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Pool Filters Explained – Part 5
Part 5: Looking After Your Pool Filter
A quality pool filter is designed to provide many years of reliable service, but like any piece of equipment, it performs best when it is maintained regularly.
Fortunately, filter maintenance is neither difficult nor particularly time-consuming. Small amounts of routine attention can significantly improve water clarity, reduce operating costs and extend the life of both the filter and the wider circulation system.
Perhaps the most important point to remember is this:
A pool filter should be cleaned because it needs cleaning—not simply because a certain amount of time has passed.
Weather, pool usage, surrounding vegetation and water chemistry all influence how quickly debris accumulates.
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Cartridge Filter Maintenance
Cartridge filters require periodic cleaning as suspended debris becomes trapped within the filter element.
Routine maintenance generally involves:
- Turning off the circulation system.
- Relieving pressure from the filter housing.
- Removing the cartridge element.
- Rinsing the pleats thoroughly using a garden hose.
- Inspecting the cartridge for damage.
- Reinstalling the cartridge and restarting the system.
Over time, oils, sunscreen residues, calcium deposits and fine organic material can become embedded within the cartridge fibres.
These contaminants are not always removed by simply hosing the cartridge. Periodic soaking in a cartridge cleaning solution may be recommended to restore filtration performance. Eventually, every cartridge reaches the end of its service life and should be replaced.
Technician’s Tip
If the cartridge remains stained or discoloured after cleaning, this doesn’t necessarily mean it needs replacing. The more important indicators are physical damage, collapsed pleats, tears in the filter fabric or a noticeable reduction in water flow.
Media Filter Maintenance
Media filters use a different maintenance approach.
Instead of removing the media, accumulated debris is flushed to waste during the backwashing process.
During backwashing, water flow through the filter is reversed, lifting and cleaning the media bed before carrying trapped contaminants out through the waste line.
Once backwashing is complete, the filter is normally placed into the rinse cycle for a short period before returning to normal filtration.
The exact procedure varies between manufacturers, so always follow the operating instructions for your specific filter.
When Should You Backwash?
There is no universal schedule.
Backwashing should generally be based on filter performance rather than the calendar.
Common indicators include:
- An increase in filter pressure compared with the normal clean operating pressure.
- Reduced water flow from the return inlets.
- Slower skimmer performance.
- Reduced effectiveness of pool cleaners.
- Cloudy water despite balanced chemistry.
Unnecessary backwashing wastes water and chemicals, while delaying backwashing for too long can reduce circulation and increase strain on the pump.
The Pressure Gauge Is Your Friend
The small pressure gauge mounted on the filter is one of the most valuable diagnostic tools on the entire pool system.
When the filter has been thoroughly cleaned or backwashed, note the pressure reading.
This becomes your clean operating pressure.
Future pressure readings should always be compared with this baseline rather than with someone else’s pool. Changes in pressure often provide early warning that maintenance is required.
Understanding Pressure Readings
High pressure may indicate:
- A dirty filter.
- Restricted water flow through the filter.
- Closed valves.
- Blocked return lines.
- Scale accumulation within the filter.
Low pressure may indicate:
- A blocked skimmer basket.
- A blocked pump basket.
- Air entering the suction line.
- A partially closed suction valve.
- Low water level.
- Pump problems.
Pressure readings should always be interpreted together with the overall behaviour of the circulation system.
The Science Behind It
Pressure itself does not measure how well a filter is cleaning the water.
Instead, it measures the resistance to water flow through the system.
A dirty filter usually produces higher resistance, but pressure can also be affected by pump speed, plumbing design, valve positions and other equipment connected to the circulation system.
This is why pressure changes are generally more useful than the actual pressure value itself.
Common Pool Filter Problems
My water is cloudy even though the filter is running.
Cloudy water is one of the most common pool problems, but the filter is not always the cause.
Possible reasons include:
- Poor water balance.
- Inadequate chlorine.
- Early algae growth.
- Insufficient circulation.
