On Monday, November 23, 2015 at 10:05:24 PM UTC-5, Doug Miller wrote:
Don Y wrote in :

On 11/22/2015 11:51 AM, Doug Miller wrote:
Don Y wrote in :

On 11/22/2015 7:06 AM, Doug Miller wrote:
Don Y wrote in :

On 11/21/2015 5:20 PM, Doug Miller wrote:
Don Y wrote in news:n2qc5h$41c$1@dont-
email.me:

On 11/21/2015 10:55 AM, Doug Miller wrote:
Micky wrote in
news:n3605btdvs9avi246kpt1j8vvfrfptkeas@
4ax.com:

How did we get along without these tanks for so many years?

Because for many years, municipalities allowed the sort of behavior described
by
Don
Y -- if
the pressure in the residential system rises above the supply pressure, water will
be
forced
out of the residence and into the supply.

This is now prohibited in many locations, and homes are required to have
backflow
preventers to insure that this cannot happen.

Heated water has to expand somewhere, and if it can't expand into the municipal
supply,
you'd better have an expansion tank.

You can find lots of videos "exploding water heaters". There's a lot
of pent-up pressure in those systems and the heater is often the weakest
link.

And that has absolutely nothing to do with expansion tanks. Water heaters explode
due
to a
combination of runaway heating *and* a failed temperature-pressure relief valve. If
*that*
happens, no expansion tank is going to contain the enormous increase in pressure
that
precedes a catastrophic steam explosion.

Water heaters explode due to the fact that water EXPANDS when heated.

False. Water heaters explode due to the fact that water expands by several orders of
magnitude when it is BOILED. Simple thermal expansion of water due to heating in
normal
operation does not cause water heaters to explode.

Do you know how to boil water *without* HEATING it? (bring the tank into
the vacuum of space??)

Are you aware that water can be heated WITHOUT boiling it?

And, does it NOT expand??

Of course it expands -- but not nearly enough to cause an explosion, unless it boils.

Also, as I pointed out previously, water isn't the only thing that
expands when heated. The steel tank does too, increasing it's volume.