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Hot water heater

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Jeff Handy

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That is called a doohickie.

Actually, that is an expansion tank.
It is half filled with air contained in a plastic bladder, and it gives water somewhere to expand into when it gets hot.

Otherwise the temperature and pressure relief valve on the heater might have to activate to release some water to reduce pressure.
 

Jeff Handy

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There also should be a strap around it, to add support from the ceiling, or sidewall somehow.
Too much weight hanging loose like that, although it is commonly done (wrong) like that.
 

bud16415

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Just poking fun here.:fun:



Some areas of the country use the term Hot Water Heaters I grew up saying it in fact we also call soda, pop.



I think it is a combination of the other two usages, Hot Water Tank and Water Heater.



Things changed around here as if I go in asking for a Hot Water Heater the guy tells me we are all out we only have Cold Water Heaters left.

Jeff is correct it is an expansion tank and no one I know has one around here. That makes me wonder where the expansion goes if not out the pressure valve. My guess is it pushes back on the cold water coming in.
 

Jeff Handy

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I think expansion tanks are only needed if there is a device on the incoming line that prevents expansion pushing back into the city supply, towards the street.

Like a PRV or a backflow preventer where the supply enters the house.

Other codes might require them for other reasons.
 

havasu

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It's also considered a cold water heater, right?
 

Jeff Handy

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I have raised this point on here several times.

“Hot water heater” is wrong, you don’t need to heat water that is already hot.

I tell my clients the same thing, but most will not admit defeat.

The only water heater that could be called a “hot water heater” would be one that you bought off the back of a truck, which you knew had been stolen from somewhere.

Cold water heater makes more sense, but not necessary.
 

havasu

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Sounds like the old "clip" vs. "magazine" references on gun forums. To the OP, call it what you want.
 

Eddie_T

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Interestingly, I had dinner with a friend last evening and noticed a small blue tank mounted vertically on top of his gas WH and asked what it was. He didn't know so I took a closer look. The label said expansion tank and it had a shrader valve indicating a bladder. It was my well pressure tank in miniature. I have never seen them on electric WHs.
 

Sparky617

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When water heats it expands. Fun fact about water, it also expands when it freezes. Hence the dangers of frozen water pipes.

If you don't have a backflow prevention (BFP) device on your water meter you don't need a expansion tank. My town is adding backflow prevention devices at our meters so expansion tanks are required. When the water expands without a BFP the water expands back through the meter into the water main. If you're on a well it would expand back into the pressure tank. If you have a BFP the expanding water needs a place to go or it will come out the TPV on the water heater. BFPs prevent contaminated water from your house going into the mains.
 

68bucks

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Semantics are funny. I correct people when they tell me they had to unthaw a frozen pipe or unthaw a frozen steak for dinner. If you unthaw it you are freezing it. I always get a weird look until they think about it.
 

bud16415

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Semantics are funny. I correct people when they tell me they had to unthaw a frozen pipe or unthaw a frozen steak for dinner. If you unthaw it you are freezing it. I always get a weird look until they think about it.
My dad used to tell me to turn on the dark switch when he wanted the lights off.
 

Skeezix

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House pressure 70 PSI, backflow preventer valve installed.

When the expansion tank on my water heater finally died, I could tell that something was wrong. When I turned on any hot water tap, the water would gush out for a second, then flow normally. After I replaced the expansion tank, the water didn't gush out any more.
 
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