Expansion tank necessary?

[Adkroot]

Recently installed an AO Smith GDV 40lp water heater. Water system is a private well and since I have a pressure tank I didn’t install an expansion tank. When I leave for an overnight or more I shut off my main to err on the side of caution, but I got to thinking that this would isolate the heater from the pressure tank and its function as an expansion tank for the heater.
Is this a concern, and aside from leaving the main shutoff open, it is enough of a concern that it might be worth considering installing an expansion tank?
Thanks, Dan

 

[Fitter30]

Your bladder well tank is doing the same job as same expansion made for city water.

 

[Sponsor]

 

[wwhitney]

Your bladder well tank is doing the same job as same expansion made for city water.

Right, but when there is a closed valve between the bladder well tank and the water heater, and the water heater is left running, the bladder well tank can't do that job.

So for the OP, if the above describes the scenario you have, then yes there's a potential problem. I suggest either (a) skip turning off the main valve for short absences (b) turn off the water heater when you turn off the main valve or (c) install an expansion tank.

Or at least, if you confirm that your water heater has a functioning T&P valve, you could put a small tray under the outlet and monitor it to see if you are getting any discharges. I guess if you are shutting off the main valve when the water heater is quiescent (versus while it is actively heating after a long hot water draw), then it may be that the expansion/contraction cycle of the water heater cooling off slightly and then reheating is not a big enough magnitude to be a problem.

Cheers, Wayne

 

[Reach4]

Another option would be to turn off the power to the pump, rather than closing the valve. A broken hose could let the water stored in the pressure tank out, however.

Or close the valve, and turn the water heater to vacation or off.

 

[Adkroot]

I guess part of my question is if when in vacation mode there’s little to no concern about expansion.

 

[Fitter30]

There's no concern.

 

[Jackyu051]

Shutting off the main water supply isolates your water heater from the pressure tank, which can lead to excessive pressure buildup due to thermal expansion.

Installing an expansion tank is the best solution to prevent damage and ensure safety. It is affordable and reliable and protects your system during shutdowns.

If you choose not to install one, leaving the main shutoff open can help, but it is less effective. Contact a plumber for proper installation.

 

[Fitter30]

Shutting off the main water supply isolates your water heater from the pressure tank, which can lead to excessive pressure buildup due to thermal expansion.

Installing an expansion tank is the best solution to prevent damage and ensure safety. It is affordable and reliable and protects your system during shutdowns.

If you choose not to install one, leaving the main shutoff open can help, but it is less effective. Contact a plumber for proper installation.

Newer water meters and some pressure reducing valves have a check built into them. Ex tank is not a option it's necessary. Air pressure in tank bladder needs to match incoming water pressure.

 

[Bannerman]

Your well pump pressure tank, will act as a WH expansion tank, however, you are correct about the main shutoff valve isolating the WH from the pressure tank.

To prevent weeping from the WH's pressure relief valve, you could either install an expansion tank plumbed directly to the supply line of the WH, or as R4 suggested, shut the power off to the pump and keep the main valve open.

If you plan on also shutting off the WH, the inverse of water expansion may occur. If the water within the WH becomes cooler, the water will contract so best to not isolate the WH from either an expansion tank or the pressure tank as either tank should maintain some positive pressure in the WH. If the WH is subjected to a vacuum, it could collapse inward as the tank is designed to withstand positive pressure, but has limited tolerance to a vacuum.