Pool filter cleaning

The detail, in full

• What this service involves, start to finish

  Sullivan’s cleans cartridge, DE and sand filters on PRESSURE, not on a calendar. Every filter has a clean starting pressure; when the gauge reads about 8–10 psi above it, flow has dropped far enough that the pump is working against the filter and the water is turning over more slowly than the pool needs. In Austin the timing is driven by what is in the air — cedar through December and January, oak pollen in spring, and a heavy bather load all summer — so the same pool can need a clean twice in spring and not again until the fall.

  • Clean starting pressure recorded, so the next clean is judged against this filter rather than a rule of thumb
  • Cartridges pulled and the pleats opened and rinsed individually, not hosed as a block
  • DE grids stripped, cleaned and the correct charge weighed back in
  • Sand backwashed and rinsed, with the media condition reported rather than assumed
  • O-rings, clamps and the pressure gauge itself checked while the housing is open

• How do I know when my pool filter needs cleaning?

  The pressure gauge, read against the filter’s own clean baseline. About 8–10 psi above that number is the point at which flow has fallen enough to matter. A gauge with no recorded baseline tells you nothing useful, which is why the clean pressure is written down at the end of every clean. Weak returns, a cleaner that has slowed and longer run times for the same clarity all say the same thing.

• What is the difference between a cartridge, DE and sand filter?

  What does the filtering, and therefore what cleaning means. A cartridge is pleated fabric that has to be pulled and rinsed by hand. A DE filter coats grids in diatomaceous earth, which is backwashed out and recharged by weight. Sand traps debris in a bed that is backwashed in place and eventually replaced. DE filters the finest, sand is the most forgiving to run, and cartridges sit in between with no backwash water to waste.

• Can a dirty filter make a pool cloudy?

  Yes, and it is one of the more common reasons water refuses to clear when the chemistry reads correctly. Filtration and chemistry are two halves of the same job: chlorine kills what is in the water, the filter removes it. A filter at high pressure is passing less water per hour, so the particles that make water look cloudy stay in it.

These are the questions about pool filter cleaning. Every question we are asked often is answered across the whole site.