The water company plans to install water meters in area of my summer cottage sometimes this winter. I assume that they will add anti-backflow device, so I will need an expansion tank this spring. The electric water heater is 50 gal so I expect to use a small tank. All plumbing is ½” copper and I am comfortable installing tank myself but the water heater is in attic so overhead space is limited. I imagine mounting tank vertically alongside of heater using a ½” T on cold supply to elbow to ¾” FIP adapter.

All pipes are drained each winter. If I mount with air valve up will tank drain to prevent freezing damage over winter?

Is ½” copper strong enough to support or should I add additional bracket?

Does it matter if valve is upstream or downstream of tank?

you can't assume they are adding a backflow device.
call them to confirm yes or no..

i would just remove the tank every winter. then you can put it in any position you want.

from the internet.. (also my humble opinion)

Search for: How far away can expansion tank be from water heater?
Where is the expansion tank normally located?
Image result for does it matter where a hot water expansion tank is mounted
Expansion tanks are normally installed above the water heater on the cold water line before it enters the water heater; however, they can really be installed anywhere on the cold water line prior to entry into the water heater.May 3, 2022

'tank' should be on CW side for the sake of the 'rubber' diaphragm which 'most likely' is not rated for hi-temps

There should NOT be a valve between the expandion tank and the WH


If, repeat IF, you are SURE there will be no valve between the tank and the WH then the tank may be located ANYWHERE on the CW piping leading to the WH.

Air UP with a full size 'side valve' for draining to break 'vacuum'.



[th.bing.com]

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.

Thanks.
I was assuming they were, but you're the second person who said check it out.

Thanks. Air side up makes sense to me and I appreciate your explanation of why it should be on cold side.

When I drain house in fall, I open everything up after shutting off street supply below frost line. After all pipes and water heater stop draining, I close them all, pressurize system with air and then let air escape through each faucet individually, starting from highest and working down until everything stops spitting on both hot and cold taps.

After that, I open everything back up, just in case, add use rv antifreeze in traps and toilet. So far so good over twenty years.

I am not sure what you mean by side valve by expansion tank. Can You elaborate?

Thanks again.

Mark V

good to go

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638