Working with pvc

[JimE]

There is a point when friction loss is at its peak performance in pvc pipe sizing, after that you are adding extra water volume that is heavy and will cause additional head loss as the weight of the water is pushing down on your vertical pipe runs.

Uh, still no. I'll give you a visual. Three cylindrical tanks 23ft tall with identical pumps screwed directly into the bottom. 1st tank is 2"diameter (pipe), 2nd is 12"dia, 3rd is 10'diameter. Say for example, the pumps have a max head of 15' - all tanks would fill to the 15' level right? Ok, now you stick on 3 pumps with a max head of 40' - all tanks will completely fill and overflow at the exact same gpm (ignoring the friction loss in the 2"pipe). How can that be when the weight of 500,000 lbs of water in the 10' tank is pushing down on the pump? They all are pumping against 23' of head. If you stuck a pressure guage on the bottom of each tank there would be 10psi on all three. The situations are identical and the "weight" of the water has absolutely no bearing on the performance. And remember that pressure (or weight as you call it) is omnidirectional - it is distributed in all directions, not all of it directly down into the pump. Now does it make sense?

Jim


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