This diaphragm is the flexible pumping element inside the sprayer’s pump head. It separates the hydraulic drive chamber from the fluid being pumped, converting reciprocating motion into pressure for the spray circuit. A ruptured or fatigued diaphragm causes a loss of pump pressure and uneven spray output, often seen as a pulsing flow at the nozzles. The manufacturer machines the diaphragm to match the original pump head’s clamping geometry, ensuring a proper seal without additional gaskets. On installation, inspect the pump head surfaces for debris or corrosion that could compromise the seal.