Hi George:

Thanks for reply.

I have an expansion tank on my hot water heating system, =but to the best of
my knowledge i don't see any for the hot water system (the cylindrical hot
water heating system).

House is 30 yrs old.
Just replaced the hot water heater, but nobody ever said anything about an
expansion tank for it . Should there be ?

What types are used for this purpose ?
I don't think I've ever seen one for the hot water system ?

Not to sharp with this stuff; the feed water is of course common to both
systems; does the one expansion tank on what I take to be (only) for the
heating system help the hot water system in this regard ?

Bob

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"George" wrote in message
...
Robert11 wrote:
Hello:

Never had the opportunity to look inside one, but as we just had a new
wter heater installed, I became curious. It's the typical upright
cylindrical kind, gas fired.

Was wondering:

Is the unit designed to keep a certain water level always in the tank, or
is it designed to trap an air bubble at the top ? There isn't any float
regulator inside, to the best of my knowledge.
How does this work ?

The tank is completely filled with water at service pressure and there is
no air cushion.

If it truly fills totally with water, isn't the internal water pressure,
with no elastiucity, a problem ?


Yes, that is why an expansion means is specified and usually required for
most homes.


How do they maintain such a good (hopefully) seal at the top of the tank
?
I imagine that the tank is fabricated from rolled steel, with a top and
bottom fastened on somehow. How is this done and sealed ?

Any pix on the web showing internal construction ?
Couldn't find any.

Thanks,
Bob