When searching for a pool filter there are three main types to choose to keep your swimming pool sparkling clean all year round. These include the cartridge filter, diatomaceous earth (D.E) filter and sand filter.

What is the best pool filter for your swimming pool?

Sand filters and cartridge filters are the most popular of the three because they are small and inexpensive. But which is the best pool filter for you?

The D.E filter offers the best filtration by filtering debris as small as 5 microns. For context, a “micron” is an abbreviated term for “micrometre”, or a millionth of a meter (1/1,000,000 meters). This is about .00004 inches. For size comparison, a human red blood cell is about 5 microns across. A human hair is about 75 microns across (depending on the person).

All filters work in unison with the pool pump by filtering the water before it goes back into the pool. The sand, cartridge and D.E filters are all suitable for small to medium pools and each come with their pros and cons. We’ve listed them below to help you find the best pool filter for your pool.

Sand Filter

  • Smallest in size of the three filters (but quite heavy).
  • The cheapest option upfront.
  • Easy to maintain. The method used to clean the debris out of the sand is called ‘backwashing‘ and it’s easy to do. It can, however, reduce the water level.
  • The sand only requires replacing every 5-8 years.
  • Filters debris 20 – 40 microns (which is the poorest score out of the three filters) so if you have green or cloudy water in your pool a sand filter will take several weeks to clear it compared to the DE filter which will fix it straight away.
  • Suitable for a small pool that isn’t prone to much debris i.e. not directly under a tree and/or infrequently used.

Cartridge Filter

  • The filter of choice for most spas and small above ground pools.
  • Works in the same way that the pleated air filter works in your car by trapping dirt and particles.
  • Can capture debris as small as 10-15 microns.
  • Low impact on the water chemistry
  • Initial purchase and maintenance costs are higher than the sand filter.
  • The cartridges require replacing every 2-4 years.
  • The cartridge filter is not suitable for larger commercial pools.
  • Ideal for any small to medium sized pool.

Diatomaceous earth (D.E) filter

  • Named after the sedimentary rock that is used to filter the water. Diatomaceous earth is composed of chemically inert, fossilized (or skeletal) remains of billions of microscopic algae-like organisms, called diatoms. The D.E filter contains grids inside that are coated with DE powder.
  • DE filters are compact and filter out the smallest particles in comparison to sand and cartridge filters.
  • The filter is backwashed similar to the sand filter, but unlike just backwashing alone, the filter always needs fresh DE powder added.
  • The filter requires replacing every 2-3 years and cleaning every 6 months.
  • The D.E filter is the most expensive option but the best in terms of filtration.
  • Ideal for any pool especially large/commercial swimming pools.

For more advice on pool systems and design, visit the pool section of our Learning Library