Do I need an expansion tank?

I think people started needing expansion tanks on water heaters when muncipal water supplies added check valves to stop contanimation of the water system. Since you don't have a check valve to prevent backflow, I don't see why you would need one.

Don't you think his water system has a check valve?

It probably has at least one at the well, but if he has a bladder tank between the hot water tank and the well, that should allow for all the expansion necessary.

He indeed doesn't need one, but that's not the reason.

He doesn't need one because the pressure tank for the well serves the same purpose.

Trust the plumber.

You don't need one for the domestic hot water because the pressure tank for the well will accomodate any expansion from the water heater.

You *do* need one for the boiler, even though you have a well, because there's a check valve between the boiler and the pressure tank. You may not be aware that you have a check valve, but you do: the pressure reducing fill valve at the boiler is a one-way valve, to prevent the possibilty of contaminating the potable water supply with a backflow from the heating system (e.g. in the event of a catastrophic loss of pressure in the potable supply).

There is no existing check valve between the bladder tank and the indirect water heater domestic intake. You confirmed my suspicion that the house bladder tank acts as an expansion tank for the domestic water system.

Thank you all very much for your comments.

I don't know of many that do. Mine certainly does not. Not in my last house either. Or the one before that. Why do you think he has one?

Backflow preventers are relatively new in residential applications also. I have four in my commercial/industrial buildings, none in residential.

Perhaps because he is on a well and I have never seen or heard of a well system without one. The footvalve _is_ a checkvalve and if it is a submersible, the checkvalve is built in. If there wasn't one, the pressure tank would empty back into the well every time the pump shut off.

Harry K

:-)

The check valve in a well system would be between the punp and the bladder tank. Not the bladder tank and house water pipes. So he doesn't need an expansion tank for the water heater.

Or if you shut the water off to make repairs...

I believe that was explained earlier.

Harry K