Pentair FNS® Plus 48 Sq Ft D.E. Filter
The Pentair FNS® Plus 48 Sq Ft D.E. Filter is a vertical-grid diatomaceous earth filter engineered for superior filtration performance and extended time between cleanings. Curved grids maximize filtration area, while refined internal hydraulics minimize flow restriction — requiring minimal pumping power to achieve the needed flow rate. Built with fiberglass-reinforced polypropylene for superior strength and reliability.
D.E. filters provide the finest filtration of any filter type — capable of filtering particles down to 3–5 microns. The FNS Plus adds convenience features including the Service-Ease™ grid pack for simplified cleaning, top-to-bottom backwash, Tension Control™ clamp, and Continuous High Flow™ internal air relief. ANSI Standard 50 certified. Backed by a 2-year warranty.
Key Features
48 Sq Ft D.E. Filtration
Curved grid design maximizes filtration area — more area means better performance and longer periods between cleanings.
Finest Filtration Available
D.E. filtration removes particles down to 3–5 microns — the clearest water achievable with any filter type.
Service-Ease™ Grid Pack
Simplified grid removal and cleaning — faster, easier annual teardowns.
Top-to-Bottom Backwash
Efficient backwash cycle cleans grids thoroughly from top to bottom.
Continuous High Flow™ Internal Air Relief
Integrated automatic air relief maintains optimal flow plus a High Flow™ manual air relief valve.
Tension Control™ Clamp
Secure, easy-to-operate clamp band for filter tank access.
Low Pumping Power Required
Refined internal hydraulics minimize flow restriction — more filter performance per watt of pump energy.
100% Factory Tested
Every unit pressure-tested at the factory before shipment.
Fiberglass-Reinforced Polypropylene Tank
Corrosion-resistant construction for long residential service life.
ANSI Standard 50 Certified / 2-Year Warranty
Certified performance and backed by Pentair's 2-year residential warranty.
Who It's For
- Pool owners who want the finest filtration available and the clearest possible water
- Pools in areas with heavy debris loads, dust, or algae risk where DE's micron filtration excels
- Anyone upgrading from sand filtration who wants significantly clearer water
- Residential pools and spas requiring ANSI Standard 50 certified filtration
Specifications
Performance
| Filtration Area | 48 sq ft |
| Filter Type | Vertical-Grid D.E. |
| Filtration Micron Rating | ~3–5 microns |
Tank & Plumbing
| Tank Material | Fiberglass-Reinforced Polypropylene |
| Bulkhead Fittings | 7-1/2 in centerline |
| Clean-Out Port | 1-1/2 in bottom |
| Valve / Plumbing Color | Black |
Physical
| Product Weight | 76 lb |
| Shipping Dimensions | 22.5 × 22.5 × 45 in |
Approvals & Warranty
| Certifications | ANSI Standard 50 Certified |
| Warranty | 2 Years |
What's in the Box
- Pentair FNS Plus Filter Tank with Curved Grid Pack
- Tension Control Clamp
- Multiport or Backwash Valve (see model configuration)
- User Manual
Note: Diatomaceous earth (D.E. powder) is not included and must be purchased separately.
Warranty
The Pentair FNS Plus 48 sq ft D.E. Filter comes with a 2-year manufacturer warranty. Clearflow Pool Supply is an authorized Pentair dealer and will assist with any warranty service needed.
Downloads
Frequently Asked Questions
How does D.E. filtration compare to sand and cartridge?
D.E. (diatomaceous earth) filters provide the finest filtration of the three common types — capable of filtering particles down to 3–5 microns vs. 20–40 microns for sand and 10–15 microns for cartridge. This produces noticeably clearer water. D.E. filters require periodic backwashing to clean the grids and annual teardown to thoroughly clean and re-charge with fresh D.E. powder.
What is diatomaceous earth and how much do I need?
Diatomaceous earth is a naturally occurring silica powder made from fossilized microscopic organisms. It coats the filter grids and provides the actual filtration medium. For the 48 sq ft FNS Plus, the typical D.E. charge is approximately 7.2 lbs of D.E. powder after backwashing or reassembly. Always follow the specific charge amount in the owner's manual.
What is the Service-Ease grid pack?
The Service-Ease grid pack is Pentair's design for simplified grid removal and reinstallation during annual cleaning. The grids are assembled as a single unit that lifts out together, rather than individually removing each grid — making annual teardowns faster and less cumbersome.