Caldera OEM 31489 spa filter (C-6430)

Caldera Vacanza (Watkins)

Replacement numbers

Unicel C-6430, Pleatco PWK30-4

Fits Caldera OEM 31489, 71825, 71826.

Diameter 6" (152 mm)Length 10-1/2" (267 mm)30 sq ft2 models listed

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UnicelC-6430
PleatcoPWK30-4
FilburFC-3915
Top1-15/16" (49 mm) / open
Bottom1-15/16" (49 mm) / open
Ø 6" (152 mm)10-1/2" (267 mm)Side view · end views belowTopBottom
Top: 1-15/16" (49 mm) / open
Bottom: 1-15/16" (49 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. 30 sq ft media.

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For Caldera, C-6430 cartridge (OEM 31489) sits in Caldera Vacanza (Watkins). The cross-reference prints OEM 31489, 71825, 71826; Unicel C-6430; Pleatco PWK30-4; Filbur FC-3915. 6" across, 10-1/2" long, top 1-15/16" / open, bottom 1-15/16" / open, 30 sq ft.

31489 carries this note from the catalogs: Unicel lists OEM 31489 under Hot Springs Spas; the Caldera Vacanza fitment for 31489 is from Leisure Time Inc.; Leisure Time Inc.: Replaces compatible 71825 or 31489 pleated cartridges. Models requiring Tri-X cartridges must use the appropriate Tri-X filter. Unicel's 2026 price list (not its spec table, which still prints C-6430 with 4 oz media) says "C-6430 USE C-6430AM", the antimicrobial version (30 sq ft, Watkins replacement).

Hot tubs named for 31489: Vacanza Celio, years 2019–2026, listed by Leisure Time Inc. dealer listing; Vacanza Tarino, years 2013–2026, listed by Leisure Time Inc. dealer listing.

C-6430 is easy to confuse on the Caldera table. C-7350 differs by Unicel C-7350, Pleatco PCD50N, Filbur FC-3963, 7" diameter, 10-3/4" long, top semi-circular handle, bottom 2-11/16" / open, 50 sq ft, OEM 1019401, note says Leisure Time Inc.: For a 2024 Makena, confirm the spa serial number before ordering. Other Makena years use a different cartridge.. C-7451 differs by Unicel C-7451, Pleatco PCD50, Filbur FC-3084, 7" diameter, 10-3/4" long, top semi-circular handle, bottom 2” male slip fitting, 50 sq ft, OEM 033016, note says Unicel: C-7350 can also be used.

Where those figures are printed: Unicel 2026 Replacement Guide on C-6430 (OEM cross reference (Caldera section), PDF p.39 (printed p.35); spec table PDF p.12 (printed p.8)). Pleatco 2023 Catalog on C-6430 (Unicel-to-Pleatco cross reference, PDF p.47). Filbur Catalog & Reference Guide on C-6430 (Product by Pool/Spa Manufacturer (OEM), Hot Springs, printed p.38 (PDF p.20)). Leisure Time Inc. (Hot Spring/Caldera dealer) on C-6430 (Compatibility section: model and model-year list). Leisure Time Inc. (Hot Spring/Caldera dealer) on C-6430 (Compatibility section: model and model-year list).

Hot tubs listed for this cartridge

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

Model / systemYearsListed by
Vacanza Celio2019–2026Leisure Time Inc. dealer listing
Vacanza Tarino2013–2026Leisure Time Inc. dealer listing

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. Brand notes: Caldera filter bottoms. Number formats: how Filbur, Unicel and Pleatco numbers compare.

The same C-6430 number is also on the Hot Spring, Hot Spot, Solana pages.

Other Caldera cartridges

All 10 Caldera 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