Unicel C-4405 2-Pack | 50 sq ft Rainbow DSF Spa Filter
Excluded Brands
The following brands are not eligible for LTI discount codes (including WELCOME). They go on sale only during manufacturer-authorized promotions:
- Gozney — pizza ovens and accessories
- OHCO — massage chairs
- Positive Posture — massage chairs and recliners
- Nomadix — outdoor lifestyle products (towels, blankets, accessories)
Excluded Products
The following individual products are also not eligible for discount codes:
- Any product that already has a price markdown — items on sale or clearance can't stack additional discounts on top
- FreshWater Salt System Replacement Cartridge (single)
- FreshWater Salt System Replacement Cartridge (3 Pack)
- Route Protection Insurance — third-party shipping protection, not eligible for our discounts
- Bullfrog A / R / X Series 10-00282 Filter Cartridges
- Bullfrog STIL Series 10-00281 Filter Cartridges
- FROG® @ease Sanitizer System for Bullfrog Spas
- FROG® @ease Replacement Cartridge for Bullfrog Spas (3 Pack)
- Bullfrog Simplicity™ Flat Filters for M Series (4 Pack)
- Filter Core Cage & Cap Assembly for Bullfrog Spas
- Fireplaces (gas, wood-burning, and fireplace inserts)
- Electric Fireplaces
- Gas Vent Pipe
- Pellet Vent Pipe
- Fireplace Fronts
This list can change. Manufacturers occasionally add or remove products from their MAP-protected lists. We update this page when they do, but the most accurate way to confirm whether a discount applies to a specific item is to add the item to your cart and try the code at checkout. If the code doesn't work, the item is excluded. If it does work, it's eligible.
The Unicel C-4405 is a matched pair of replacement filter cartridges delivering 50 square feet of combined filtration for Pentair Rainbow Dynamic Series IV systems and Waterway skim filters. It is sold as a set of two because the system is designed around two cartridges working side by side — not because two is a convenient bulk quantity.
That distinction matters more than it might sound. These housings run a pair of compact cartridges in parallel rather than one large one, and the 50 square foot rating you see on the system — Rainbow designates it DSF-50 — describes what both cartridges deliver together. Each individual cartridge accounts for roughly half. If you have seen the equivalent aftermarket part listed as a "25" and wondered whether you were being sold something smaller, you were not: the number simply refers to one cartridge instead of the pair. Both figures describe the same hardware.
The practical consequence is that these two cartridges live and die together. Water entering the housing splits between them and takes whichever path offers less resistance. Put a fresh cartridge next to a used one and flow skews hard toward the new one, which then loads up at an accelerated rate while the old cartridge does progressively less work. The system never reaches its rated capacity, and the new cartridge wears out well ahead of schedule. Replacing as a set is not an upsell — it is how the design is meant to function.
Each cartridge measures a compact 4-15/16" across by 6-5/8" long, with open 2-1/8" ends carrying molded lip seals — the raised sealing edge that presses against the housing and blocks unfiltered water from slipping around the outside of the media. Construction is Unicel's standard: pleated polyester Reemay media over a solid molded core, with chemical-resistant end caps built to an exact OEM fit. Made in the USA by Meissner Manufacturing, with more than 45 years behind the Unicel name.
Pro Tip: Always install both cartridges at the same time, and never pair a new one with a cartridge that has been in service. It is tempting to swap only the one that looks worse, and it consistently backfires. Flow follows the path of least resistance straight to the clean cartridge, so the new one absorbs a disproportionate share of the load and clogs early while the old one coasts. You end up buying cartridges more often than if you had simply replaced both at once. This is also a good argument for keeping a spare set on hand.
UNICEL®
UNICEL® Brand FAQs
Who makes Unicel filters?
Unicel filters are made byMeissner Mfg. Co., Inc., a family business that began as a small contract sewing operation in thelate 1950sand moved into pool filtration through the 1970s. By the end of that decade the company was producing cartridge filters for the industry'soriginal equipment manufacturers, and in1985it introduced the Unicel brand as aftermarket replacements. It's still owned and operated by the Meissner family today.
Are Unicel filters as good as the original manufacturer's filter?
Unicel builds its cartridges tomeet or exceed original equipment specifications— and that's a meaningful distinction here, because the company produced cartridges for the industry's OEMs before it ever launched its own brand. Unicel cartridges usedurable, chemical-resistant end capswith an exact fit,high-capacity media,uniform pleatsfor optimal flow, and asolid corethat resists collapsing under pressure.
Where are Unicel filters made?
Unicel filters are manufactured inCalifornia, with components sourcedexclusively in the United States. The line comprisesnearly 500 products, covering replacement cartridges, D.E. grids, filter discs, and related parts.
How do I find the right Unicel filter for my spa?
Unicel cartridges areinterchangeable with all major filter brands, and each one cross-references to a list of original equipment part numbers. The most reliable method is topull your current cartridge and read the part number printed on it, then match it to the Unicel cross-reference. If the number has worn off,measure your old cartridge— diameter, length, and the size and style of the openings at each end — and match those instead. Also confirmhow many cartridgesyour spa uses.
How long does a Unicel filter last?
Cartridge life depends on how heavily the spa is used, yourwater chemistry, and how consistently you clean the filter. Many Unicel cartridges useReemay® polyester media, whosetrilobal fibersprovide considerably more surface area than standard rounded fibers — which increases dirt-holding capacity and extends the time between cleanings. With regular rinsing and periodic deep cleaning, a well-maintained cartridge commonly serves a year or more.
When should I replace my filter instead of cleaning it?
Replace the cartridge when thecycle between cleanings becomes noticeably shorter, when you seelow water flowor high differential pressure, when the media has atear, or if thecenter core collapses. Pleats that stay permanently flattened or discolored after a proper cleaning are another sign the cartridge has reached the end of its service life.
About UNICEL®
Unicel is the nation's leading manufacturer of replacement filter cartridges for pools and spas — and the story behind it is a genuinely American one. In the late 1950s, Richard T. Meissner started a small part-time contract sewing operation. Through the 1970s, Meissner Mfg. Co., Inc. moved into swimming pool filter bags, then D.E. grid element covering, and by the end of that decade the company was producing cartridge filters for the industry's original equipment manufacturers.
That's the detail that matters most: Unicel was building the filters that went into new spas long before it sold a replacement. In 1985, the company introduced the UNICEL brand so dealers and technicians could source elements built to O.E.M. specifications from a single place — even for equipment brands they didn't carry. Today the line spans nearly 500 products, all manufactured in California with components sourced exclusively in the USA.
By staying focused on one thing — filtration — Unicel has built deep expertise in a critical corner of the industry, from media development to cartridge design. Every cartridge is built with chemical-resistant end caps for an exact fit, high-capacity filter media, uniform pleats for optimal flow, and a solid core that holds its shape under pressure. Meissner Mfg. Co., Inc. remains owned and operated by the Meissner family, still recognized for quality and service. American-made products, world-class service.
