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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
: : 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.

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: : : 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 = radius 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
: : : : 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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