I've a new oil-fired boiler with an indirect water heater. The
loop has an expansion tank. The domestic hot water does not. I have
well water (bladder tank located 50+ft away from the boiler).
Do I need an expansion tank on my domestic hot water? The plumber who
installed said I don't need one, but I'm concerned.
All comments appreciated.
Anthony M. Falcone
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.
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
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.
Yes & in some areas, backflow prevention is handled only at hose bibs
& dishwashers via individual devices.
My neighbor had a city permitted / inspected re-pipe & now has vacuum
breakers at the hose bibs.............no check valve & thus no need
for an expansion tank.
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
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).
Doug Miller (alphageek at milmac dot com)
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