How do swimming pool filters work?

Swimming pool filters are essential components of a pool's circulation system, designed to remove dirt, debris, and contaminants from the water to ensure it remains clean and safe for swimming. There are three main types of pool filters: cartridge, sand, and diatomaceous earth (DE) filters.

How Pool Filters Work

1. Water Circulation: The process begins with a pool pump, which pulls water from the pool through the skimmers and main drains. The pump then pushes the water through the filter system25.

2. Filtration Process:

   • Cartridge Filters: Use synthetic fabric or corrugated paper to catch debris. They are cleaned by hosing off and typically need replacement every 1 to 3 years35.
   • Sand Filters: Employ silica sand to trap particles as water flows through the sand bed. They require backwashing to clean the sand and typically filter particles down to 20 microns13.
   • Diatomaceous Earth (DE) Filters: Utilize grids coated with diatomaceous earth powder to filter fine particles, often down to 1-6 microns. Like sand filters, they require backwashing34.

3. Post-Filtration: After filtration, the clean water may pass through additional systems such as a heater or salt chlorine generator before returning to the pool through return jets25.

Key Components and Maintenance

• Pressure Gauges: Monitor the pressure to determine when filters need cleaning or backwashing. A significant increase in pressure indicates the need for maintenance15.
• Multiport Valves: Used in sand and DE filters to facilitate backwashing and rinsing15.
• Filter Replacement: Sand needs to be replaced every 7 to 10 years, while cartridge filters are replaced every few years13.

Overall, pool filters work in conjunction with pool chemicals to maintain water clarity and safety by removing physical contaminants and supporting the chemical balance necessary for healthy pool conditions3.