Really dangerous water heater failure (True Story)

[Nukedaddy]

I read and commented on the exploded heater element thread below and it reminded me of one of my personal combat stories. About 30 years ago
I went on a service call for a home that had been subject to a near lightning strike. Electricians had already been there for a couple of hours replacing the meter and some breakers. The water heater was a plain-jane Rheem 40 electric. There were smoke marks coming up from both element covers. I turned off the newly replaced breaker and tested the bottom element first. It was open (burned out) so I shut off the inlet valve, connected a hose to the drain and opened it to drain the tank. Water came flying out like the supply valve was wide open! So I went to shut off the main. While I was across the basement at the main stop I heard a POW and hiss! The drain hose had blown apart and live steam was shooting all about the basement!
How many times I have set down in front of a heater while it drained! If I had, my eggs would have been steam boiled!
Here is what happened: Apparently the heater was energized to the upper element when lightning struck. The high limit and the upper thermostat were welded shut by the surge before the breaker failed. The lower event blew as they are always energized on one side only. When the electricians restored power the heater started with no thermostat or high limit. By the time I got there there was a big steam bubble in the top of the heater. There was a double check on the meter. No expansion tank, just one of the ballcocks with a relief valve. And the kicker? The relief valve on the tank was pressure only, not temp and pressure.
close call!

 

[breplum]

Damn fine story.
Thanks for sharing.
check out plumbing zone.com where professional plumbers waste their off hours.

 

[Matt30]

Wow that’s a wild, scary story. Thanks for sharing.

 

[Twowaxhack]

I read and commented on the exploded heater element thread below and it reminded me of one of my personal combat stories. About 30 years ago
I went on a service call for a home that had been subject to a near lightning strike. Electricians had already been there for a couple of hours replacing the meter and some breakers. The water heater was a plain-jane Rheem 40 electric. There were smoke marks coming up from both element covers. I turned off the newly replaced breaker and tested the bottom element first. It was open (burned out) so I shut off the inlet valve, connected a hose to the drain and opened it to drain the tank. Water came flying out like the supply valve was wide open! So I went to shut off the main. While I was across the basement at the main stop I heard a POW and hiss! The drain hose had blown apart and live steam was shooting all about the basement!
How many times I have set down in front of a heater while it drained! If I had, my eggs would have been steam boiled!
Here is what happened: Apparently the heater was energized to the upper element when lightning struck. The high limit and the upper thermostat were welded shut by the surge before the breaker failed. The lower event blew as they are always energized on one side only. When the electricians restored power the heater started with no thermostat or high limit. By the time I got there there was a big steam bubble in the top of the heater. There was a double check on the meter. No expansion tank, just one of the ballcocks with a relief valve. And the kicker? The relief valve on the tank was pressure only, not temp and pressure.
close call!

Temp doesn’t make them explode, the pressure does. There is a relationship between the two.

The temp does convert the water to steam but it takes pressure to make it explode. The tank ruptures from the pressure, the pressure drops to atmospheric pressure at the rupture point and the superheated water converts to steam. BOOM


That’s why a pressure cooker doesn’t explode. It’s not closed, it has a pressure relief valve, not a temp relief valve.

With a pressure relief valve and a relief valve on the toilet ballcock the system couldn’t build excessive/dangerous pressure, If those two valves where operating correctly.
You should’ve had steam shooting out of the toilet. If that failed and the pressure built the pressure relief valve should’ve acted.

So you had two safety systems still in place. Not ideal but that just goes to show you it takes a very special situation to make one go boom.

An expansion tank would’ve increased the possibility of at least a small explosion. The toilet relief discharges water, the expansion tank doesn’t. We want the system to relieve itself in a runaway heat situation

Thanks for sharing.

 

[FishScreener]

Temp doesn’t make them explode, the pressure does. There is a relationship between the two.

The temp does convert the water to steam but it takes pressure to make it explode. The tank ruptures from the pressure, the pressure drops to atmospheric pressure at the rupture point and the superheated water converts to steam. BOOM


That’s why a pressure cooker doesn’t explode. It’s not closed, it has a pressure relief valve, not a temp relief valve.

With a pressure relief valve and a relief valve on the toilet ballcock the system couldn’t build excessive/dangerous pressure, If those two valves where operating correctly.
You should’ve had steam shooting out of the toilet. If that failed and the pressure built the pressure relief valve should’ve acted.

So you had two safety systems still in place. Not ideal but that just goes to show you it takes a very special situation to make one go boom.

An expansion tank would’ve increased the possibility of at least a small explosion. The toilet relief discharges water, the expansion tank doesn’t. We want the system to relieve itself in a runaway heat situation

Thanks for sharing.

Yes but if you put too many beans in the pressure cooker, they can clog the vent to the jiggler, and when the pressure gets high enough to blow out the relief plug, it will spray beans all over the kitchen, and make a terrible mess. Don’t ask how I know.

 

[Hamberg]

...they can clog the vent to the jiggler...

I'm realizing, as I get older, my Jiggler is clogging more and more.

 

[Twowaxhack]

I'm realizing, as I get older, my Jiggler is clogging more and more.

You need a young “ housekeeper “ to keep it clean.

 

[Hamberg]

You need a young “ housekeeper “ to keep it clean.

YES, YES - I do!!!!!

 

[Nukedaddy]

Temp doesn’t make them explode, the pressure does. There is a relationship between the two.

The temp does convert the water to steam but it takes pressure to make it explode. The tank ruptures from the pressure, the pressure drops to atmospheric pressure at the rupture point and the superheated water converts to steam. BOOM


That’s why a pressure cooker doesn’t explode. It’s not closed, it has a pressure relief valve, not a temp relief valve.

With a pressure relief valve and a relief valve on the toilet ballcock the system couldn’t build excessive/dangerous pressure, If those two valves where operating correctly.
You should’ve had steam shooting out of the toilet. If that failed and the pressure built the pressure relief valve should’ve acted.

So you had two safety systems still in place. Not ideal but that just goes to show you it takes a very special situation to make one go boom.

An expansion tank would’ve increased the possibility of at least a small explosion. The toilet relief discharges water, the expansion tank doesn’t. We want the system to relieve itself in a runaway heat situation

Thanks for sharing.

The “POW” was the drain hose blowing off the threaded crimped on hose end. I imagine the hose, even the heavy commercial type I was using, was not rated for the steam temperature at 80 to 125 psi saturated steam. If I remember my steam tables 125 psi steam is over 300F.