The Solinst Model 408 stainless steel double valve pump (DVP) is a pneumatic drive pump that allows consistent, high-quality samples. No bladder replacement is required, and the Double Valve Pump provides higher pumping rates than the Solinst Integra Bladder Pump. There is a selection of sizes and materials, variable flow rates, and it is field serviceable. The DVP is suitable for low-flow or regular-flow sampling. The stainless steel pumps can operate to depths of 500 ft (150 m), and the PVC Double-Valve Pump can operate to depths of 100 ft (30 m). Everything is easily accessible, replaceable, and interchangeable. All components can be cleaned with mild detergent or non-phosphate soap. Pumps are not damaged by operation in sediment-laden water or dry pumping conditions.Flow rates vary with the pump's depth below the surface, the depth below water level, the size of the drive and sample tubing, the drive and vent cycle times, the gas pressure applied, the aquifer recharge, and the size of the pump body.