Water Expansion Tank?

[Dave]

Installing an electric water heater at the cabin. New plumbing.

Was just going to T a line up from the pressure tank (including a shutoff valve) and over to the water heater. Any need for an expansion tank?

Thanks

[nobody05]

No any thermal expansion will push back into the pressure tank.

[Dave]

So, that's not harmful to the pressure tank?

[delcecchi]

Uh, just a second. Normally there is a valve or some sort of automatic thing to keep the heating water separated from the drinking water. I am pretty sure you don't want heating water going back into the drinking water supply.

So you will need the thermal expansion tank, I think. If the tank or the city water was enough and no valve was required then no one would need the air tank, and they put them in.

Check the rules, but I bet you need one.

[OLE77]

I have never seen an expansion tank on a domestic hot water heater. The cold water goes in the bottom of the heater and as it is heated hotter water rises to top of tank were it goes out to your DOMESTIC hot water lines were it is perfectly safe.

[Archerysniper]

I have never seen an expansion tank on a domestic hot water heater. The cold water goes in the bottom of the heater and as it is heated hotter water rises to top of tank were it goes out to your DOMESTIC hot water lines were it is perfectly safe.

Almost all commercial heaters will have them. And while purchassing them make sure they are for potable water and not hydronic heating.

[Whoaru99]

What's the point of the expansion tank and how does that relate to the hot water vs rest of the water? Granted, I'd not want to be drinking hot water but it's all the same, common water at some point coming into the house.

[Dave]

Just spoke to some family and friends who have a well and hot water heaters (residential homes and cabins) and nobody has any expansion tank on their systems. Non of them have never seen one on a system either.

[delcecchi]

Duh. If it is a water heater, it doesn't need an expansion tank. Somehow I got it in my mind that this was for hot water heat, as in radiators etc. That would need expansion tank.

Never mind.

[nobody05]

Some instances you do need a expansion tank on your domestic heater. For instance when your supply has a backflow preventer or such. Water heats up and it needs a place to expand. With out one on a system such as one with a back flow preventer coming from your source you will decrease the life of your heater due to thermal expansion. They are tiny about the size of gallon of beans can with bladder inside.

[WallEYES]

In your situation you do not need a expansion tank unless you have a check valve upstream of the heater...this will not allow thermal expansion and your temperature/pressure relief valve will trip at the water heater...the expansion tank will make up for this.

[MNice]

In your situation you do not need a expansion tank unless you have a check valve upstream of the heater...this will not allow thermal expansion and your temperature/pressure relief valve will trip at the water heater...the expansion tank will make up for this.

Ya, what he said. In an open system, no x-tank is needed.

[Dave]

Ahhhhh, thank you, guys, for confirming I don't need one.

[Tom7227]

Not sure that I've read a thread in the home improvement section that had as much bad advice in it.

[MNice]

Please explain.

[delcecchi]

Yeah. Bad advice that a water heater doesn't need an expansion tank?

[Tom7227]

Well the responses went back and forth, yes and no, and it just seemed to me that it was very confusing.

[delcecchi]

Yeah, sorry for any confusion I caused by my thinking hot water heat, not water heater. My bad.