It's been a long time since I visited here, but I'm back with a question that's frustrating me.

I have a 20 gallon, 110v hot water heater. It has a single heating element. It was working fine until this weekend when Ira came through and we lost water for a couple days.

Now there is water coming out of the hot water faucet, but it's not hot. I disconnect the wires to the heating element and tested the element with an ohm meter. It showed continuity. I also tested the thermostat by checking to see that I get 110v across the wires and I do.

So if I'm supplying power to the unbroken element, how come there's no hot water?

Thanks,

Glenn

Here's an update. I have an identical water heater in another empty unit. When I checked on it, the water heater was full of air. The hot water faucet blew air for about 30 seconds before cold water started to come out. I assume the heating element fried when the water supply was cut.

But how does the water heater get empty? If there is no water supply to it, doesn't the water just sit in the tank? What displaces the water?

Hi Glenn...

I'm willing to bet that your water heaters don't have a VACUUM BREAKER... see image.

Here, especially when you mentioned the storm, IRA, I am quite sure that what happened is that somewhere within your town/city water system there was a backflow condition that occurred and siphoned the water out of the tanks and that in return allowed the thermostats to remain on and cause the elements to overheat and burn up.

If the vacuum breakers were present this would have prevented the siphonage as a vacuum breaker "breaks" the siphon by allowing air to enter into the system and that stops the water from getting sucked out of the heater.

This happens more than you might think in areas where vacuum breakers aren't installed. For example, when the fire department comes along and flushes the hydrants at full force, it can pull on the water in water heaters, boilers and, if someone has a hose in a pool, it can suck a pool dry... ;) On that note, say if a neighbor drops a hose into a pool that can in itself cause a back siphonage condition and that can suck a water heater dry, too.

Anyway, I'm pretty sure that is what happened here. Replace the elements and while you are at it, for $8.00 more each, I'd replace the single element thermostats, too as they were also stressed under these conditions. Best to replace all and just be done with this...

MARK

Very interesting. I'll replace the heating element.

Can you tell me how to determine if the element is bad? I thought that if the ohm meter toned, the element was OK?

Thanks,

Glenn

You confirmed power into the heater.

You confirmed power to the thermostat

DID you confirm power from the thermostat to the element? If power is going from the thermostat to the element, regardless of ohm reading the element must be bad.

I was thinking that the thermostats may have overheated/blown, but can't say for sure that is why I recommended replacing everything at this point. Clearly, even if one or two parts aren't bad at this point, they have been stressed and will go sooner than later.

Good luck!

MARK

PS: You may want to install vacuum breakers at the water heaters so this doesn't happen in the future... easy install and they are cheap insurance from this for the next storm.