Cal Spas spa filter (C-4305)

Cal Spas

Replacement numbers

Unicel C-4305, Pleatco PMT50

Fits Cal Spas.

Diameter 4-15/16" (125 mm)Length 14-7/8" (378 mm)50 sq ft

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UnicelC-4305
PleatcoPMT50
FilburFC-1630
Top2-1/8" (54 mm) / open
Bottom2-1/8" (54 mm) / open
Ø 4-15/16" (125 mm)14-7/8" (378 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. 50 sq ft media.

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Cal Spas is the group name on the Cal Spas row C-4305 cartridge. Match these numbers: Unicel C-4305; Pleatco PMT50; Filbur FC-1630. 4-15/16" across, 14-7/8" long, top 2-1/8" / open, bottom 2-1/8" / open, 50 sq ft.

Before ordering C-4305, compare it with C-5374 differs by Unicel C-5374, Pleatco PLBS75, Filbur FC-2971, 5-5/16" diameter, 14-13/16" long, 75 sq ft, note says Filbur lists its FC-2971 equivalent at 5-5/16" x 14-11/16", 65 sq ft; and 5CH-752 differs by Unicel 5CH-752, Pleatco PCAL60-F2M, Filbur FC-0202, 5-3/16" diameter, 16-1/8" long, top bar handle, bottom 2” male thread/MPT, 75 sq ft, note says Leisure Time Inc. lists Cal Spas OEM 50753 for 5CH-752 (single retailer source, not shown as OEM). Filbur's catalog prints the Unicel number beside FC-0202 as "5CH-702".

Left blank on purpose: no model/model-year fitment in sources; Unicel lists no OEM part number for this brand entry.

Where those figures are printed: Unicel 2026 Replacement Guide on C-4305 (OEM cross reference (Cal Spas section), PDF p.30 (printed p.26); spec table PDF p.9 (printed p.5)). Pleatco 2023 Catalog on C-4305 (Unicel-to-Pleatco cross reference, PDF p.47). Filbur Catalog & Reference Guide on C-4305 (Product by Pool/Spa Manufacturer (OEM), Cal Spas, printed p.29 (PDF p.15)).

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-4305 number is also on the Sundance page.

Other Cal Spas cartridges

All 9 Cal 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: no model/model-year fitment in sources; Unicel lists no OEM part number for this brand entry.