Dosing Pump Non Return Valves Non return valves for use with metering and dosing pump installations. These spring loaded ball check valves can be fitted in the hose line and prevent mixing and back flow. Manufactured from Polyvinylidene Fluoride (PVDF) with PTFE seals they are compatible with Prominent’s range of metering and dosing pumps and accessories. Available to fit 6mm x 4mm, 8mm x 5mm and 12m x 9mm tubing.