Two water heaters, new whole house filter, max 90 psi, can I use one Expansion tank?

[Ed P]

Two water heaters, one house, other for detached garage washing machine. Never had expansion tanks installed.

Re piped and added whole house water filter system with bi-pass. Max psi rating is 90 psi for water filter canisters.

City pressure 145 psi, regulator set at 65 to 70 psi. (measured)

Each water heater can take closed house/garage system to 140 psi (measured).

Can I install a single very large Expansion tank anywhere in the cold water loop to cover both water heaters? Or must I have large individuals closely to each water heater?


Since each water heater is 40 to 60 gallons and max press needs to be at or less than 90 psi, individual expansion tanks are going to be 10 gallon (water volume, actual tank volume about 2 times that). Heafty size for installation locations.

 

[Reach4]

You can have a single expansion tank as long as neither water heater is separated from the expansion tank by a checkvalve or a regular valve that might be closed. That probably means you need two expansion tanks.

 

[Sponsor]

 

[Ed P]

No check valves but of course there are isolation valves at each of the two water heaters. Joy to do both. Thanks for quick response.

 

[Reach4]

Thinking about it, I guess those valves would only be closed when the associate water heater is off. So with that in mind, I now think one tank would do it.

Not a pro.

 

[Terry]

A properly sized expansion tank works for system. They don't need to be at the water heater location, just within the system.
Any check valve would take it out of the system. Sometimes when water heaters have recirc lines, they also have checks.