### water pressure calculations

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Can anyone give me the formula to calculate water pressure given these knowns. Tank size = 200 gallons Head = 25 feet Delivery pipe diameter = 3/4 inch Distance of travel = 60 feet

Thanks

-- Doug Shutes (toadshutes@yahoo.com), February 17, 2000

Doug,

http://www-sci.lib.uci.edu/HSG/RefCalculators4.html#CIV-HYDRO

Also plunder about the page - I've never seen so many different kinds of calculators in my life.

j

-- j (jw_hsv@yahoo.com), February 17, 2000.

I've not checked the sources that j gave, but might be able to help a little. Tank size does not affect water pressure, only the height of the water in it. Water pressure at the bottom of a column of water is height of the column in feet X 0.434, which means that your head will yield 10.85 psi. Friction loss in pipe depends upon the kind of pipe, i.e. copper, steel, or plastic, and also depends on the gallon per minute flow within the pipe. Huh? That's what my "Pocket Reference" says. Perhaps the other charts will help.

-- greenbeanman (greenbeanman@ourtownusa.net), February 17, 2000.

Keep it simple, its all in the height of your water tank. This is from the book The Home Water Supply. "As always, 2.3 feet of elevation will produce one pound of pressure". Your pipe run is not enought to worry about. Gary

-- Gary Hart (bathtubspring@hotmail.com), February 17, 2000.

Gary has it rigth, Doug--2.31 feet elevation per psi. But this is the total elevation. In other words, from the point where you measure the pressure to the highest point the water is at.

The size of the tank and the diameter of the pipe are immaterial insofar as "static" pressure. Your pressure when you are using water will decrease a bit, though. This is called "dynamic" pressure, and the diameter of the pipe plays a critacal role in this, and should not be ignored. The bigger the pipe, and the shorter the pipe, the less head loss (it's caused by friction between the flowing water and the walls of the pipe) for any given flow.

A lot of folks have a hard time believing that the pressure ten feet down in a swimming pool, for instance, is the same as the pressure at the bottom of a vertical ten foot pipe, but it's true.

-- jumpoff joe (jumpoff@echoweb.net), February 18, 2000.

Sorry, Greenbeanman, you're right too; I somehow skipped over your letter. .434 is the inverse of 2.31, by the way, which is why both of you guys have it right on the money. (close enough to the inverse, anyway)

I at first was not sure if Doug was including the head of his pipe, but I guess he must have been, or else his 200 gallon tank must be very tall and skinny :)

-- jumpoff joe (jumpoff@echoweb.net), February 18, 2000.

So the pressure will depend on how high your water colum is. Not on how long your pipe is. 10 feet elevation would be 4.33 psi or 50 feet would be 21.65 psi. If you are looking for higher psi you will need to elevate your tank. If your are pumping the water then your psi will be arted for the pipe and the pump and controlled by a pressure tank and switch. Hope that helps.

-- Chris (wtp5@tcsn.net), December 22, 2000.