Pool Filter Replacement: A Complete Guide to Cartridge Systems and Maintenance
Andrew
April 10, 2025
Understanding Pool Filtration Types and How Pool Filter Cartridges Work
Pool and spa owners have three main filtration options: sand, diatomaceous earth (DE), and cartridge filters. Sand filters use specially graded sand to trap particles down to about 20–40 microns and require regular backwashing. DE filters offer the finest filtration (capturing particles as small as 2–5 microns) but involve more complex maintenance and use potentially hazardous powder. Cartridge filters strike an excellent balance, effectively filtering a range of particulate matter while requiring no backwashing and minimal maintenance, making them increasingly popular for both pool and spas.
The Cartridge Filtration Process
Pool filter cartridges are cylindrical components consisting of pleated polyester material with plastic end caps. Their design creates an extensive surface area—often 50–200 square feet—that efficiently traps contaminants. As your pump circulates water through the filter housing, water flows from outside the cartridge inward, with the pleated material capturing oils, dirt, hair, and particles along the way. Pool filter cartridges are the unsung heroes of water clarity, trapping debris and contaminants that chemicals alone can't address. This mechanical filtration works alongside your chemical treatments to maintain water clarity and safety, with the debris remaining trapped in the pleats until the filter is removed for cleaning.
The Cartridge Filtration Process
Pool filter cartridges are cylindrical components consisting of pleated polyester material with plastic end caps. Their design creates an extensive surface area—often 50–200 square feet—that efficiently traps contaminants. As your pump circulates water through the filter housing, water flows from outside the cartridge inward, with the pleated material capturing oils, dirt, hair, and particles along the way. Pool filter cartridges are the unsung heroes of water clarity, trapping debris and contaminants that chemicals alone can't address. This mechanical filtration works alongside your chemical treatments to maintain water clarity and safety, with the debris remaining trapped in the pleats until the filter is removed for cleaning.
Pool filter cartridges are the unsung heroes of water clarity, trapping debris and contaminants that chemicals alone can't address.
Benefits of Cartridge Filtration
Unlike sand filters that require backwashing (wasting 100–300 gallons of water each time), cartridge filters are more environmentally friendly and energy-efficient. They operate at lower pressure, reducing strain on your pump, and can filter out smaller particles than many alternative systems. Quality cartridge filters with fine pleated polyester media provide superior filtration for both in-ground and above-ground pools and spas.
Unlike sand filters that require backwashing (wasting 100–300 gallons of water each time), cartridge filters are more environmentally friendly and energy-efficient. They operate at lower pressure, reducing strain on your pump, and can filter out smaller particles than many alternative systems. Quality cartridge filters with fine pleated polyester media provide superior filtration for both in-ground and above-ground pools and spas.
Signs It's Time for a Pool Filter Replacement
Many manufacturers recommend replacing pool filter cartridges every 1–2 years, but actual timing of when to replace a pool filter depends on several factors including pool usage, local environment, and maintenance practices. For example, it is likely that a year-round pool or spa will need more frequent cleaning and replacement than a pool only open seasonally. Watch for these possible signs that your cartridge needs replacement:
Decreased water flow: When your filter can no longer be cleaned effectively, you'll notice reduced water flow from return jets, slower skimming action, or longer run times needed to maintain clarity.
Persistent pressure issues: If pressure gauge readings remain higher than normal for your pump, even after thorough cleaning, the cartridge has likely reached the end of its useful life.
Physical damage: Inspect your cartridge for torn pleats, cracks in end caps, or collapsed bands. Once the structural integrity is compromised, replacement is necessary regardless of age.
Stubborn staining: Cartridges with brown, gray, or green staining that don't respond to cleaning solutions have likely absorbed oils and minerals that cannot be removed.
Frequent cleaning: When you find yourself cleaning the filter every couple of weeks instead of months, it's usually more cost-effective to replace the cartridge.
Decreased water flow: When your filter can no longer be cleaned effectively, you'll notice reduced water flow from return jets, slower skimming action, or longer run times needed to maintain clarity.
Persistent pressure issues: If pressure gauge readings remain higher than normal for your pump, even after thorough cleaning, the cartridge has likely reached the end of its useful life.
Physical damage: Inspect your cartridge for torn pleats, cracks in end caps, or collapsed bands. Once the structural integrity is compromised, replacement is necessary regardless of age.
