Expansion tank

(For residential water heater) Does it matter where you put the expansion tank in the system? I am thinking anywhere upstream of the water heater is ok. Correct me if that's not the case.
I'm planning on sweating a brass T to connect the tank to. Is there a better way? Would it be better to have a ball valve before the tank? WH is piped with 1/2" copper.
Thanks, Paul
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PB wrote:

IMO it makes no difference as long as it's on the house side of any check valves or water pressure reducing valves which prevent expanding water from escaping back to the city main. Convention usually puts them on the "hot" side, but I think that's just a holdover from how it's done for hydronic heating systems ("forced hot water") where there's a pressure reducing valve feeding water to the boiler, and the expansion tank /has/ to be there to do its job.
The water heater provides a through connection between the hot and cold water lines in the building, so pressure will be the same throughout all that plumbing, excepting "altitude" presure differences, which will only amount to 15 psi or so in a three story house.
But for a two story house...
Scene: Divorce court
Judge: "Well sir, and why do you seek a divorce from your wife of 30 years?"
Plaintiff: "Your honor, for the past twenty years we've been living in a two story house"
Judge: "And why should that make you want to divorce your wife?"
Plaintiff: Your honor, the two stories are, "I've got a headache" and "It's that time of the month."
Drum roll and rim shot......
Jeff
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Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
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Some water heaters have or have added check valves, If this is the case then would need to be on the hot side but if not install on the cold side.

years?"
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MC wrote:

What is the purpose of using a tight sealing check valve on a water heater? I'm always interested in learning something new.
Iknow about "heat trap" nipples used on water heaters to prevent thermosyphoning heat losses, but I wasn't aware that they sealed completely in the "reverse direction".
Jeff
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Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"As long as there are exams in public schools there will be prayer in
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I have only seen them in use, never had them on any of mine so far. After reading a water heater owners manual that used them I had though they did seal, maybe not.

then
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I've never put expansion tanks on the hot side, boilers or WH's.
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HeatMan wrote:

As long as "cold side" means between the boiler feedwater pressure regulator and the boiler itself, putting it on the "cold side" is perfectly ok.
Jeff
Jeff Wisnia (W1BSV + Brass Rat '57 EE)
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Jeff Wisnia wrote:

Put on the cold side. When I moved in, my HWH had one on the hot side & every time you turned on the cold water the expansion tank pushed hot water thru the cold pipe until the pressure in the expansion tank equalized. I had to let the water run for a minute or two before it got cold enough to drink. Annoying!
MikeB
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