For over 25 years All Clear has serviced between 500 an 1200 pools a week and during that time, cartridge filtration has become the number one selling filter media in the country for swimming pool filtration. During this time we have become an expert on these types of systems. I will explain how long filtration cartridges should last and why they need changing.
Cartridges are rated at 20 microns of filtration. That test was done in the late 1970's by putting a 100 gallons a minute through a 100 sq ft. filter so that rating is when we put one gallon per minute per sq. foot of media. The industry has made larger and larger filters in order to increase the length that a cartridge will last and to increase the filtration down to as low as 1 micron (EG: a starite 450 filter running at 3 psi, and 50 gpm.)
There are several ways to know if a cartridge filter needs replacement:
For every 10 pounds of pressure rise on the system, the flow in gallons per minute can drop by as much as 30% so we will not have consistent flow (which causes the sweep to stop working and algae will form) and the higher pressure can cause damage to the filter manifolds and other internal parts.
What shortens a cartridge's lifetime: