PDC Spas OEM FLT-171-CART spa filter (C-4405)

LifeStyle, XD2 spa side, and River

Replacement numbers

Unicel C-4405, Pleatco PRB25SF-JH-PAIR

Fits PDC Spas OEM FLT-171-CART.

Diameter 4-15/16" (125 mm)Length 6-5/8" (168 mm)25 sq ft1 model listed

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UnicelC-4405
PleatcoPRB25SF-JH-PAIR (Spec table PDF p.32: PRB25SF, 5" × 6-5/8", 2-1/8" open, 3 oz, 25 sq ft, case quantity 12. PRB25SF-PAIR and PRB25SF-JH-PAIR, same body, 50 sq ft, case quantity 6. Cross-reference PDF p.47: C-4405 = PRB25SF-JH-PAIR.)
FilburFC-2387
Top2-1/8" (54 mm) / open
Bottom2-1/8" (54 mm) / open
Ø 4-15/16" (125 mm)6-5/8" (168 mm)Side view · end views belowTopBottom
Top: 2-1/8" (54 mm) / open
Bottom: 2-1/8" (54 mm) / open
Drawn to scale from the listed diameter and length and open-end sizes. Handles, threads and closed ends are drawn as symbols, not to scale. 25 sq ft media.

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For PDC Spas, C-4405 cartridge (OEM FLT-171-CART) sits in LifeStyle, XD2 spa side, and River. The cross-reference prints OEM FLT-171-CART; Unicel C-4405; Pleatco PRB25SF-JH-PAIR; Filbur FC-2387. 4-15/16" across, 6-5/8" long, top 2-1/8" / open, bottom 2-1/8" / open, 25 sq ft.

Catalog note for FLT-171-CART: Shown at 25 sq ft because that is what PDC’s 2025 guide prints for the element (LifeStyle, XD2 spa side, and River, 2010 to present), 5" × 6-5/8", 2-1/8" holes, named as Unicel C-4405. Unicel’s OEM cross-reference prints 50 in the square-foot column for C-4405, and the spec note says two cartridges per set. The spec row itself does not print a square-foot figure. Pleatco prints PRB25SF at 25 sq ft for one cartridge and PRB25SF-JH-PAIR at 50 sq ft, and its cross sends C-4405 to the pair. Filbur prints FC-2387 at 50 sq ft, “6 sets,” with the same two-per-set note.

C-4405 (OEM FLT-171-CART), Pleatco side: Spec table PDF p.32: PRB25SF, 5" × 6-5/8", 2-1/8" open, 3 oz, 25 sq ft, case quantity 12. PRB25SF-PAIR and PRB25SF-JH-PAIR, same body, 50 sq ft, case quantity 6. Cross-reference PDF p.47: C-4405 = PRB25SF-JH-PAIR..

FLT-171-CART, Filbur note: Dimensional listing PDF p.9 (printed p.16): FC-2387, 4-15/16" × 6-5/8", 2-1/8" open, PRB25SF-PAIR/JH, C-4405, 50 sq ft, 6 sets. Note: two cartridges per set with stick handle. PDC Spas section does not list FC-2387..

Hot tubs named for FLT-171-CART: LifeStyle, XD2 spa side, and River, years 2010 to present, listed by PDC Spas Common Replacement Filter Elements (2025) (FLT-171-CART. The XD2 cold side from 2024 is FLT-1000-CART, not this cartridge.).

