Erie Tools 1 Hollow Shaft Triplex High-Pressure Washer Pump and Gearbox, 6.6 GPM, 5000 PSI Direct-drive triplex pressure washer pump. Maximum Pressure: 5,000 PSI Flow Rate: 6.6 GPM Requires: 1,560 RPM and 24 HP (18.5 KW) 1-inch hollow right-hand shaft.