Hot Spot OEM 31489 spa filter (C-6430)

Hot Spot (Hot Spring family)

Replacement numbers

Unicel C-6430, Pleatco PWK30-4

Fits Hot Spot OEM 31489, 71825, 71826.

Diameter 6" (152 mm)Length 10-1/2" (267 mm)30 sq ft9 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 Hot Spot, C-6430 cartridge (OEM 31489) sits in Hot Spot (Hot Spring family). 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 these OEM numbers under Hot Springs Spas and directs Hot Spot owners there; Hot Spot model fitment is from Leisure Time Inc.; Leisure Time Inc.: Use this pleated cartridge only where the spa specifies 71825 or its listed equivalent. Models requiring Tri-X cartridges must use the appropriate Tri-X filter.; 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).

Model list attached to C-6430 cartridge (OEM 31489): Hot Spot Pace, years 2020–2026, listed by Leisure Time Inc. dealer listing; Hot Spot RE Z, years 1998–2002, listed by Leisure Time Inc. dealer listing; Hot Spot RLX Z, years 1998–2002, listed by Leisure Time Inc. dealer listing; Hot Spot SE, years 1998–2000, listed by Leisure Time Inc. dealer listing; Hot Spot SLX, years 1998–2002, listed by Leisure Time Inc. dealer listing; Hot Spot SLXtra, years 2001–2002, listed by Leisure Time Inc. dealer listing; Hot Spot Stride, years 2019–2026, listed by Leisure Time Inc. dealer listing; Hot Spot SX, years 2011–2026, listed by Leisure Time Inc. dealer listing; Hot Spot TX, years 2011–2026, listed by Leisure Time Inc. dealer listing.

Before ordering C-6430, compare it with 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 Unicel lists these OEM numbers under Caldera Spas; the Hot Spot Sorrento fitment is from Leisure Time Inc.; Leisure Time Inc.: For a 2024 Makena, confirm the spa serial number before ordering. Other Makena years use a different cartridge.; and C-4326 differs by Unicel C-4326, Pleatco PRB25-IN, Filbur FC-2375, 4-15/16" diameter, 13-5/16" long, top 2-1/8" / open, bottom 2-1/8" / open, 25 sq ft, OEM 33521.

Where those figures are printed: Unicel 2026 Replacement Guide on C-6430 (OEM cross reference (Hot Springs Spas 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

Model / systemYearsListed by
Hot Spot Pace2020–2026Leisure Time Inc. dealer listing
Hot Spot RE Z1998–2002Leisure Time Inc. dealer listing
Hot Spot RLX Z1998–2002Leisure Time Inc. dealer listing
Hot Spot SE1998–2000Leisure Time Inc. dealer listing
Hot Spot SLX1998–2002Leisure Time Inc. dealer listing
Hot Spot SLXtra2001–2002Leisure Time Inc. dealer listing
Hot Spot Stride2019–2026Leisure Time Inc. dealer listing
Hot Spot SX2011–2026Leisure Time Inc. dealer listing
Hot Spot TX2011–2026Leisure Time Inc. dealer listing

Other Hot Spot models and years are in the Hot Spot section of the Hot Spring filter by model and year lookup.

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: Hot Spring filter sizes by collection. Number formats: how Filbur, Unicel and Pleatco numbers compare.

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

Other Hot Spot cartridges

All 5 Hot Spot 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