Hot tub filter size

How to measure hot tub filter size

Rinse the cartridge first and check the end caps, since Pleatco and Unicel print the part number there. If that number is gone, take measurements in inches, knowing that 1 in equals 2.54 cm.

1. Measure the outside diameter. Take your measurement across the pleats at their widest point. With Pleatco, a measurement may run 1/16 in (1.6 mm) over or under.
2. Measure the length. Measure from one end cap to the other, ignoring any threads or handles. You will get a better result measuring down the middle than along the edge.
3. The top and bottom ends. See whether the ends are open, closed, threaded, or slip fittings, and check for a handle too. If an end is open, measure inside the hole.
4. Type of thread. For a Waterway skimmer, Pleatco offers PWW50P3 featuring a 1-1/2 in SAE thread. The same skimmer also takes PWW50P4, which uses an MPT thread (male pipe thread) sized 1-1/2 in, so it's a different part.
5. Your pleats and tub. Note the model and brand of your tub. Unicel also wants the number of pleats, within 2 either way.

Pleatco filter cross reference: reading the part number

Every Pleatco part number begins with a code identifying the filter or tub manufacturer. PRB stands for Rainbow, PWW is Waterway, and PJ or PJW indicates Jacuzzi. Watkins (Hot Spring) is PWK, Caldera is PCD, and Sundance is PSD. The code PMA stands for Master Spas, PCAL for Cal Spas. Pleatco points out that certain cartridges work with multiple brands.

For most spa codes, the number following the prefix indicates square feet. A PRB50-IN cartridge covers 50 sq ft, while PWK65 covers 65 sq ft. The suffix tells you the thread type:

• P3: SAE thread, 1-1/2 in
• P4: male pipe thread (MPT), 1-1/2 in
• F2S: SAE thread, 2 in
• F2M: male pipe thread, 2 in
• F2L: long male pipe thread, 2 in
• XP4: keyed opening, 1.90 in

Pleatco maintains a record of discontinued numbers and their replacements. PRB37-IN now maps to PRB50-IN, just as PWK45N maps to PWK65. Look up the replacement number before buying if your old cartridge uses a discontinued one.

Unicel filter cross reference: series and upgrades

Unicel organizes cartridges by their outside diameter. The 4000 series spans 4 to 4.99 in, placing C-4950 there at 4-15/16 in. The first digit in these part numbers corresponds to the series. Unicel recommends checking the next series up if your measurement is 4-15/16 or 6-15/16 in.

Codes like 6CH-960 and 8CH-102 contain CH and end in a thread or slip fitting, usually with a top handle. You can swap parts freely if they appear between the same lines in the guide.

Some Unicel items are upgrades that add more pleats to the same shell. C-4950 contains 212 pleats and covers 50 sq ft. The 25 sq ft C-4326 has 106 pleats at the same size, and this unit replaces it. Filbur numbers begin with FC-, and every Filbur product page shows the corresponding Unicel and Pleatco parts.

When should you clean and replace a hot tub filter?

Three steps make up the routine in Jacuzzi's filter care guide. Turn off the tub before removing the filter.

• Weekly: use a hose between the pleats from top to bottom at normal pressure. Fibers can be damaged by a high pressure nozzle.
• Monthly: apply a spa filter cleaner, let it sit for 15 to 20 minutes, then rinse thoroughly. Any cleaner left behind can cause the water to foam.
• Every 3 to 4 months: give it a 12 to 24 hour soak in filter cleaner, then rinse.

Allow it to dry before putting it back, and keep household cleaners and bleach away from it. Keeping a spare with the same part number allows you to swap them while one dries.

About once a year is how often most cartridges need replacing, according to Jacuzzi. Swap it out earlier if you see tears, cracks, or pleats that have gone flat. Replacing the filter does not mean you skip a water change, so see how often to change hot tub water as well. Read more about cloudy hot tub water if the water stays hazy after cleaning.

Common questions