Pool Filter Lab

Cartridge record

Unicel 4CH-21

Also sold asPleatco PTL18PPleatco PTL18P4Filbur FC-0121OnCore OC-408NOEM 20245-238OEM PVT 25N

cross-checked against 3 sources

Verified specifications

The selected value is shown first. Expand any row to compare the source values retained by the dataset.

Cartridge specifications
Outside diameter4-5/8"
Source values
  • unicel 4-5/8"
  • pleatco 4-7/8"
Length8"
Source values
  • unicel 8"
  • pleatco 8-3/16"
Top cap/ molded cone handle
Source values
  • unicel / molded cone handle
  • pleatco Handle
Bottom cap/ 1-1/2” male thread/MPT
Source values
  • unicel / 1-1/2” male thread/MPT
  • pleatco PAD AD
Pleats158
Source values
  • unicel 158
Filter area19 sq ft
Source values
  • unicel 19
  • pleatco 18
Media weight3 oz
Source values
  • unicel 3
  • pleatco 3

Equivalent part numbers

Match the complete printed string. Similar-looking part numbers can describe different end caps or lengths.

Cross-reference equivalents
BrandPart numberVerification
Unicel4CH-21cross-checked against 3 sources
PleatcoPTL18Psingle-source
PleatcoPTL18P4single-source
FilburFC-0121single-source
OnCoreOC-408Nsingle-source
OEM20245-238single-source
OEMPVT 25Nsingle-source

Known equipment fits

Fitments are source-attributed. Confirm the housing model and cartridge measurements before ordering.

Filter and spa fitments
BrandModelOEM partSource
Alcove SpasPageant Spa—pleatco single-source
Alcove——unicel single-source
Atera Spas (Four Seasons Home Resort Products)——unicel single-source
Atera SpasPageant Spa—pleatco single-source
Dream Maker Spas——unicel single-source
Pageant SpasPageant Spa—pleatco single-source
Pageant Spas——unicel single-source
Saratoga SpasPageant Spa—pleatco single-source
Saratoga Spas—20245-238unicel single-source
Unicel19 sq.ft. top load—unicel single-source
Vita SpaPageant Spa—pleatco single-source
Vita Spas—PVT 25Nunicel single-source

Browse related equipment

Source notes

Dimension neighbors

Records with the same outside diameter and a different length appear first, followed by the closest diameters. End-cap details still need to match.

4CH-925

4-5/8" × 7-1/4"

cross-checked against 2 sources

4CH-20

4-5/8" × 6-3/4"

cross-checked against 3 sources

4CH-920

4-5/8" × 6-3/4"

single-source

C-4303

4-5/8" × 6-3/4"

cross-checked against 2 sources

4CH-24

4-5/8" × 9-3/4"

cross-checked against 3 sources

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