Sta-Rite 170145 System 3 S7M120 Large and Small Cartridge Set, 25021-0200S and 25022-0201S

Pentair 170145 is the genuine replacement cartridge pack for the Sta-Rite System 3 S7M120, the 21 in. modular media filter. It contains both elements the filter uses: the 25021-0200S inner cartridge and the 25022-0201S outer cartridge.

Two cartridges that work as one

The System 3 nests a smaller cartridge inside a larger one. The inner element measures 11 in. by 11 in. by 31.25 in. and the outer 19 in. by 19 in. by 23 in. Together they give the filter its full surface area, which is why replacing only one of them rarely brings performance back.

When to replace

Cartridges are cleaned many times over their life, but eventually hosing no longer returns the pressure gauge to its clean reading, and pleats start to fray or collapse. That is the point to fit a new pack rather than keep cleaning.

Before you order

This pack fits the S7M120 only. The S8M150, S7M400 and S8M500 in the same family take different cartridges. The model is on the tank label.