Derald wrote:
"David Hare-Scott" wrote:

How on earth could that much pressure develop and from what? How
does this back pressure get through a closed tap or force its way in
past an open tap? Makes no sense.


In general, a system as proposed by Higgs Boson should have a
backflow preventer, sometimes known as an anti-syphon valve. The
building codes in California (where Higgs and I both live) require
it.


Weird. What a waste of money.
I think someone misunderstands antisiphon fittings. In the event
of loss of system pressure or the occurance of "negative"
differential, antisiphon valves open the system to the atmosphere to
reduce the possibility of introducing pollutants from downstream. In
many local jurisdictions across US, they are required on at least
exterior faucets/hydrants/hose bibb fittings; on laundry and
dishwashing machines; and on those hand held "shower" things.

I wonder just how often the situation arrises where this gadget actually
does some good. Has it ever been observed? This protection is so vital
that the Sydney metropolitan area (over 4 million people) gets by without
them.

D