On 2/1/2012 5:57 PM, hr(bob) wrote:
On Feb 1, 5:45 pm, wrote:
We live at the peak of a small mountain.

We replaced our well water with city water
about 9 years ago.

City water was overall fine for first few years, low
pressure at first, due to our altitude, but the city upped
the pressure after the first year or so (to everyone in
this area) and tho not 'great' pressure after that, it
was adequate for a few years.

About 3 years ago I replaced our (30g, I think) hot
water heater with a larger GE 50 gallon tank.
(this may or may not be related)

There has been a few periods of hammer lock (pipes
beating/banging). Tho not certain, it seems these
may have happened before the water heater replacement.
Hammer lock has not come into play for the last year at
least.

We have water on ground level and a basement with a
washing machine. The water heater sits almost next to
washer, the master bath/shower is directly above the
water heater/washer. It's been suggested this may be
an issue.

That's all the details offhand -- the problem-

If water is running and someone opens a second
source, the pressure just quits. If one of the toilets
is refilling and the second one is flushed, they both
stop filling... usually hearing what I'd call a vapor lock.
This is the worst when dealing with anything in the
master bathroom (remembering water heater is directly
below). I can usually run the kitchen sink and also
open the sink in the hall bathroom. I can be running
the hose outside and turn on the kitchen sink or hall
bathroom. What I cannot do -- is be running anything
in the master bathroom and turn on something else.
This almost always results in the 'vapor lock' sound
and all pressure (but a VERY slight trickle) being lost.
Even turning on the shower in the m.bedroom is a
procedure. Having no other water running, the pressure
seems VERY strong in the tub, but often locks and quits
after a few second. To turn on the shower requires
pulling up the shower lever first, and slowly pulling
out the Moen (recently replaced) water valve. It's
been 'said' that the larger heater being directly below the
bathroom may be the cause. I've tried suggestions
for vapor lock, opening all valves, etc. I've recently
added a one-way valve in case pressure was being
pulled back down due to our altitude. A contractor
friend has no more suggestions, a longtime buddy
that was a plumber for quite a few years has no answers.
Anyone?

can you run multiple cold water devices other than the toilets? If
not, then you just have a pressure or flow problem, not an air lock.
If one device works ok, then pressure is not a problem, you have a
partial blockeage in the feed line. Do you have any neighbors at the
same altitude. I don;t see howw an airlock could posssssibly be to
blame.
Sounds to me like someone used teflon tape on a pipe joint and
accidentally wrapped tape over the end of the pipe. Sure seems to be a
blockage that is very persistent.

One other comment relating to pressure. If you are in the USA and the
city or water district is also supplying hydrants in the street for fire
fighting, then you must have enough pressure in the area to supply a
large volume of water to the hydrants. Your water will be supplied by
the same water line. Have you ever seen the fire dept. opening the
hydrants? They will do this annually to check them.

Paul