- Short filtration times.
- Worn filter media.
- Dirty cartridge.
- Fine suspended particles following heavy rain.
A systematic diagnosis usually identifies the real cause more quickly than replacing equipment.
Sand is returning to the pool.
If sand is visible around the return inlets, possible causes include:
- Damaged filter laterals.
- A cracked standpipe.
- Incorrect filter media.
- Excessive pump flow.
- Internal damage following incorrect servicing.
This problem generally requires inspection of the filter internals.
My filter pressure keeps increasing quickly.
Rapid pressure increases often indicate:
- Heavy debris loads.
- Early algae growth.
- Fine dust.
- Dead algae following shock chlorination.
- Oils or sunscreen accumulating within cartridge filters.
Cleaning the filter without addressing the underlying cause usually provides only temporary improvement.
My pool still isn’t clear after replacing the filter.
Replacing equipment does not automatically solve water quality problems.
Clear water depends on:
- Correct chemistry.
- Adequate circulation.
- Sufficient filtration time.
- Proper sanitisation.
- Good hydraulic design.
The filter is only one component of the overall system.
Common Myths About Pool Filters
Myth 1 – A bigger pump always means cleaner water.
Not necessarily.
An oversized pump may actually reduce filtration efficiency, increase pressure and waste electricity if it is not correctly matched to the filter.
Myth 2 – Crystal clear water means the pool is healthy.
Not always.
Water can appear perfectly clear while still containing insufficient sanitiser or harmful microorganisms.
Appearance alone should never be used to judge water quality.
Myth 3 – Glass media never needs replacing.
Glass media generally has a long service life, but like all filter media, it eventually becomes less effective and should be assessed periodically.
Myth 4 – Backwashing every week is good practice.
Routine schedules are useful as a guide, but filters should ideally be cleaned according to their operating condition rather than an arbitrary timetable.
Myth 5 – Pool filters remove bacteria.
Filters remove suspended particles.
Sanitisers such as chlorine destroy bacteria, viruses and algae.
The two systems perform different but complementary functions.
Frequently Asked Questions
Which filter provides the clearest water?
All modern filters are capable of producing excellent water clarity when correctly sized, maintained and operated. Differences between systems are often less significant than the quality of the overall circulation and water chemistry.
Should I replace my sand with glass media?
For many pools, glass media can be an excellent upgrade. However, the benefits should be considered alongside the condition of the existing filter, the circulation system and your maintenance practices.
How often should I replace my filter?
The filter housing itself may last many years, but internal components such as cartridges, media, O-rings, pressure gauges and multiport valves may require replacement over time.
Can I install a larger filter than originally recommended?
In many cases, yes—and it may even improve performance. However, equipment selection should always consider the entire hydraulic system rather than the filter in isolation.
Final Thoughts
Pool filtration is one of the most important aspects of maintaining clean, healthy and enjoyable swimming pool water.
While different filter types each have their own advantages, there is rarely a single “best” solution for every pool. The most effective filtration systems are those that have been thoughtfully designed, correctly sized, professionally installed and consistently maintained.
Whether your pool uses a cartridge filter, silica sand, recycled glass or another filtration medium, the principles remain the same. Good circulation, effective filtration, balanced water chemistry and reliable sanitisation work together to create water that is both inviting and safe.
Understanding how your filtration system operates allows you to make better maintenance decisions, recognise problems earlier and maximise the lifespan of your equipment.
If you’re considering upgrading your filter, replacing filter media or simply want to improve the performance of your existing system, taking the time to understand the fundamentals will help ensure your investment delivers years of reliable service.
About SplashCraft
At SplashCraft, we believe informed pool owners make better decisions.
That’s why we’ve created the SplashCraft Insights to provide practical, independent information based on real-world experience servicing residential and commercial swimming pools across Melbourne.
Whether you need advice on selecting the right filter, upgrading ageing equipment or diagnosing a water quality problem, we’re always happy to provide honest, practical guidance tailored to your pool.
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.