Stubborn staining: Cartridges with brown, gray, or green staining that don't respond to cleaning solutions have likely absorbed oils and minerals that cannot be removed.
Frequent cleaning: When you find yourself cleaning the filter every couple of weeks instead of months, it's usually more cost-effective to replace the cartridge.
A clogged filter forces your pump to work harder, increasing energy consumption and potentially shortening equipment lifespan.
The true cost of delayed replacement goes beyond cloudy or murky water. A clogged filter forces your pump to work harder, increasing energy consumption, and potentially shortening equipment lifespan. Considering many pool owners run their filters for 16 or more hours a day, it's easy to understand why a clean filter and efficient pump operation are critical. More importantly, inadequate filtration can lead to water quality issues that require expensive chemical treatments or even pool draining to start all over.
Choosing the Right Replacement Pool Filter Cartridge
Finding the correct replacement filter begins with identifying your current model. Determining what pool filter cartridge you need is typically easy. If you're not sure, most filter cartridges include identifying information on the end cap or band. If you don't have one, measure the filter housing.
Measuring for Compatibility
Thanks to a range of standard dimensions, premium replacement cartridges are designed to fit multiple manufacturer housings. For example, quality pleated polyester filter cartridges are available from Hayward, Pentair, Intex, Pleatco, and many other brands. As there may be variability in square footage, it is useful to know the surface area in square feet of your filter. A larger pool can clog a filter with less surface area more quickly, even if the filter is otherwise compatible with your housing. When in doubt, cross-reference by both model number and measurements.
You'll need four key measurements:
The composition and construction of filter media significantly impact performance and longevity. Premium cartridges often feature point-bonded pleated polyester, which should maintain structural integrity through multiple cleanings, though all cartridges will need to be replaced eventually, and many pool owners choose replacement over the sometimes time-consuming process of cleaning filters. The density and arrangement of pleats also play crucial roles—more pleats per inch increase surface area (measured in square feet) and dirt-holding capacity, though too tight pleating can restrict water flow. When evaluating replacements, focus on total filtration area rather than micron ratings of different cartridges—especially considering most manufacturers don't display microns given the focus on overall filtration efficiency.
To summarize, quality replacement cartridges may feature:
Measuring for Compatibility
Thanks to a range of standard dimensions, premium replacement cartridges are designed to fit multiple manufacturer housings. For example, quality pleated polyester filter cartridges are available from Hayward, Pentair, Intex, Pleatco, and many other brands. As there may be variability in square footage, it is useful to know the surface area in square feet of your filter. A larger pool can clog a filter with less surface area more quickly, even if the filter is otherwise compatible with your housing. When in doubt, cross-reference by both model number and measurements.
You'll need four key measurements:
- Length (from end cap to end cap)
- Outside diameter
- Inside diameter (of the center hole)
- Square footage (media filtration area) — typically determined by volume of pool or spa at time of installation
The composition and construction of filter media significantly impact performance and longevity. Premium cartridges often feature point-bonded pleated polyester, which should maintain structural integrity through multiple cleanings, though all cartridges will need to be replaced eventually, and many pool owners choose replacement over the sometimes time-consuming process of cleaning filters. The density and arrangement of pleats also play crucial roles—more pleats per inch increase surface area (measured in square feet) and dirt-holding capacity, though too tight pleating can restrict water flow. When evaluating replacements, focus on total filtration area rather than micron ratings of different cartridges—especially considering most manufacturers don't display microns given the focus on overall filtration efficiency.
To summarize, quality replacement cartridges may feature:
- Reinforced bands to prevent pleat collapse
- Antimicrobial treatments to prevent bacteria growth
- End caps that create proper seals without leakage
- Dense, uniform, and appropriately spaced pleating
By investing in a quality replacement filter cartridge, you're not just helping to ensure clear water—you're protecting your entire pool system. Remember that manufacturer recommendations about compatible filters aren't always your only option; many premium aftermarket cartridges offer equal or superior performance at competitive prices.
Regular filter replacement is one of the simplest yet most effective ways to maintain your pool's health, reduce chemical usage, and extend the life of your equipment. With proper selection and timely replacement, you'll enjoy cleaner, clearer water with less effort and expense.
Regular filter replacement is one of the simplest yet most effective ways to maintain your pool's health, reduce chemical usage, and extend the life of your equipment. With proper selection and timely replacement, you'll enjoy cleaner, clearer water with less effort and expense.
