check valves

[Tickridgescott]

I am going to install a submersible pump in a spring catchment cistern about 200 to 220 feet below the holding cistern right outside the house. The overall run is 1300 feet but the elevation difference is about 200 to 220 feet.

I am running 1" 200 PSI Black PE water pipe. Gould's pump techs state that you should install a check valve every 200 feet of elevation rise. They could not tell me why though. LOL. Can anyone here tell me why this may be the case? Do I need to install a checkvalve somewhere in that 1300 foot run? I would be right 'on the edge' in terms of whether it is necessary or not.

Thanks,
Scott

 

[Raucina]

I am sure you will get some contrary ideas, but when you shut off the flow of water suddenly you get a pressure surge - water hammer- because water is essentially incompressible. Slam on the brakes and your head hits the windshield - thats water trying to stop, and it can mean incredible pressures inside your pipeline. Several check valves divide that hammer into lesser pressures and save your pipe line. Do not use a swing check valve - look for a top quality spring loaded ball type check valve. Surplus center has some in 1.25" stainless steel for 15.00$ - I have several in service for years - looks like a 50$ valve to me. Of course you have the burden of maintenance and a pit to find the unit after we pass to the nether world, so there is a price to pay for this choice... Water hammer also has a practical application and that is the ram pump, which I am surprised has not come up in this forum to my knowledge - take a look at info about "rams" and you will quickly see how water reacts when forced to stop moving quickly.