The height of the discharge fitting has changed. The “old style” Hi Flo pump was 7 1/2″ from bottom of faceplate to the top of the discharge fitting. The “new style” Hi Flo II is 8 3/16th ” to the discharge fitting. On a sand filter this should not have any impact. On some cartridge filters it may prove a problem. If there is a hard union in between the tank and the pump the height of the pump can cause you to “re plumb”. Although the threads on the intake and discharge are the same, their placement may cause you to use a “different ” connector to your filter, or you may have to move the pump a slight distance farther from the filter tank. We can help you with the fittings needed to convert @ http://www.waterwayparts.com