We are talking about water storage tanks.
One side says height of tank determines psi.
The other side says width and volume effects psi.
Would you please tell us how to find the psi of water
coming out the bottom of a tank?

1 ft. of head will give you 0.433 psi.
As long as the pipe from the tank is O.K. for the GPM that is being removed this will be the about the only thing that will effect the pressure. At static conditions it is the ONLY thing that will effect the pressure. At static conditions you can have a 1/2" pipe next to a 1 million gal. storage tank and at the same head you will have EXACTLY the same psi.

This is head pressure the tank is open and full. No additional pressure is added to it.

This goes for any diam. tank or pipe
PSI = H' x.434 or
PSI = H" x .036

PSI = Pounds per square inch

H' = Height in feet
.434 the PSI at the base of a 1" pipe 1' tall
.036 the PSI at the base of a 1" pipe 1” tall
the psi x the volume = total pressure is the pressure exerted on the entire base of the tank.
TP = H' x .434 x D²” x .7854

PRESSURE PER SQUARE INCH = (H’ x .434)

A 5 INCH STACK 75 FEET HIGH FILLED WITH WATER, WHAT IS THE PRESSURE PER SQUARE INCH AT THE BASE OF THE STACK?

ANS 32.55 psi

WHAT IS THE AREA OF THE 5 INCH PIPE? AREA = (D2” x .7854)

ANS. 19.64 sq. inches

WHAT IS THE TOTAL PRESSURE AT THE BASE OF THIS STACK?
T.P. = (H’x.434) (D²˝x .7854) ANS. 639 lbs.

SO the volume has nothing to do with the Pressure Per Square Inch WEW!

2.31 ' of H²O exerts a pressure of 1 psi at the base or psi = H' x 2.31 now that more like it.

Last edited by plumcass; 09-30-2008 at 06:45 PM.
Reason: Change H' x 2.31 to H' divided by 2.31