On Wed, 26 Apr 2006 23:41:38 GMT, Doug White wrote:

The reason for the fancy commercial ones is two-fold: 1) they will fit in
places where several feet of pipe might be a problem, and 2) the air in
the home brew version will slowly dissolve in the water, and the thing
will stop working. You can always shut off the water & drain the whole
system to get air back in, but why bother?

Maybe it's just my well pump, but I get plenty of air in the water
supply as it is. I have a clear hose that I attach to a faucet for
filling the fishtanks (beats lugging water around in 5-gallon pails),
and I get a _lot_ of bubbles in it, despite having a good connection to
the spigot. Maybe the iron filter process dissolves air into the water,
or something, but replenishment of air is definately not a problem in my
situation.

There are two kinds of water hammer. One is the loud bang you get when a
pressure pulse is created by a rapidly opening or closing valve (closing
is more common). The other is an oscillation in water pressure that can
make the pipes moan or in bad cases go bang bang bang as the water
pressure bops up & down. This requires flowing water.

Right. The gooseneck spigot I mention above does that if you turn both
sides on full blast at the same time, which is why I figure it's an
oscillation type thing.

Imagine blowing
over an open soda bottle, only under water. The big spikes can be
handled by pre-compressed piston jobs like the Oatey "Quiet Pipes" sold
at Home Despot & some hardware stores. However, eventually the pistons
can stick, and they won't work well for low pressure fluctuations. They
also make water hammer arrestors with a diaphram that are better for
stuff like that, and they can't stick. Those you'll need to get from a
plumbing supply place, probably special order.

I wonder if having a well and pressure tank takes some of that impulse
out of the system. Thinking as an electronics tech, it's a big
capacitor, but it's on the wrong end of a long inductor, so I'm not sure
that the high-frequency dampening will be significant. But yeah, if you
put another cap at the delivery end of the system, that makes the system
filter the impulses better. pi-filter, effectively. I think. That
class was a _long_ time ago.