Length of all pipe plus number and type of fittings on the return to the pond would be needed to be calculated. This resistance will determine drop needed to supply enough pressure. A rough estimate of 12' pipe plus a few fittings would be 5 inches drop needed for a 3" pipe and 27" inches drop needed for a 2" pipe. This was just a quick estimate to show 2 vs 3 pipe. Don't use 2" pipe.
Last edited by batman; 05-19-2019 at 01:43 PM.
The real Batman wears polyester! Don't be fooled by the plastic imposter.