Hold C-4405 next to PRB7B differs by no Unicel number, Pleatco PRB7B, no Filbur number, 5" diameter, 4-5/8" long, 17 sq ft, OEM FLT-118, note says PDC’s 2025 guide is the only size: Timeless and XTR, 2000–2005, FLT-118, Pleatco PRB7B, 17 sq ft, 5" × 4-5/8", 2-1/8" holes. Pleatco’s 2023 deactivated list prints PRB7B with replacement N/A, and the spec table has no PRB7B row. Unicel’s PDC block lists C-4401 at 35 sq ft, 4-15/16" × 4-5/8", two per set, and does not print FLT-118 or PRB7B. Filbur’s PDC section prints that C-4401 set (FC-2386) and does not print PRB7B. Pleatco does not say PRB7B was replaced by PRB17.5SF-PAIR.; 4CH-15 differs by Unicel 4CH-15, no Pleatco number, no Filbur number, 4-5/8" diameter, 5-3/16" long, top dual bar handle, bottom 1-1/2" SAE, 15 sq ft, OEM FLT-1000-CART, note says PDC’s 2025 guide: XD1, XD1+ and the XD2 cold side, 2024 to present, FLT-1000-CART, 15 sq ft, 4-5/8" × 5-1/4", 1-1/2" SAE on the bottom, bar handle on a closed top, Waterway 817-0020. Unicel’s Waterway line prints 817-0020 as 4CH-15 at 4-5/8" × 5-3/16", dual bar handle, 1-1/2" SAE, 199 pleats, 3 oz, 15 sq ft. The length differs by 1/16". The dimensions on this row are Unicel’s. Pleatco’s 2023 cross-reference has no 4CH-15 and no 817-0020. Filbur’s PDC section does not list it. The XD2 spa side is FLT-171-CART, not this cartridge..

Left blank on purpose: Area 25 sq ft (PDC; Pleatco single PRB25SF) vs 50 sq ft (Unicel OEM column; Filbur FC-2387; Pleatco pair). Diameter 5" (PDC, Pleatco) vs 4-15/16" (Unicel, Filbur). Filbur’s PDC section does not list this cartridge. Unicel’s PDC block does not list C-4405..

Source locations for this PDC Spas row: PDC Spas (manufacturer filter guide, 2025) on C-4405 (LifeStyle, XD2 spa side, and River, 2010–present: FLT-171-CART, 25 sq ft, 5" × 6-5/8", 2-1/8" holes, Unicel C-4405). Unicel 2026 Replacement Guide on C-4405 (Spec table PDF p.8 (printed p.4): C-4405, 4-15/16" × 6-5/8", 158 pleats, 4 oz, two per set. OEM cross-reference prints 50 sq ft. PDC block does not list C-4405.). Pleatco 2023 Catalog on C-4405 (PDF p.32: PRB25SF at 25 sq ft and PRB25SF-JH-PAIR at 50 sq ft. PDF p.47: C-4405 = PRB25SF-JH-PAIR.). Filbur Catalog & Reference Guide on C-4405 (PDF p.9 (printed p.16): FC-2387 = C-4405, 50 sq ft, 6 sets, two per set.).

Hot tubs listed for this cartridge

The rest of the PDC Spas model list is the PDC Spas filter by model and year lookup.

Model / systemYearsListed by
LifeStyle, XD2 spa side, and River (FLT-171-CART. The XD2 cold side from 2024 is FLT-1000-CART, not this cartridge.)2010 to presentPDC Spas Common Replacement Filter Elements (2025)

Check the cartridge you removed

Measure diameter, length, and both ends, then compare them with the figures above. The steps are in the measuring guide. Why the bottom decides whether it seals: open-end vs threaded filters. Power, the retainer, and not running the spa empty: how to install a cartridge. Number formats: how Filbur, Unicel and Pleatco numbers compare.

The same C-4405 number is also on the Beachcomber page.

Other PDC Spas cartridges

All 7 PDC Spas spa filters

Every number on this row, on one screen: cross-reference lookup. Published clean and replace intervals for this cartridge, and a buy link for the numbers above: replacement schedule and reorder. The interval comparison by brand: calculator.

Cleaner and test strips

Hose rinse and soak steps are in how to clean a cartridge. Named cleaners and strips are in filter cleaners and test strips.

Filter cleaner and test strips

Sources

Not in sources: Area 25 sq ft (PDC; Pleatco single PRB25SF) vs 50 sq ft (Unicel OEM column; Filbur FC-2387; Pleatco pair). Diameter 5" (PDC, Pleatco) vs 4-15/16" (Unicel, Filbur). Filbur’s PDC section does not list this cartridge. Unicel’s PDC block does not list C-4405..