Keystone, you are correct in the back pressure comment for a rotary vane pump , ie Gast 0523 10 psi max comparison,This is why we use dual piston custom built Wobl pumps of 4.4 CFM @ 20 psi as these will keep the line clear of condensation in PineGroves situation.Single line to pondside and split from there with a pair of 500-700 gpm diffusers (3 ft of depth) Back pressure will be 10-15 psi max and pump can take 30psi.I see you are a Koender dealer dont you have a water pump as mentioned??
