Product Overview

Restore filtration performance in your Sta-Rite System:3 S7M400 Modular Media Filter with the Sta-Rite Mod Media Replacement Cartridge Set | 170146.

This genuine OEM replacement set includes both the inner and outer filter cartridges required for the S7M400 filter. Together, the two cartridges provide approximately 400 square feet of total filtration area, helping maintain strong water flow, efficient debris capture, and longer filtration cycles between cleanings.

The S7M400 uses a unique nested-cartridge design consisting of a smaller inner cartridge and a larger outer cartridge. Pentair / Sta-Rite part 170146 provides both elements together as a matched replacement set, making it an ideal solution when the original cartridges have become worn, permanently dirty, damaged, or difficult to clean.

Replacing both cartridges at the same time helps keep filtration balanced and avoids having to reopen the filter tank shortly after replacing only one element.

Key Features

• Genuine Pentair / Sta-Rite OEM replacement cartridge set

• Part number: 170146

• Designed specifically for the Sta-Rite System:3 S7M400

• Includes inner and outer filter cartridges

• Approximately 400 sq. ft. total filtration area

• Inner cartridge provides approximately 136 sq. ft.

• Outer cartridge provides approximately 264 sq. ft.

• Helps restore proper water flow and filtration performance

• Large filtration surface area supports longer intervals between cleanings

• Ideal replacement for worn, damaged, or heavily loaded filter media

• OEM fit for proper alignment inside the filter tank

• Suitable for residential in-ground pool filtration systems

Specifications

Pentair / Sta-Rite identifies 170146 as the complete inner and outer cartridge pack for the System:3 S7M400 400 sq. ft. filter.

Cartridge Dimensions

The S7M400 uses two different-sized modular filter elements.

Inner Cartridge

• Filtration Area: Approximately 136 sq. ft.

• Diameter: Approximately 18-1/2"

• Length: Approximately 16-1/4"

• Replacement Element: 25021-0223S

Outer Cartridge

• Filtration Area: Approximately 264 sq. ft.

• Diameter: Approximately 25-1/4"

• Length: Approximately 8-1/2"

• Replacement Element: 25022-0224S

Together, the two elements provide the approximately 400 sq. ft. filtration capacity required by the S7M400 system.

Compatible Filter

This replacement cartridge set is designed specifically for:

• Sta-Rite System:3 S7M400 Modular Media Filter

• 400 sq. ft. System:3 cartridge filter configuration

This is not a universal cartridge set. Always verify that your filter model is S7M400 before ordering.

When Should the Cartridges Be Replaced?

Cartridge filters can normally be cleaned and reused multiple times, but the media eventually wears out.

Consider replacing the cartridge set if:

• Filter pressure remains high after cleaning

• Water flow has noticeably decreased

• Cleaning intervals have become increasingly frequent

• Pool water is difficult to keep clear

• Pleats remain permanently discolored or clogged

• Filter media is torn or damaged

• Bands around the cartridge are broken

• End caps are cracked or deteriorated

• The cartridges have become permanently compressed

• Cleaning no longer restores normal system pressure

Replacing worn cartridges can help restore proper circulation while reducing unnecessary strain on the pool pump.

Why Replace Both Cartridges Together?

The S7M400 operates with an inner and outer cartridge working together as a complete filtration system.

Both elements:

• Process the same pool water

• Accumulate debris during the same operating hours

• Experience similar chemical exposure

• Affect overall system flow and pressure

For this reason, replacing both elements together helps maintain even filtration performance and eliminates the need to reopen the filter shortly afterward to replace the second cartridge.

Installation Information

Before servicing the filter:

1. Turn off the pool circulation pump.

2. Shut off any automatic equipment capable of restarting the pump.

3. Open the manual air-relief valve.

4. Confirm that all internal filter pressure has been released.

5. Open the filter tank according to Sta-Rite instructions.

6. Remove the existing outer and inner cartridges.

7. Clean debris from inside the filter tank.

8. Inspect internal components for damage.

9. Install the replacement inner cartridge.

10. Position the outer cartridge correctly around the inner element.

11. Reassemble the filter tank.

12. Secure the tank clamp according to the manufacturer's instructions.

13. Restart the circulation system.

14. Bleed trapped air from the filter.

15. Record the clean starting pressure for future maintenance reference.

Maintenance Recommendations

Cartridge cleaning frequency depends on factors such as:

• Pool usage

• Debris load

• Landscaping

• Water chemistry

• Circulation time

• Seasonal conditions

Monitor filter pressure rather than relying only on a fixed cleaning schedule.

When filter pressure rises noticeably above the clean starting pressure, inspect and clean the cartridges according to the equipment manufacturer's recommendations.

Maintaining balanced pool chemistry and proper circulation can also help extend cartridge life.

OEM Replacement Advantage

Using genuine Pentair / Sta-Rite replacement cartridges helps maintain the original hydraulic characteristics and fit of the System:3 filter.

The correct cartridge dimensions are important for:

• Proper seating inside the tank

• Correct water distribution

• Effective filtration

• Consistent system pressure

• Proper interaction between the inner and outer elements

Part 170146 provides the complete factory replacement set in a single package.

Frequently Asked Questions

What is Pentair / Sta-Rite part 170146?

Part 170146 is the genuine OEM replacement cartridge set for the Sta-Rite System:3 S7M400 Modular Media Filter.

How many cartridges are included?

The kit includes two cartridges:

• One inner cartridge

• One outer cartridge

What is the total filtration area?

The two cartridges provide approximately 400 square feet of total filtration area.

What are the individual cartridge sizes?

The inner element provides approximately 136 sq. ft., while the outer element provides approximately 264 sq. ft.

Does 170146 fit the S7M400?

Yes. 170146 is specifically designed for the Sta-Rite System:3 S7M400 filter.

What individual cartridges are included?

The set includes:

• 25021-0223S inner cartridge

• 25022-0224S outer cartridge

Can I replace only one cartridge?

The cartridges can be serviced individually, but if both have similar operating hours and wear, replacing the pair together can help maintain balanced filtration performance.

Is this an aftermarket cartridge set?

No. 170146 is a genuine Pentair / Sta-Rite OEM replacement set.

Important Safety Notice

Swimming pool filters operate under significant internal pressure.

Never loosen, open, or remove the filter tank clamp while the filtration system is pressurized.

Turn off the pump, open the manual air-relief valve, and verify that all internal pressure has been completely released before opening or servicing the filter tank.

Pool Supply Depot recommends professional service if you are unfamiliar with pressurized pool filter maintenance.