Pool Filters Explained – Part 2

Part 2: Understanding the Different Types of Pool Filters

Not all pool filters work in the same way, and there is no single filter that is the “best” choice for every swimming pool.

The right filter depends on a combination of factors including the size of the pool, the surrounding environment, the amount of debris entering the water, the sanitising system, available space, water availability, maintenance preferences and, of course, budget.

The good news is that all modern pool filters are capable of producing excellent water quality when they are correctly sized, properly maintained and matched to an efficient circulation system.

Understanding the strengths and limitations of each filter type will help you make a more informed decision.

The Five Main Types of Pool Filters

Australian pool owners are most likely to encounter one of the following filtration systems:

Important: Micron ratings are approximate and should not be used as the sole basis for comparing filters. Actual performance depends on factors such as flow rate, filter condition, water chemistry, media quality and maintenance.

Cartridge Filters

Cartridge filters have become increasingly popular over the past decade, particularly for residential pools.

Instead of using filter media such as sand or glass, cartridge filters use one or more pleated synthetic filter elements. The large folded surface area provides a surprisingly large filtration area within a relatively compact housing.

As pool water passes through the cartridge material, suspended particles become trapped within the fibres while clean water continues back to the pool.

Unlike media filters, cartridge filters are cleaned by removing the cartridge and washing it with a garden hose or specialised cleaning solution.

There is no backwashing process.

Advantages of Cartridge Filters

One of the biggest advantages of cartridge filters is their ability to capture very fine particles. This often results in exceptionally clear water, particularly when combined with good water chemistry and adequate circulation.

Because cartridge filters do not require backwashing, they also conserve water. This makes them particularly attractive in areas where water restrictions apply or where pool owners are conscious of water usage.

Other advantages include:

• Compact design suitable for smaller equipment areas.
• Excellent water clarity.
• No backwashing required.
• Lower water consumption.
• Reduced chemical loss during cleaning.
• Lower operating pressure in many installations.

Disadvantages of Cartridge Filters

While cartridge filters offer excellent performance, they also require more hands-on maintenance.

Eventually the cartridge becomes loaded with oils, sunscreen residues, fine organic material and minerals that cannot simply be washed away with a hose. Periodic chemical cleaning is therefore recommended to restore filtration performance.

The cartridges themselves are also consumable items and will eventually require replacement.

Depending on usage and maintenance, cartridges typically last between one and five years.

Pools surrounded by trees or subject to heavy leaf loads may also require more frequent cleaning and replacement than media filters.

Best Suited For

Cartridge filters are often an excellent choice for:

• Homes without convenient waste drainage for backwashing.
• Residential swimming pools.
• Smaller pools.
• Plunge pools.
• Spa pools.
• Pools where water conservation is important.

Technician’s Tip
A common mistake is cleaning cartridge filters too aggressively with a high-pressure washer. While it may appear to remove more dirt, it can damage the filter fabric and reduce the cartridge’s lifespan. A normal garden hose is usually the safest option, combined with periodic chemical cleaning to remove oils and mineral deposits.

Sand Filters

Sand filters remain one of the most common filtration systems found in Australian swimming pools. Their popularity comes from their simplicity, reliability and relatively low maintenance requirements.

Inside the filter tank is a carefully graded bed of specially manufactured silica sand. As water flows downward through the sand, suspended particles become trapped between the sand grains while clean water continues through the laterals before returning to the pool.

Filtration occurs through a combination of mechanical straining, particle interception and adsorption as water moves through the spaces between individual sand grains.

Interestingly, a slightly dirty sand filter often performs better than a perfectly clean one because the trapped particles help capture even finer debris. Eventually, however, accumulated dirt begins restricting water flow and the filter must be backwashed.

Advantages of Sand Filters

Sand filters have earned their reputation through decades of dependable service.

Their main advantages include:

• Proven, reliable technology.
• Simple operation.
• Low routine maintenance.
• Long media life.
• Suitable for larger pools.
• Excellent durability.
• Lower replacement costs compared with cartridge elements.

