Filter Care

When to Clean a Cartridge Filter

A common question that arises with swimming pool cartridge filters is how often one should clean them.  They typical answers range from once a month to every couple of weeks or so, but neither is actually correct.  The correct answer is that a cartridge filter should be cleaned whenever the pressure increases by around 10 PSI or so from its pressured when last cleaned.

For example, imagine you've just cleaned your swimming pool filter cartridge, removing it from its housing and cleaning it thoroughly, and that you checked the pressure gauge afterwards to find it registering 13 pounds.  10 pounds on top of the starting pressure of 13 arrives at 23 pounds of pressure as the level that would indicate it is time to clean your filter.

Cleaning a cartridge filter more often than this is actually slightly disadvantageous.  Pressure in a cartidge builds as the interlocking fibers becomes clogged with small debris.  This combination of debris and interlocking fibers then acts as an increasingly effective filtration medium.  In other words, you are actually filtering water better and better as the filter gets dirty.  Eventually, however, the filter becomes too effective, such that it restricts water flow.  Thus, in maintaining a cartidge filter, you are balancing between water flow and filtration.

Keep in mind that cartridge filters need to be replaced regularly.  For a residential pool with light use and negligible debris entering the pool (screened in or at least minimal foilage) the cartridge should be replaced every year or so.  For pools with heavier demands and spas cartridge filters should be replaced more often than this, even as often as every few months for a system with the heaviest demands.