....
== Thanks blush NOT!

Damn good post, and I wonder what percentage of US homes
built in the
last 50 years have those air traps.
Dunno - all my experience is anecdotal and personal; not a
plumber by any means but a fair amount of home repair.
I know the codes for my nephews required them when he
built his house, located within three feet of every stand
pipe, which IS required by code.
Inside the last 50 years, we've lived in Coronado, CA and
Chicago IL, and they were required by code there.
Actually, the first time I came across them I thought
they were simply capped pipes that used to go somewhere but
got rerouted; they were the same ID as the supply pipes.
They were required in Chgo (northwest side), but don't
know whether it was a national or an urban code. I
re-plumbed an apt bldg. (6 units) and later our own home.
Our house was old (abt 100 yrs) and had them plus code
required them whether it was a repair or new construction.
That house even had pieces of actual lead pipe in it, and
the old gas pipes in the ceilings for gas lighting.
They had to be 1.5x the secondary supply ID and 24" min
length if I recall right (and I might not).
I suspect it's not a national code because it's not
required where we live now - I checked - did a bunch of
plumbing again - but only because we have well water, which
includes a large water tank which by design contains a large
amount of trapped air. A plumber friend, however, suggested
that I'd get a lot of backward movement in the pipes if I
relied solely on the well tank.
On the other hand, I've heard that they ARE required, and
I think it makes sense, because a water heater causes pipes
and water to expand/contract in such a manner as to burst
copper joints and especially plastic pipe, which is OK to
use in this area. There has to be somewhere for the water
to go if the hot water expands a bunch of pipes, fill with
water, and then the pipes contract as they cool. At an
eighth inch per ten feet, that's a lot of water that needs
some place to go. With no air traps it's going to try to
expand the pipes, and that of course can lead to ... whoosh!
Another nephew also learned the hard way to use them.
The pipes wil,l hammer like crazy anytime anyone turns off a
faucet with anything more than a gentle motion. I had him
put a 50' water hose on his outside faucet and it actually
almost stopped the hammering. After that he believed.
Without a stand pipe however, you can hear his toilet
gurgling all the way out into his driveway! Would you
believe he's, uhhh, cheap? G He puts up with the toilet
noisebut did add some air "traps".

Pop



Are they required by code anywhere? If not, I'd bet
they're mostly
installed at every faucet in architect designed homes for
"cost no
option" buyers with rigid monitoring of the as built
finished work.

About 30 years ago I was getting "shocks" when the
solenoid valves in
our clothes washer slammed shut. I installed a couple of
"shock
absorbers" which had spring loaded pistons in them, with
the backside of
the pistons open to atmosphere. They were sold for that
purpose and
advertised as being resistant to becoming water logged,
and could be
mounted at any angle.

Those worked as advertised, but I always wondered how long
it would take
before the piston seals would give out and water would
start leaking out
their back ends. In my case they were out in the open, so
I could spot a
leak if one occurred, but I'm not sure I'd have the guts
to seal them up
in a wall.
--

Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can smile when things are going wrong, you've
thought of someone
to blame it on."