On Mar 29, 5:13 am, wrote:
On Mar 29, 5:46 am, "Joseph Meehan"
wrote:



BobK207 wrote:
Adding a back flow preventer or a check valve to a domestic water
supply will create a closed system.

Usually the issue of thermal expansion in a close system is handled by
installing an expansion tank on the cold water side of the water
heater.

Could the thermal expansion in the system be handled by installing a
pressure relief valve; with a relief pressure lower than the relief
pressure of the T/PO valve of the water heater?

Of course this relief valve would dump a small amount of water every
day...... approx the amount of expansion of the cold water heated to
water heater temp.

Is the expansion tank solution "better" than the relief valve
solution? or is a relief valve a better solution?

I'm just curious........... since I can see if the relief valve is
working but the behavior of the expansion tank is internal & thus
hidden.....so I have to go on faith as to whether the expansion tank
is doing it's job.

cheers
Bob

The standard solution is the expansion tank. I would guess that the TP
relief valve is for emergency use and is likely to fail after too many uses.
Water heater manufacturers tend to use real cheap junk on them. In addition
you are loosing the warning that the system gives you anytime the TP valve
goes indication something that should not be happening but making it as
usual event.

--
Joseph Meehan

Dia 's Muire duit- Hide quoted text -

- Show quoted text -

In theory, a relief valve set at an appropriate pressure would work.
However, you then have have 3 problems. You now have to deal with
sending the released water somewhere. It wastes water. And the
valve could eventually fail to close completely. An expansion tank
is the better solution, which is why it's used.

Released water goes into flower bed, actually caught in watering can
for watering container grown herbs.

According to my calcs, worst case water release would be ~1 oz per
gallon of hot water used (60F to 130F) most likely less since other
water uses would relieve pressure

Don't expansion tanks eventually fail as well? Anyone have an idea of
their expected life?

cheers
Bob