The Hypro D252 Valve Kit 2408 includes the 4 Valves and 4 o-rings. If your pump is not drawing water or the flow is irregular then it could indicate the valves are not seating properly. If you are having trouble with your valves it could be that debris has gotten into them. To replace the valves is very simple, just remove the head by removing the bolts first, then remove the valve caps and valve assemblies. Hypro designs their diaphragm pumps to make regular pump maintenance simple and affordable, all normal wear parts are easily accessible.