
calculating psi  
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Posted by: sait2010 ^{®} 02/16/2010, 14:05:58 Author Profile eMail author Edit 
If a building is 40 feet high and the psi at the top is 15 psi how do I calculate the psi needed at the base? I know it is probably a variation on a formula I have. Adversly, if the psi at the base is given, how do I calculate the psi at the top? 
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: calculating psi  
: calculating psi  sait2010  Post Reply  Top of thread  Engineering Forum 
Posted by: Marky ^{®} 02/16/2010, 15:14:20 Author Profile eMail author Edit 
Hi and welcome to the forum.....Homework? 
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: : calculating psi  Marky  Post Reply  Top of thread  Engineering Forum 
Posted by: sait2010 ^{®} 02/16/2010, 15:40:44 Author Profile eMail author Edit 
not homeworkhusband is plumber and forgets how to calculate in this application. 
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: : : calculating psi  sait2010  Post Reply  Top of thread  Engineering Forum 
Posted by: Kelly Bramble ^{®} 02/16/2010, 17:19:00 Author Profile eMail author Edit 
Your wanting to calculate the pressure due to the weight of the water column. Assuming a cylindrical pipe.. volume in.^3 = 3.14157 x r(in.)^2 x height(in.) in. = inches
one cu inch water weights 0.036127 lbs Therefore; Pressure at bottom (psi) = [(Calculated volume lbs/in^3) x 0.0.036127 lbs] + 15 psi Somebody check my math... Modified by Kelly Bramble at Tue, Feb 16, 2010, 17:19:42 
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: : : : calculating psi  Kelly Bramble  Post Reply  Top of thread  Engineering Forum 
Posted by: zekeman ^{®} 02/16/2010, 20:20:21 Author Profile eMail author Edit 
First of all I doubt the plumber simply wants the water pressure of an open system. I would make a small bet that he wants to size a circulating pump for a building 40 feet high, and if so, should ask the basic question. The answer to the OP question:
Assuming I won the bet, a circulating pump in a closed system does not need to produce that value of pressure. Plumbers often make that mistake. It would behoove the plumber to state the problem he has for a proper answer. 
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