Terry wrote:
Where did you learn this? "of a square column of water 1 inch on
each
side"

You make it sound like the density of water is dependent upon the
volume of
it's container.


Andy replies:

If the bolus of water is 1 inch on a side, the bottom area
of the column is one square inch. Pounds per SQUARE INCH
is the measurement we are interested in, so I used this
as an illustration.

The WEIGHT of the water is dependent on the volume of
the container ---- density is not the issue we are interested
in. However, the DENSITY is what we are dealing with when
when we say that 33.9 feet of water in a column one inch
on a side, weighs 14.7 POUNDS...... Since the base of the
column is ONE SQUARE INCH, the pressure is 14.7 pounds per
square inch...

This is also known as ONE ATMOSPHERE, or, the pressure of
a column of AIR , one inch on a side, extending from the
earth to space, at standard temperature and pressure, exerts
a force of 14.7 pounds per SQUARE INCH ,or ,ONE ATMOSPHERE....

Thats how I remember the value for water without having
to look it up...

If you are diving in water , at 33.9 feet below the
surface, the water pressure on you is 2 ATMOSPHERES, or,
29.4 psi.... ( Easy to remember if you take a scuba class)

Go look in the CRC tables, and it will list all this stuff.
Also, a general science book from high school should give
a similar explanation....

Sorry if my explanation was not in the manner that allowed
you to understand it..... it worked for me, and that's how
I remember it......

Finally,1 gallon of water = 231 cubic inches = 8.34 pound avor

You can work this backward and get the same answer.......


By the way, here's a GREAT rule of thumb.

1 foot of water is 1/2 psi. Not strictly precision,
but real easy to remember and close enough for alt.home.repair.

Andy , BS, MS, PE etc.etc.etc





"Andy" wrote in message
oups.com...
Andy adds:

I have seen "10 inches" of water specified on a number of furnace
devices. I thought
I would just post what that means and what it means in psi.

10 inches of water means the weight of a square column of water 1
inch on each side which
is 10 inches high .


To determine the psi;
Remember 33.9 feet high (406.8 inches) and 1 sq inch on a side is
14.7 pounds

Therefore , 10 inches : (10/406.8) = (Xpsi/14.7) psi is
0.36 psi

11 inches : 0.40 psi

So, these pressures represent a very low, but still positive
pressure.

Obiously, these very low pressures would be a pain to measure with
a
gauge, but really
easy with a manometer , hence "inches of water"....
Andy