Johnson Pump Baitwell Pump - 4.0 GPM - 12V. 5-chamber diaphragm pump features dramatically lower noise and water pulsation compared to 3- or 4-chamber designs. They are self-priming to 6.5' (8.2' for 5.2 gpm model), have an integrated pressure switch and can run dry without damage. Use an inlet strainer before pump intake. Connections for 3/8" NPT, 1/2" hose and 1/2" NPT, 3/4" hose.