The Delivery Valve for an RPD (Harben, also known as P Type) pump is a complete valve assembly including ball and o-ring. One delivery valve is required for each cylinder of the pump which can be 6-10 depending on the type of pump and whether the pump has pulsation.
The general symptom that occurs when delivery valves have failed is that high pressure water is going into the pump rather than out of it, and water is filling the crank case. In addition, oil might leak out of the holes in the top of the expansion chamber. It is recommended to change the inlet valves, delivery valves, and diaphragms all together while the pump is disassembled due to the intricate nature of the RPD pump.
