, so what keeps them from exploding at the rate they did in the past. Most water heaters are only equipped with one or two safety devices, and these devices do fail.
Water heaters us thermostats to regulate the temperature of the water. These thermostats do fail. If we're lucky, they will fail in the off position and there will be no hot water. Unfortunately, they also fail in on position. I have seen this myself when called to repair water heaters. Not all water heaters are equipped with a high limit switch and the circuit to the heating elements remains open. This means that the water will be over heated and pressure will exceed the limit of the water tank. The only things preventing an explosion are the safety devices.
At minimum, your water heater will be equipped with a T&P (Temperature & Pressure) valve. This valve is designed to open
when the pressure, in the tank, exceeds a safe limit (150 PSI). The water pressure is then diverted to a safe location. Another safety system is an overflow tank. This tank receives the extra, pressurized, water then pushes it back into the main tank when pressures return to normal levels. However, most water heaters are not equipped with this tank. Believe it or not, the only safety device is, in many cases, the T&P valve. Unfortunately, the T&P valve can also fail. What happens when the thermostat and the T&P valve fail at the same time? Does this happen? Yes, it does.
Thermostats do fail in "on" position and T&P valves refuse to open, so what happens in this case? There is one other fail safe.
Normally, the water pressure in the water supply line is low enough to give the over pressurized water a place to expand. This supply line is connected to the same water lines that are supplying water to the home, or other building. In other words,
the pressure backs up into the city water supply. However, pressure reducing, or check valves could prevent this. In this
case an explosion could occur. Several things must happen at once to cause a water heater explosion. Unfortunately, these explosions still occur today. Take steps to make sure you, and your family are safe.
Test the T&P valve quarterly. Insure that there are no pressure reducing/check valves on the water heater or main water supply line. Check for additional safety devices such as a expansion tank.
Learn more about water heater inspection and testing from Michael Swift at www.handyman-dallas.com
I recommend a thorough inspection of your water heater and annual testing of the T&P valve. You can do this yourself, or hire a professional.
About the Author: Michael Swift is a professional handyman working in home repairs and remodeling. Learn about home repair and remodeling yourself at www.handyman-dallas.com