Most Waterway hot tub pump parts are interchangeable between the Executive 56 frame and Executive 48 frame pumps, but volutes #9 are not interchangeable due to through bolt spacing. Waterway hot tub pumps built before 2010 may have different faceplates #4, the current style faceplate will not fit the older Waterway volutes (#9) For older pre 2010 Waterway pumps it's best to replace the complete wet end.