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Hot Tub Spa Filter Cartridges |
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How to measure your hot tub filter cartridge1. Measure the outside diameter of the cartridge (in inches, +/- 1/32"). 2. Measure the cartridge length (in inches, +/- 1/16") including end caps but excluding any handles or other extensions. Unicel recommends measuring through the center (if possible) rather than along the outside edge. 3. Identify the cartridge outside edge end cap configuration using the photograph chart. If the top and/or bottom is "open," measure the inside diameter (in inches, +/- 1/32") of the top and/or bottom. |
To look up the Unicel part number for your brand of spa, click to load the PDF file. Please be patient, this is a large file and may take a while to load. Once loaded, click on the alphabetical listing on the left side of the page for your spa brand.

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NEW! -
Micropure Micron
Disposable Filters Now available in many more common filter sizes! |
The chart below is ordered from the smallest diameter to largest and then by length, for those filters with the same diameter. You can also reference the Unicel part number on the right side of the chart.
If your hot tub filter is not listed, please contact us and we will be happy to help.
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Outside
Diameter Length |
Top Cap (Inside Diameter)
/ Style Bot. Cap (Inside Diameter) / Style |
Description & Filter Canister Make |
Unicel
Part Number (not in order) |
Price |
|
4-5/8" 11-7/8" |
2-1/16" / open 2-1/16" / open |
25 sq. ft.
Hayward CX225-RE, American Products Commander II You can also replace with a disposable filter |
C-4325 (replaces C-4327) |
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4-15/16"
4-5/8" |
2-1/8" / open 2-1/8" / open |
Rainbow DSF-35, Waterway Plastics Note: This is a set of 2 cartridges with stick handle on one |
CM-4302B (replaces C-4401) |
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4-15/16"
6-5/8" |
2-1/8" / open 2-1/8" / open |
Rainbow DSF-50, Waterway Plastics Note: This is a set of 2 cartridges with stick handle on one |
CM-4306B (replaces C-4405) |
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4-15/16" 9-1/4" |
2-1/8" / open 2-1/8" / open |
35 sq. ft.
Rainbow, Waterway Plastics, Custom Molded Products You can also replace with a disposable filter |
C-4335 | |
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4-15/16" 11-7/8" |
2-1/8" / open 2-1/8" / open |
32 sq. ft.
Martec, Sonfarrel, Advantage Mfg., Santanna You can also replace with a disposable filter |
C-4332 (replaces C-4430) |
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4-15/16" 13-5/16" |
2-1/8" / open 2-1/8" / open |
25 sq. ft.
Rainbow, Waterway Plastics, Custom Molded Products You can also replace with a disposable filter |
C-4326 (replaces C-4625 & C-4637) |
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Outside
Diameter Length |
Top Cap (Inside Diameter)
/ Style Bot. Cap (Inside Diameter) / Style |
Description & Filter Canister Make |
Unicel
Part Number (not in order) |
Price |
|
4-15/16" 13-5/16" |
2-1/8" / open 2-1/8" / open |
50 sq. ft.
Rainbow, Waterway Plastics, Custom Molded Products You can also replace with a disposable filter |
C-4950 | |
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4-15/16" 14-7/8" |
2-1/8" / open 2-1/8" / open |
28 sq. ft.
Martec, Sonfarrel, Santanna, Cal Spas, Advantage Mfg. You can also replace with a disposable filter |
C-4301 (replaces C-4347 & C-4305) |
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4-15/16" 20-1/8" |
2-1/8" / open 2-1/8" / open |
75
sq. ft. Rainbow RTL-75, Custom Molded Products You can also replace with a disposable filter |
C-4975 | |
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4-15/16" 23-5/8" |
2-1/8" / open 2-1/8" / open |
95 sq. ft. Waterway Plastics, Cal Spas |
C-4995 (upgrade to C-4970) |
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4-15/16" 26-11/16" |
2-1/8" / open 2-1/8" / open |
100 sq. ft. Rainbow RTL-100 | C-4999 | |
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5" 13-5/16" |
2-3/8" / open 2-3/8" / open |
25 sq. ft. Jacuzzi CFR & CFT-25 (in-line) Note: This filter has no plastic center core. |
C-5625 (replaces C-5615 & C-5635) |
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5-3/16" 19-5/8" |
1-1/16" / open 1-5/8" / open |
40 sq. ft. Pacific Marquis Spas |
C-5637 (replaces C-5636) |
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Outside
Diameter Length |
Top Cap (Inside Diameter)
/ Style Bot. Cap (Inside Diameter) / Style |
Description & Filter Canister Make |
Unicel
Part Number (not in order) |
Price |
|
5-11/16" 10-3/8" |
closed w/ string loop 2-1/8" / open |
25 sq. ft. Jacuzzi Whirlpool Bath (front load) |
C-5601 (replaces C-5300) |
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6" 5-1/2" |
semi-circular handle 1-1/2" male thread/ MPT |
25 sq. ft.
top load (Common in Softtubs) |
6CH-25 | |
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6" 8-1/4" |
semi-circular handle 1-1/2" male SAE thread |
45 sq. ft. top load | 6CH-940 | |
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6" 9-1/8" |
semi-circular handle 1-1/2" male thread/ MPT |
47 sq. ft., (Common in HydroSpa & Platinum) | 6CH-47 | |
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6" 10-1/2" |
1-15/16" / open 1-15/16" / open |
30 sq. ft.
Hot Springs Spas/Watkins Mfg. You can also replace with a disposable filter |
C-6430 | |
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6-15/16" 19-3/8" |
3-1/2" / open 3-1/2" / open |
40 sq. ft.
Jacuzzi CF-40 Note: This filter has no plastic center core. |
C-6640 | |
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7" 9-13/16" |
3" / open 3" / open |
25 sq. ft. American, Swimquip Cobra, Premier |
C-7625 (replaces C-7425 & C-7435) |
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7" 9-13/16" |
3" / open w/ molded gasket 3" / open w/ molded gasket |
25 sq. ft. Hayward Star-Clear CX250-RE | C-7626 | |
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Outside
Diameter Length |
Top Cap (Inside Diameter)
/ Style Bot. Cap (Inside Diameter) / Style |
Description & Filter Canister Make |
Unicel
Part Number (not in order) |
Price |
|
7" 19-3/8" |
3" / open 3" / open |
50 sq. ft. Swimquip Cobra Note: Use two of these filters for the 100 sq. ft. Swimquip canister (OAL 38-3/4"). | C-7652 | |
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7" 19-5/8" |
3" / open w/ molded gasket 3" / open w/ molded gasket |
50 sq. ft. Hayward Star-Clear CX500-RE, CX550-RE, CX-570-RE, Muskin P/N 58039, FE-127, Sta-Rite PRC 75 |
C-7656 (replaces C-7455 & C-7477) |
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7-1/2" 14-3/4" |
/ castle 2-1/16" / open |
65 sq. ft.
Sundance Spas Note: Replaces both 7-1/2" & 8" O.D. Sundance cartridges. |
C-7465 | |
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7-1/2" 14-3/4" |
/ castle 2-5/8" / open |
65 sq. ft.
Sundance Spas Note: Replaces both 7-1/2" & 8" O.D. Sundance cartridges. |
C-7466 | |
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8-1/2" 18-1/8" |
/ castle 2-1/2" / open w/ bev. edge |
125 sq. ft. Sundance Spas | C-8320 |
Filter cleaning solution - Filter Fresh concentrate and Minute Rinse filter spray.

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