You have a potential bomb in your house. No, we’re not talking about natural gas or propane. That seemingly innocent cylinder in your basement or utility room known as the hot water heater can turn lethal.
What? It simply heats up water; how can it be dangerous? Well, in the vast majority of cases it isn’t; safety devices built in to water heaters mean they operate perfectly nearly all the time. But a combined failure of two devices in the tank can cause a build-up of steam which can turn the heater into a bomb, with a blast big enough to destroy your house.
If the temperature-pressure relief valve (T&P valve) gets clogged or stuck, excess steam can’t escape. If the thermostat subsequently failed, causing your tank to overheat, the water would continue to expand without relief from the valve. Eventually, the increased pressure would rip the tank apart in an explosion of steam and metal.
A crew of “radical” plumbers did a test on a brand new water heater awhile back, plugging the valve and setting it so the thermostat was stuck “on”. The small, 12-gallon tank exploded, shooting more than 40 feet in the air and flying 400 feet before it landed. You can see it here.
You should test your T&P valve once a year. Pull up or push down on the valve handle, and check to see that hot water should come out of the overflow pipe. If it does, the valve is working properly. (Remember, the water’s hot, so be careful!)
If you’ve noticed sputtering or spewing from your hot or cold taps; found that your hot water is too hot, even though you’ve set it to a moderate temperature; or noticed regular dripping from your T&P valve, the tank might be overheating, and you should get your thermostat looked at or replaced.