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I am moving my 80 gal water tank to a better location in my basement to give shorter hot water plumbing runs and be next to my furnace.

The old expansion tank was installed in "series" with the tank at the end of a plumbing run:

HWT = HOT WATER TANK
OP = OTHER PLUMBING
EXP = EXPANSION TANK
CWM = COLD WATER MAIN

 CWM --- OP ---  EXP --- HWT

In the HWT's new location it would be more convenient for me to install them like this:

 CWM --- OP ----------------- OP -----
                |       |
               EXP     HWT

Is the above a satisfactory install? Or would the below design better isolate the HWT pressure variance?

 CWM --- OP ------------- OP -----
                  |
             EXP---
                  |
             HWT---

Put another way - does it matter where in the cold-water-system the Expansion Tank is installed? For example, could I just put it next to the Main without any regard for where the hot water tank is located?

  • It does seem like in either of your proposed installs, the expansion tank would serve its function of absorbing thermal expansion. The seem almost equivalent, except in one case you have water for other uses flowing past the expansion tank tee. So I think this is really a question of how specific the plumbing codes are on the placement of the expansion tank. I don't know that answer. – Shimon Rura Mar 13 '17 at 15:35
  • Doesn't really make a difference. The expansion tank doesn't relieve pressure in the water heater, it relieves pressure in the plumbing caused by the water heater. Best bet is search for the manual for your expansion tank and see what it says about preferred installation. – OrganicLawnDIY Mar 13 '17 at 15:42

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