By Darrell Hay

Q: I live in a ground-floor condo built in the 1960s. I got burned in the shower. Yes, I have taken showers before and do know how to operate the controls correctly! But the water has never been this hot. It literally felt like boiling water.

The electric tank is only 30 gallons and rests beneath the kitchen counters in a corner right behind the shower wall. I saw a little bit of hot water here on the kitchen floor earlier. But now no leakage, and the area around the tank is completely dry. I have to set the taps on full cold in order to have water cool enough to wash my hands. I didn’t change the thermostat setting; it is resting right on 125 degrees. Obviously, the water is hotter than 125.

A: Almost all electric water heaters have an upper and lower heating element. Each has separate thermostats, and a high-limit switch to protect against a failure of either. Remove the second outer access cover — after you turn off all electric power to the tank — and you will see another thermostat. The problem is one of your thermostats has failed, and additionally your high-limit switch has failed.

Another possibility is that the upper thermostat is not securely resting against the tank wall, where it measures heat and houses the high limit. As a result, one or more heating element(s) is stuck on, boiling the water.

The water you saw on the floor was the relief valve dumping overboard to prevent the tank from exploding. Yes, that’s right — tanks can and do literally explode when you have runaway thermostats or a failed high-limit switch, and when the relief valve fails or is blocked.

Thankfully, that is very rare and takes several consecutive failures (you have two of three!).

In Burien a few years back, an exploding tank blew the walls and roof off a concrete block building in a strip mall. It rocketed through the roof and landed across Highway 99, some 600 feet away in a restaurant parking lot. Fortunately, no one was in the building at the time.

The relief valve lets water and steam pass if the temperature exceeds 210 degrees, or the pressure exceeds 150 psi. It is literally a lifesaving device. In newer buildings, the relief valve is drained to the exterior, rather than dumping on the floor as you experienced.

If you are feeling handy and very comfortable with electrical equipment, you can fix this relatively cheaply. If you have any doubt, call a plumber or electrician, because this is not simple fix, or particularly forgiving of mistakes.

Turn the power off, and verify it is off. You will need two new thermostats, sold separately as upper and lower, with the high limit integral to the upper. Likely they will not have the brand available specifically for your tank, but that is acceptable, as the provided wiring diagrams will let you retrofit a generic thermostat to almost all applications. Expect to pay $15 or so each.

The color-coded wires will need to be marked, traced and made to connect to the new thermostats as the directions indicate. Be sure the thermostats are snug against the tank wall when you are done.

Darrell Hay is a local home inspector and manages several rental properties. Send home-maintenance questions to dhay@seattletimes.com. Sorry, no personal replies.

source : seattletimes.nwsource.com