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Tanklets > Water Heater Won't Shut Off

Q: My mother has an AO Smith model FPSE 50 236 gas water heater. The problem is it will not stop heating. The burner runs constantly. She has to shut it off or her gas bill doubles and then she has to remember to turn it back on again a half hour before she wants to shower. Since she is on a fixed income, she asked me to fix this. Does anyone have an idea what the problem might be? Thermocoupler? Thermostat? -- Big Dummy in Michigan

A: A burner that won't shut off is BIG TROUBLE that needs to be dealt with immediately. There is a very real risk of an explosion. Either the control is malfunctioning or there is a good sized hot water leak that's forcing the tank to keep firing. Start by shutting off the gas. Make sure no water in the house is running and go check the water meter to see if it's turning. If it is still, than it must be a problem with the gas control. Have it replaced and have the relief valve checked/replaced at the same time! A heater blowing up has the power to level a modest home... Act quickly! -- Larry (10/14/05)

Q: Our water heater is @ 10 yrs old and came with the house when we purchased it 3 years ago. The past few weeks we have to turn the water in the shower much hotter to get the same comfortable heat setting we had before. We originally thought this was because of the cold winter here in CA (don't laugh!). But, it has gotten worse in the past 2-3 days, we have the setting almost all the way to the hottest setting. AND, today, we were out of the house from 12-7. When we arrived home, the water heater was 'on'... it sounded like it was still heating up water. It is now @9:45 pm and it's been on ever since we got home - almost 3 hours that we know of. What is going on? Gas leak? Something fixable? Needs to be replaced?

A: First of all, shut the water heater off by turning the control to "off." Frankly, since I'm answering this a couple of hours after you posted, I hope you're still alive to read it. What you're describing is very, very dangerous. Water heaters that won't shut off sometimes explode and it's usually catastrophic. Like a rocket launch with your house (and maybe you) in the path of the rocket.

The first thing you described sounds like a failing dip tube. There are lots of posts on The Tank about that. Your tank sounds as if it's old enough to have been made during the time when such tubes were being made from a plastic that disintegrated under certain conditions. If you have also noticed clogged aerators, that's another sign.

But refusing to shut down is something different, a failure of the control, or possibly a leak in the plumbing. If it's the latter, there is a post just a few down from this one by somebody with logon JABRON that will help you find the leak. If it's the control, though, you should maybe consider a new water heater.

Replacing a control is expensive and considering the age of your tank, replacement of the whole shebang might be more economical. Read up under Choosing a water heater, if you take that route, so you can make an informed choice. Good luck! -- Randy (1/24/05)