water hammer/well pump surges
Posted by Bud... Suncoast Plumbing Inc. on October 29, 1998 at 19:35:40:
i have a farm well system consisting of a 5 hp pump, 120 psi output to the irrigation system through 4" pvc rubber jointed pipe at about 80 gallons per minute. I have a problem with the well pump cutting off and on causing water hammer in the system and possible pipe damage later on. Is there a way to redesign my system or add an accessory to handle this problem?

David:---A basic understanding of the dynamics of water in motion will help you in solving the pipe failure problems. Water weighs 8.33 lbs. per gallon....a 4" PVC water line can carry 500 gallons easily (depending on its' developed length. 500 X 8.33 = 4165 lbs. of water in that line. Now excellerate that mass of water to any given velocity through that pipe and shut off the pump abruptly or close a fast acting valve to quickly. You will have to then deal with the result of 2 tons of water that would rather continue the trip than stop. The laws of motion apply to liquids as well as solids. You may wish to consider the installation of several large captive air storage tanks at several strategic areas on your farm. These Tanks will act as shock absorbers to deal with the hydrodynamic forces at play, and will provide you with additional storage for the water. This will in turn reduce the short cycling of your pump and the resultant surges induced. Place one tank at the most remote end of the 4" run of pipe, and add one or two more until the desired effect is realized...Lots of luck Bud....A good source for captive air



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