A.Y. McDonald 21050K Bronze Well Pump End Only 10 GPM 0.5 HPA. Y. McDonald offers a full line of four inch submersibles ranging from 1 3 to 5 horsepower, with flow rates ranging from 5 to 25 GPM. Our 21000 submersibles offer peak capacity performance in 5, 7, 10, 15, 20 and 25 GPM models. All K Series No Lead Pumps come with a 1 1 4" discharge and sizes range from 1 3 to 5 horsepower (HP). Two wire models up to 1 1 2 horsepower (HP) or three wire models up to 5 horsepower (HP). A. Y. McDonald 2100 Series