Pentair Diffuser, 2 HP Full Rated / 3 HP Up Rated, High Pressure, 355545Z

The Pentair 355545Z is the high pressure diffuser for Challenger pumps rated 2 HP full rated through 3 HP up rated, and for the AF-75 and AFP-75 Waterfall models. Pentair carries the part under both 355545 and 355545Z.

What the diffuser does

The diffuser sits directly in front of the impeller and shapes the water leaving it, converting velocity into pressure and holding the running clearance the impeller was designed around. When it wears, cracks or loses its sealing face, the pump keeps turning but delivers less pressure and less flow, and the loss is often blamed on the motor or a clogged line.

Getting the right one

Pentair splits these pumps into high pressure and high flow versions, and each takes its own diffuser. Confirm the series along with the horsepower rating on the pump label before ordering, because a diffuser from the wrong series will not perform correctly even where it appears to fit.

The pre-1992 note

Pentair calls out one exception worth knowing. On pumps 2F and 2-1/2 A built prior to 10-1-92, the diffuser and the impeller must be replaced together as a pair. If your pump falls into that group, order both parts in one go rather than making two trips into the wet end.