The cartridge filter is just about the least expensive form of filter there is and also the easiest to maintain. It because
quite unpopular with service guys in the early 80’s because the older ones had dozens of little cartridges and frankly they were a nuisance to clean.
Today’s cartridge filters generally have 4 or fewer cartridges and boast total filter areas of 300 – 500 square feet, thus requiring cleaning less often.
The water enters the filter through the upper bulkhead fitting. It passes through the diffuser which causes it to
circulate evenly around the cartridges. As the water passes through the cartridges , debris in the water is trapped by the filter material. The
cartridges are pleated to allow each cartridge to hold 100 feet or more of filter area. The water exits the cartridges at the bottom and returns to the pool
through the lower bulkhead fitting. No backwash valve is need on this type of filter. A lateral assembly at the bottom of the filter collects
the water and returns it to the pool. The air relief tube serves to continuously remove air pockets from the top of the filter. The air
relief valve offers a way to manually remove an air pocket in the filter.
Today’s cartridge filters filter more finely because the flow rate per square foot of filter material is much less. The
slower the water flows through the filter media, the better it will filter. Cartridge filters remove particulate down to about 20 microns in size.