The Check Valves in the pumps are held in place with an Internal Snap Ring. To replace a Check Valve, you must first remove the Internal Snap Ring. To do so requires a special tool called Snap Ring Pliers. These pliers have two tips that fit into the two holes of the Internal Snap Ring. By pressing the handles together, the two tips close the Internal Snap Ring allowing you to remove it from its installation location, a Snap Ring Groove.
Bison Pumps offers this specialized tool with properly sized tips to match the Internal Snap Rings that are installed in the Bison Pumps.