Waterway Plastics OEM 817-4035 spa filter (4CH-935)

Teleweir

Replacement numbers

Unicel 4CH-935, Pleatco PWW35L

Fits Waterway Plastics OEM 817-4035.

Diameter 4-15/16" (125 mm)Length 9-1/4" (235 mm)35 sq ft

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Unicel4CH-935
PleatcoPWW35L (Spec table PDF p.32: PWW35L, 5" x 8-1/2", 1-1/2" female SAE, 35 sq ft, OEM 817-4035. Cross-reference PDF p.47: 4CH-935 = PWW35L.)
FilburFC-0170
Topv-groove handle
Bottom2" female SAE
Ø 4-15/16" (125 mm)9-1/4" (235 mm)Side view · end views belowTopBottom
Top: v-groove handle
Bottom: 2" female SAE
Drawn to scale from the listed diameter and length. Handles, threads and closed ends are drawn as symbols, not to scale. 35 sq ft media.

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Teleweir is the group name on the Waterway Plastics row 4CH-935 cartridge (OEM 817-4035). Match these numbers: OEM 817-4035; Unicel 4CH-935; Pleatco PWW35L; Filbur FC-0170. 4-15/16" across, 9-1/4" long, top v-groove handle, bottom 2" female SAE, 35 sq ft.

Catalog note for 817-4035: Short Teleweir. Unicel and Waterway's table: 4-15/16" x 9-1/4", 35 sq ft, 2" female SAE, 219 pleats, for a 1-1/2" male SAE standpipe. Pleatco PWW35L is 5" x 8-1/2", 35 sq ft, OEM 817-4035, 1-1/2" female SAE. Filbur's Waterway row FC-0170 prints 817-4035 at 4-15/16" x 9-1/4" and 30 sq ft, with Unicel N/A. Nordic's chart uses this Waterway number as CARTRIDGE-T35. The 35 stored here is Unicel's and Waterway's figure.

4CH-935 (OEM 817-4035), Pleatco side: Spec table PDF p.32: PWW35L, 5" x 8-1/2", 1-1/2" female SAE, 35 sq ft, OEM 817-4035. Cross-reference PDF p.47: 4CH-935 = PWW35L..

817-4035, Filbur note: Waterway section PDF p.28: FC-0170, 4-15/16" x 9-1/4", 1-1/2" female SAE, OEM 817-4035, Unicel N/A, 30 sq ft..

4CH-935 is easy to confuse on the Waterway Plastics table. C-4326 differs by Unicel C-4326, Pleatco PRB25-IN, Filbur FC-2375, 13-5/16" long, top 2-1/8" open, bottom 2-1/8" open, 25 sq ft, OEM 817-2500, note says 25 sq ft open top-load. Unicel: 4-15/16" x 13-5/16", open 2-1/8", 106 pleats, 25 sq ft. Pleatco PRB25-IN lists OEM 817-2500 at 5" outside diameter and the same length. Filbur prints this OEM on two rows: FC-2375 at 13-5/16" (PRB25-IN, C-4326) and FC-2910, which the size table lengths at 13-1/4" and the Waterway section lengths at 12-1/4", with no Pleatco number. The size stored here is Unicel's. The 50 sq ft cartridge of the same length is 817-5000.. C-4950 differs by Unicel C-4950, Pleatco PRB50-IN, Filbur FC-2390, 13-5/16" long, top 2-1/8" open, bottom 2-1/8" open, 50 sq ft, OEM 817-5000, note says 50 sq ft open top-load. Same outside size as 817-2500. Unicel's spec note calls C-4950 an upgrade of the 25 sq ft C-4326: 212 pleats against 106, same 4-15/16" x 13-5/16" body. Pleatco PRB50-IN lists OEM 817-5000 at 5" outside diameter. Filbur FC-2390 agrees with Unicel's size and 50 sq ft. Waterway's table calls 817-5000 a 50 sq ft in-line top-load cartridge..

Left blank on purpose: Length 9-1/4" (Unicel, Waterway, Filbur) vs 8-1/2" (Pleatco). Area 35 vs Filbur's 30. Filbur prints no Unicel number on the 817-4035 row. Thread 2" female SAE (Unicel) vs 1-1/2" female SAE (Pleatco)..

Pages checked for 817-4035: Unicel 2026 Replacement Guide on 4CH-935 (Waterway list PDF p.64: 817-4035 = 4CH-935, 4-15/16" x 9-1/4", 35 sq ft. Spec table PDF p.8: 219 pleats, 2" female SAE, standpipe note.). Waterway Plastics Service Logic cartridge table on 4CH-935 (Fetched 2026-11-09: 817-4035, 35 sq ft, 4-15/16" x 9-1/4", SAE thread). Pleatco 2023 Catalog on 4CH-935 (Spec table PDF p.32: PWW35L, OEM 817-4035, 5" x 8-1/2", 35 sq ft. Cross-reference PDF p.47: 4CH-935 = PWW35L.). Filbur Catalog & Reference Guide on 4CH-935 (Waterway section PDF p.28: FC-0170, OEM 817-4035, 30 sq ft, Unicel N/A).

If you know the Waterway Plastics model and not the part number, use the Waterway Plastics 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. Number formats: how Filbur, Unicel and Pleatco numbers compare.

The same 4CH-935 number is also on the Nordic Hot Tubs page.

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Sources

Not in sources: Length 9-1/4" (Unicel, Waterway, Filbur) vs 8-1/2" (Pleatco). Area 35 vs Filbur's 30. Filbur prints no Unicel number on the 817-4035 row. Thread 2" female SAE (Unicel) vs 1-1/2" female SAE (Pleatco)..