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Posted by on March 29, 2007, 8:13 am
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.
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