New centrifugal (impeller) solar pumps just arrived. There are two models which are 4" 500W and 4"1000W.
The centrifugal solar pumps preduce much more flow than screw solar pumps but less head.
4"500W centrifugal solar pump is suitable for total head between 20m-50m
4"1000W centrifugal solar pump is more suitable for head between 50m-90m.