9400.040 is the old pump, it is obsolete. It was based on the same Sicce pump many manufacturers use. Sicce makes the motor and the skimmer maker provides a needlewheel and volute, etc. We could not get the pumps to be quiet enough and had problems with the shaft breaking so we developed our own pump.
9420.040 is our own needlewheel pump. It was built to be a needlewheel pump from the ground up. It is much quieter and uses a rare earth impeller magnet with a thicker ceramic shaft and ceramic bearings. It also has a built in cooling port. It uses less power than the older pump as a result. We greatly reduced the number of parts by molding the mixing chamber to the motor and we secure the impeller cover with a stainless steel screw so it cannot unintentionally loosen and result in a broken shaft, a problem we were having with the 9400.040.
9410.040 is just the smaller version for the 9410 skimmer. Smaller motor coil and needlewheel, that is the only difference.
