an improved diaphragm type chemical dosing pumps can be designed as both a variable displacement accurate dosing pump and a fixed displacement accurate dosing pump . the improved dosing pump provides a required supply of pressurized fluid , to be called hereafter as process fluid , to an injection point against varying gas or liquid pressures . by eliminating the use of elastomeric sealing , the failing of the pump due to seal wear is eliminated . an internal pressure relief valve protects the pump mechanicals from premature failure . use of a spring assisted suction assists positive suction for very accurate dosing . the working fluid is a driver fluid that is used to lubricate working components of the pump . the angled ports minimize friction losses to further improve pump efficiency and also eliminate building up of air pockets .