Originally Posted by Reno


A residential water heater does not have an "air control valve" unless it has been added.. And then, I'm not sure why they would because I've never seen it. If you have a bad thermostat or an element that has shorted out, over heating won't be a problem.. Actually, it'll he right the opposite since it has "shorted out" it won't be heating at all. A thermostat that is over juicing an element, it will pop the element if it doesn't trip the internal breaker on the thermostat first.. In 99.9% of cases



Reno Bud, I'm not sure why you want to be so argumentative about something that you obviously don't know as much about as you think you do. And by the way, I never said a water heater had an air control valve, although it does have a pressure relief valve.

Initially, when he first asked the question he didn't give us all the details and I suggested before I knew that he was on city water that if he had a well the WATER TANK air control valve might be bad. It can cause a similar condition, but it will be on both hot and cold. This is obviously not the problem.

And yes, a bad element can cause the water to overheat. There are a couple of conditions with a bad element. It can be open, and in this condition, it will not heat at all. It can be grounded or "shorted to ground" as some might say, in this condition with some water heaters it will heat all the time. I'm sure you understand electricity too so I won't go into a detailed explanation as to how this works.

And again, a bad thermostat, one that fails to cut off and stays engaged will cause the water to heat all the time as well. It seems that you are under the impression that the element will not heat up over 140, but this is not true. It will continue to heat higher than 140 if it is grounded out until it eventually burns in two and goes open. The same thing applies to a thermostat that fails to shut off, the element will continue to heat unless the element goes open, the thermostat eventually cuts off, or a breaker trips (which in many cases doesn't happen).

And both of these types of conditions can happen without tripping the breaker. As a matter of fact, a grounded element can be a very dangerous condition, especially if it happens in an older mobile home that had all metal siding.

You may never have heard of an overheating HW heater but it does happen and it causes the exact same type of problem that he is describing in this thread other than the low pressure in the one faucet which is most likely stopped up.

This is my last post on the matter, if the OP would like any of my assistance troubleshooting this issue he is welcome to PM me.

Last edited by westflgator; 05/02/18 03:47 PM.
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