On Fri, 20 Jan 2006 09:22:53 -0500, Phil Munro
wrote:

116 psi!!! Where did you get WATER at that presure? I always thought
leaks were tested with air presure. Water is not compresible, and
changes in temperature will change the presure, I think. --Phil

Again, no experience, and I thought I would learn about this here.
Some people here seem to have written as if using water is the normal
procedure, but others hint that it's not, or say to use air.

I offer this for the OP's consideration.
Water is only compressible to a slight degree, and the major thing
they could be compressing is the slight amount of air that may be left
in the pipes when they are is filled with water. Because that volume
is small, tThat means that it would only take the loss of a little bit
of air or a little bit of water (giving more room for the air), to
multiply the available space significantly and make the pressure drop
significantly.

Also, the air can get absorbed intio the water. This happens much
faster at high pressures, and iiuc when the air is absorbed in the
water, it takes up no space (amazingly) and thus the pressure would
drop.

Look at the water prssure arrangements in 6-story buildings. (In nyc.
There may be a different height where this applies in other places.)
I think the same thing applies with houses that have wells and
compression tanks.

Four or 5 stories and less, city water pressure is enough, Seven or 9
stories or more, they put a water tank on the roof.

At 6 stories they pump the water into a tank that is about 1/3 air
after the air in the tank is compressed, and they use the air pressure
to pump the water to the sixth floor (and the other floors, but for
the sixth it's essential) After a while the air in the compression
tank has been absorbed into the water, the pressure drops, and a
separate air pump has to be used to add more air. Here the water is
being replaced with new water every time someone uses any water,
unlike the OP's sealed pipe, but there is still absorption to the
extent the original water will take it.

renux wrote:

We're testing a new copper line for leaks.

The line was purged of air, filled with water at 116 psi, and monitored
with a pressure gauge.

After first night, pressure dropped to 102 psi.

After second night, pressure dropped to 92 psi.

This leads me to believe that there's a leak, however, there are no
signs of humidity whatsoever.

Is it possible for a line that shows no humidity (i.e. a line that
presumably has no leaks) to keep loosing pressure?

Is there a logical explanation for this?

Thanks in advance.



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