The filter media itself usually lasts between five and eight years before replacement is recommended, although actual lifespan depends on water chemistry, usage and maintenance.

Disadvantages of Sand Filters

Although sand filters perform extremely well, they do have some limitations.

Their filtration is generally coarser than a cartridge filter, meaning extremely fine particles may require several passes before being removed from the water.

Backwashing also consumes water and discharges chemically treated pool water to waste.

If backwashing is performed too frequently, water and chemicals are unnecessarily wasted. f it is performed too infrequently, water circulation can suffer due to increased filter resistance.

Finding the correct balance is important.

Best Suited For

Sand filters are particularly well suited to:

• Medium to large family pools.
• Pools with heavy leaf loads.
• Commercial pools.
• Pools with frequent swimmer use.
• Owners seeking simple maintenance.

Glass Media Filters

Glass filter media has become increasingly popular in recent years and is often promoted as a premium alternative to traditional silica sand.

Rather than using natural sand, these filters contain specially processed glass that has been crushed, graded and polished to produce particles with carefully controlled sizes.

From the outside, a glass media filter looks identical to a conventional sand filter. The difference lies entirely in the filtration media inside the tank.

Supporters of glass media suggest it offers several advantages over traditional sand, including improved water clarity, reduced backwashing frequency and lower bacterial growth within the filter bed.

While many pool professionals report positive results, it’s worth recognising that performance depends not only on the media itself but also on correct sizing, flow rate, installation quality and ongoing maintenance.

In other words, changing from sand to glass media will not compensate for an undersized filter, poor circulation or unbalanced water chemistry.

Advantages of Glass Media

Potential advantages include:

• Improved capture of finer particles.
• Reduced backwashing frequency in some installations.
• Lower water consumption over time.
• Long service life.
• Manufactured from recycled materials.
• Good resistance to channel formation when properly maintained.

Possible Limitations

Glass media generally costs more than traditional silica sand.

While many manufacturers advertise significantly superior filtration performance, real-world improvements vary between installations.

For many residential pools, the difference in water clarity may be relatively modest when both systems are correctly maintained.

Best Suited For

Glass media is often an excellent option for:

• New filter installations.
• Premium residential pools.
• Pools where water conservation is important.
• Owners seeking reduced maintenance intervals.

Comparing the Three Most Common Options

The comparisons described above can vary and will be dependent on the operating conditions, the environment, pool contamination and individual pool equipment. The table is provided as a general guide for comparison only.

Technician’s Perspective
After servicing many different pool systems, one lesson becomes clear: the quality of the installation and the correctness of the equipment sizing usually have a greater influence on water quality than the choice between sand, glass or cartridge filtration alone. A correctly sized sand filter that is well maintained will often outperform an undersized cartridge filter, and vice versa. Rather than asking “Which filter is the best?”, a better question is “Which filter is the best fit for my pool?”

Looking Ahead

In the next section, we’ll look beyond the filter housing itself and focus on the filtration media. We’ll explore the differences between silica sand, recycled glass and zeolite, examine how each captures contaminants, discuss common marketing claims, and explain how to maximise the performance and lifespan of your filter through correct media selection and maintenance.

Disclaimer: The information provided in this article is intended as a general guide to help pool owners better understand swimming pool equipment and maintenance. While every effort has been made to ensure the information is accurate at the time of publication, it should not be relied upon as specific technical or professional advice. Every swimming pool is different. Factors such as pool size, construction, equipment configuration, hydraulic design, water chemistry, environmental conditions and how the pool is used can all influence the most appropriate solution. Recommendations that are suitable for one pool may not be appropriate for another. Before purchasing, modifying or replacing pool equipment, or making significant changes to your pool’s operation or water chemistry, we recommend seeking advice from a qualified pool professional who can assess your individual circumstances.

If you would like independent advice on selecting the right filtration system, diagnosing a pool problem or optimising your pool equipment, the team at SplashCraft is always happy to help.