Types of pool filters and how to choose the best one for your pool

The filter is the true driving force behind water quality: if chosen correctly, the water stays clear, the chemistry is balanced, and maintenance is kept to a minimum. If it’s the wrong size or the wrong type for your setup, you’ll see issues like persistent cloudiness, excessive chemical use, and filtration that never quite works right.

That’s why, when someone is looking for the best pool filters, they don’t need a random list of models: they need criteria to identify which type of filter fits their water volume, pool type, and usage patterns. At Fluidra, through our AstralPool brand, we offer one of the most comprehensive ranges on the market, with models tailored to every need, from family pools to large public facilities.

Why does the filter make all the difference in your pool?

The filter traps suspended particles (organic matter, minerals, and algae) that the pump sends through. Proper filtration ensures the disinfectant works efficiently and that the water quickly regains its clarity after each use.

When the filter is not chosen correctly, two things usually happen:

• Insufficient filtration: the water isn’t purified enough, debris returns to the pool, and chemicals are consumed at an abnormal rate.
• Oversized or wrong type: it generates more pressure than necessary, shortens the pump’s lifespan, and complicates maintenance.

A good filter improves water quality and reduces corrective maintenance—those “emergency solutions” that consume time and products.

Types of pool filters: characteristics and differences

There are three main families of pool filters. Each is based on a different physical principle and has an ideal usage profile.

Sand filters for swimming pools

These are the most common in residential and public facilities. Water passes through a bed of sand (or other equivalent granular media) that traps suspended particles. Their major advantage is simple regeneration: when pressure rises, simply performing a backwash is enough to restore the filter to optimal performance.

They are the dominant choice due to their balance of cost, performance, and durability. They accommodate various filter media that substantially improve the final water quality:

Cartridge filters for swimming pools

Water passes through a polyester or pleated paper cartridge that acts as a physical barrier. They are compact, economical in initial cost, and do not require a backwash system, making them well-suited for residential, above-ground, or in-ground pools with limited space.

• Finer filtration than conventional sand: retains particles as small as 10–15 µm.
• No water waste: no backwashing required; the cartridge is cleaned with a hose.
• Manual maintenance: the cartridge must be removed and cleaned periodically, and replaced every 1–3 seasons depending on usage.

Diatomaceous earth filters

The filter media consists of diatomaceous earth, a fossil-based mineral powder with an exceptionally porous structure. They provide the finest filtration available on the residential market: they retain particles as small as 2–5 µm, invisible to the human eye.

• Superior water quality: water with a clarity that is hard to match with other systems.
• More technical maintenance: diatoms must be replenished after each backwash, and waste must be carefully managed.
• Higher operating cost: DE powder is more expensive than sand or cartridges.

Regenerative Media Filters (FMR)

FMR (Regenerative Media Filters) represent the most advanced technology currently available in the Fluidra range. Unlike conventional filters, the filter media is regenerated mechanically through a controlled vibration process instead of traditional backwashing, offering significant advantages in high-demand facilities such as public swimming pools.

• Exceptional water savings: the regeneration process consumes up to 80% less water than conventional backwashing.
• Superior filtration quality: they retain particles as small as 1–3 µm thanks to the specialized filter media.
• Reduced chemical usage: cleaner water requires less disinfectant dosing.
• Ideal for heated facilities, spas, water parks, and high-traffic public pools.

Filter Comparison by Model and Application

The best choice isn’t “the most expensive filter,” but the one that fits your water volume, your type of facility, and your maintenance habits. This table summarizes the available range:

Comparison by application

Types of filters for above-ground pools: what you need to know

Above-ground pools have their own specific requirements: they are typically compact, are set up and taken down each season, and do not have a utility room.

• Cartridge filter for above-ground pools: The simplest and most common option for small pools (up to 8–10 m³). The unit is compact, requires no backwashing, and there is no need to manage backwash water. Simply remove the cartridge, clean it with a pressure washer, and put it back in place. Ideal for pools up to 10,000 liters with moderate use.
• Sand filter for above-ground pools: Above a certain volume (8–10 m³ or more), the sand filter becomes more efficient than the cartridge. Although it takes up slightly more space, backwashing regeneration is faster, and the filter media lasts for many years. Models such as the smaller-diameter Vesubio or the Artic are common solutions for large above-ground pools.

What filter do I need for my pool? Calculation and selection criteria

To make the right choice, you need to know three key parameters.

Pool volume (m³)

Calculate the approximate volume based on the shape:

• Rectangular: length × width × average depth
• Round: 3.14 × radius² × average depth
• Oval: length × width × average depth × 0.89 (approx.)

Recirculation time

This is the time it takes for the total volume of water to pass through the filtration system. As a general guideline, a complete recirculation cycle is recommended every 8 hours for residential pools and every 4 hours for public pools, although this depends on usage.

Required flow rate

Flow rate (m³/h) = Volume (m³) ÷ recirculation time (h)

Two key points to keep in mind:

• Actual vs. nominal flow rate: the catalog flow rate decreases due to pressure drops and a dirty filter.
• The filter and pump must be properly matched: exceeding the filter’s optimal flow rate does not improve filtration; in fact, it can sometimes worsen filtration and create excess pressure.

How to extend the life of your pool filter

• Backwash or clean the cartridge regularly: overpressure shortens the filter’s lifespan and strains the pump.
• Don’t let it run with the pump dry: check the water level and the valves.
• Replace the filter media when necessary: sand every 5–7 years, glass every 7–10 years, and the cartridge every 1–3 seasons.
• Adjust filtration schedules sensibly: consistent operation at the proper flow rate is usually more effective than “a few hours at full power.”
• Ventilate the equipment room: heat and humidity accelerate equipment wear and tear.
• Preventive maintenance: inspect the system periodically to detect potential leaks or performance losses.

If you want to take it a step further and turn your pool into a truly stable system, Fluidra supports you with solutions and technical expertise to properly size the filter, optimize the hydraulics, and improve the overall efficiency of the system.