It used to be, back in the day, nearly all filter cartridges were made by Unicel and Pleatco. The pleated design was adapted from earlier patents for automotive uses – gas and oil filters, and was in use by the late 60’s, although not in mass production until the early 70’s.
Many OEM cartridges were made by Meissner Mfg. Company, who developed a pleated cartridge from Reemay® polyester, originally developed for the apparel industry by DuPont.
Dick Meissner executed an idea to supply pool dealers with a less expensive filter option for their customers, and Unicel was formed to create generic filter cartridges.
In 1985 Unicel became one of the first to make a business of producing replacement filter cartridges for pools and spas. Before then, your only option was to buy new cartridges from your dealer, who would install an OEM (original equipment manufacturer) cartridge, from Sta-Rite, Swimquip or Purex.
Formed in 1975 by the Kott brothers, holders of several cartridge design patents, Pleatco was purchased in 2006 by two partners who boldly introduced a redesigned core, and a proprietary filter fabric that provides better filtration than Reemay, according to the manufacturer. Pleatco recently introduced a Dual Core filter cartridge, with an internal micro filter.
In 1994, Filbur Mfg Co burst onto the scene, and quickly took spa cartridge market share from Unicel, but found it difficult to gain more shelf space at pool and spa distributorships, who were already carrying both OEM and Unicel cartridges. Filbur makes over 700 Reemay fabric cartridges built to OEM specs, and over 300 Microban® cartridges.
Formed in 1950 by Bud Combest, the oldest company making replacement pool filter cartridges would be Aladdin Equipment Company. Launched in the 90’s, the WorldPool® cartridge is a Reemay cartridge, similar to Unicel and Filbur cartridges. New from Aladdin is the EcoLine cartridge filter, made with recycled plastics, woven into a polyester mesh.
OK, So Which Filter Cartridge Is Best? 
As for Reemay, which has been a standard in cartridge filtration since the sixties, it performs very well under a variety of conditions. The appropriate weight of fabric for pool filtration is a 4 oz fabric, and you may find a 3 oz fabric available, primarily used for low flow spa filtration. Again, a 4 oz cartridge is recommended for most pool systems, 3 oz weight allows too much bypass and clogs easily.
The Pleatco fabric has undergone testing, by the manufacturer, but I’ve not seen any done by independent laboratories. It appears to be a viable option to the Reemay fabric, but is it superior? We think so, which is why we sell Pleatco filters. You can do your own testing – buy a Unicel or Filbur and also buy a Pleatco at the same time. Alternate use of the cartridges and determine what works best with your filter system and your dirt load.
You may find one cartridge that seems to fit better, or load more evenly with dirt, or have longer filter cycles (time between cleanings) than others. However, among the key players making cartridge filters today, you should find them all to be comparable. Keep in mind also, that for many pool filter types there is more than one cartridge available – one of standard filter area and one with more pleats, to add more square footage or filter area into a cartridge of the same size or diimensions.
Is the OEM Filter Cartridge Better?
Generally not, replacement filter cartridges are made to manufacturer specifications – in size, weight and construction. In fact, most pool filter manufacturers don’t make their own filter cartridges, but place a large order with one of the major cartridge fabricators. However, you can be sure, when you buy OEM, that you are buying the best quality pool filter cartridge.
In many instances, some manufacturers like Jacuzzi or Sta-Rite have made cartidge filters with very unique filter cartridges, which only they can sell, especially if they are awarded a patent for the cartridge design.
Filter Cartridges to Avoid?
There are some super generic cartridges that have become available in the last 5 years. Most distributorships and pool stores don’t carry these cheap imports, as they want their customers to be happy, but there are some internet sites that are selling a cheaper pool cartridge, of cheaper construction or materials.
Look for a 4oz polyester fabric, heavy end caps and bands, and a solid internal core. Stick with the major manufacturers, and buy from established websites, and you’ll never have to worry.
Used Pleatco for the first time this year. They fell apart halfway thru the season. Never use another Pleatco filter.