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 calculating psi Post Reply Engineering Forum
 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?

 : : calculating psi : : 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 homework-husband is plumber and forgets how to calculate in this application.

 : : : calculating psi : : : 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 r = radiusone cu inch water weights 0.036127 lbsTherefore;Pressure at bottom (psi) = [(Calculated volume lbs/in^3) x 0.0.036127 lbs] + 15 psiSomebody check my math... Modified by Kelly Bramble at Tue, Feb 16, 2010, 17:19:42

 : : : : calculating psi : : : : 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: pressure of a 40 foot column of water is 40/34*14.7=17.3 psi since it is well known that 34 feet of water is one atmosphere.And the pressure at the bottom is 17.3+14.7=32.0 psi. Another way to do the column is to take a column of water 1 square inch and 40*12 inches high Its weight would be the pressure due to the column. Taking the density of water. 0.0361 this comes to 40*12*.0361=17.33 psi, the same as before. What is the application ?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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