How Pool Filters Work

Understanding how pool filters work will help you make the right selection for you, your budget and your pool.  All filters have their definite benefits, and in some cases, drawbacks.  It’s just a matter of having all the facts and choosing the right pool filter for you.

How pool filters work
During normal operation, water is drawn from the pool using suction created by the pool pump.  The water is drawn into the pump from the main drain and skimmers.  The pool pump generates pressure, circulating water through the pool filter, heater or heat pump, chlorinators or other pieces of equipment, and then filtered water is returned back to the pool.

Properly filtering and sanitizing your pool’s water will keep it healthy and free of debris, bacteria and algae.

Sand Pool Filters: Simple, fool-proof filtration

Sand pool filters extract impurities from the pool water using sand to collect and attract the debris as small as 20 to 40 microns. This is one of the most simple and fool-proof methods of filtering your pool water. In terms of upkeep, these filters are known to last for a decade with very little maintenance. Occasionally, you’ll need to backwash your filter to avoid a build-up of debris or caked sand.

Pros: Simple to operate and maintain.
Cons:  Water, chemicals and heat are lost during backwashing and will not filter out very-fine particles.

D.E. Pool Filters: Best water quality

Diatomaceous Earth (D.E.) is mined and is the fossilized exoskeletons of tiny diatoms. D.E. is used to coat “grids” in the filter housing and acts as tiny sieves allowing for the removal of debris as small as 2-5 microns. Once the water pressure rises, the filter is backwashed, just like a sand filter, and then “recharged” with more D.E. powder.
Pros: D.E. offers the finest level of filtration available delivering the clearest water possible.
Cons:  Water, chemicals and heat are lost during backwashing.

Cartridge Pool Filters – the greenest filtration

Cartridge pool filters are the greenest form of filtration available as they never need to be backwashed.  You’ll never dump thousands of gallons of water into the environment, loosing chemicals and heat in the process. They have a greater surface area than sand allowing for fewer clogs and easier maintenance. They run at lower pressure than sand which puts less backpressure on the pump, providing more flow and water turnover – this also translates into energy savings. Cartridge pool filters should be cleaned once or twice a season by simply hosing the cartridge element off.  Backwashing is NEVER required. Cartridge pool filters trap debris as small as 10 to 15 microns.

Pros: The greenest pool filter available while still offering outstanding filtration and water quality.
Cons:  Upfront costs may be higher than other filter types, but water, chemical and heat conservation more than make up for it.

What pool filter type is right for you?
When considering a new or replacement pool filter, it’s important to know what you need from it and ultimately what is right for you and your pool.  Ask yourself some simple questions. You may answer your own questions more easily than you think.  As always, talk with a Pool Professional to help you make the right decision on your pool’s filter.

  1. Are you in a coastal environment were sand and fine particles will be blown into your pool?
  2. Are you in a northern climate where large leaves, acorns and pine needles are your nemesis?
  3. Do you have color LED pool and spa lighting where only the finest form of filtration will allow the colors to shine?
  4. Do you have a water ban in your area and water conservation is unquestionably most important?
  5. How diligent are you with maintaining your pool’s water chemistry?
  6. Do you heat your pool’s water?


Hayward Cartridge Pool Filters

Hayward DE Pool Filters

Hayward Sand Pool Filters

Tricks and Tips on better water chemistry