How to Replace a Pool Filter Safely

The Short Version

• Cut power completely: Switch off the circulation pump at the main electrical breaker so the motor cannot kick on unexpectedly while your hands are on the equipment.
• Release all pressure: Open the air relief valve (the small knob on top of the tank that lets out trapped air) and wait until the round pressure dial drops to zero before touching any clamps.
• Swap and seal: Open the housing, lift out the old cartridge (the pleated cylinder that catches dirt), clean the tank belly, and lubricate the rubber sealing ring with silicone grease.
• Bleed air on restart: Keep the air knob open when you restart the motor, stand clear of the tank lid, and close the valve only when a steady stream of water shoots out.

Shutting Off Power and Relieving Pressure Safely

Working on a pool filter requires complete respect for water pressure. A sealed filter housing can hold significant pressure when running. If you loosen a clamp while that force remains trapped inside, the heavy plastic lid can fly off violently. This can shatter nearby PVC plumbing or cause serious personal injury. Taking two minutes to shut down the system properly prevents equipment damage and keeps you completely safe.

1. Cut the electrical power at the circuit breaker. Do not simply turn off the pump using an automated smartphone app or a mechanical dial timer. Timers can cycle back on automatically, and mobile software can glitch. Walk to your electrical sub-panel or main breaker box and flip the switch to off. If your pool pump plugs into an outdoor GFCI outlet (a protected ground-fault outlet with a weatherproof cover), unplug the heavy cord directly from the receptacle.
2. Inspect the pressure gauge. Look closely at the pressure gauge (the round dial on top of the tank that shows water pressure). While the pump is running, this dial typically reads between 10 and 20 pounds per square inch. When the pump stops, the dial should begin to drop, but trapped air pockets can maintain dangerous force inside the dome.
3. Open the air relief valve. Find the air relief valve (a small knob or lever located on top of the tank next to the gauge). Turn this knob counter-clockwise by hand. You will immediately hear a loud, sharp hissing sound as pressurized air shoots out of the small port. Keep your face and eyes angled away from the opening so mist or debris does not blow into your eyes.
4. Wait for water to emerge. Keep the relief valve open until the hissing sound fades out completely and a solid trickle of pool water runs down the side of the tank. Look back at the round pressure dial. Confirm that the needle sits firmly against the zero mark. Never attempt to loosen a clamp or turn a locking ring until the needle rests on zero.
5. Close your plumbing shut-off valves. If your equipment pad sits below the waterline of the pool, gravity will push water backward through the pipes while the housing is open. Turn the intake and return handles to the closed position to prevent pool water from flooding your yard while you work. If you are doing late-season maintenance, you can also review how to protect your pool pump in winter to keep plumbing lines safe from freezing temperatures.

How to Measure and Pick the Right Replacement Filter

A pool filter cartridge is a cylindrical core wrapped in pleated fabric that strains fine particles out of the water. Over several seasons of catching body oils, sunscreen, dust, and fine silt, the fabric fibers become compacted and permanently clogged. Routine hose rinsing stops lowering the tank pressure, signaling that the material has reached the end of its working life. To get water flowing freely again, you need an exact replacement match that fits snugly inside your housing.

The fastest way to identify your replacement element is to look at the hard rubber end caps on your old cartridge. Manufacturers typically mold the part number directly into the plastic rubber on the top or bottom rim. If the lettering has degraded from exposure to pool sanitizers, you can easily gather three physical measurements using a standard tape measure:

• Outside diameter: Measure directly across the widest circular top of the cartridge from outer edge to outer edge. Small above-ground pool filters typically measure around 4 to 5 inches across, while large in-ground systems measure between 7 and 9 inches across.
• Total length: Lay the cartridge flat and measure from the outer surface of the top plastic end cap down to the outer surface of the bottom end cap. Do not include extended molded handles or raised locating nubs in this length unless the original brand specification calls for them.
• Center hole openings: Measure the inside diameter of the opening on both ends. Some cartridges have open round holes on both the top and bottom to slide over internal pipes. Others feature an open hole on the bottom and a solid molded handle on the top.

Pay close attention to the listed surface area of the fabric, which is marked in square feet. A 100-square-foot filter and a 120-square-foot filter might share similar outer dimensions, but the larger unit packs significantly more pleats around the center core. Matching your exact pump flow rate and housing size prevents water from slipping past loose seals without being filtered.

Opening the Tank and Swapping the Filter Element

Once the pressure dial reads zero and the water valves are closed, you can open the housing. Take your time during this step to avoid stripping metal hardware or gouging the plastic lip where the two halves meet.

1. Remove the tank drain plug. Locate the threaded drain plug at the very bottom base of the filter tank. Twist it counter-clockwise and pull it out. Allowing the standing water inside the tank to drain onto the ground lightens the housing and carries away heavy grit that settled at the bottom.
2. Loosen the belly band or locking collar. On small above-ground cartridge systems, the lid is held by a large threaded locking ring that you twist counter-clockwise by hand. On larger in-ground systems, a heavy metal clamp band wraps around the center seam, held tight by a long brass bolt and heavy spring. Use a socket wrench to loosen the brass nut. Back the nut off until the spring loosens completely and the metal clamp pulls free from the tank rim.
3. Lift off the top housing dome. Carefully wiggle the top lid back and forth to break the suction seal. Never jam a flathead screwdriver or metal pry bar into the seam between the two halves. Metal tools will scratch or crack the plastic lip, leading to persistent leaks that cannot be fixed with a new seal. If the lid feels stuck, tap the side gently with a rubber mallet or the palm of your hand until the seal releases, then lift the lid straight up.
4. Pull the old cartridge straight out. Lift the dirty cylinder out of the lower tank body. If your filter uses a multi-cartridge cluster, first lift off the top plastic manifold that connects the elements together, then remove each cartridge one at a time. Old filters can be heavy because trapped silt and wet fabric hold gallons of water.
5. Wash out the lower tank belly. Take a garden hose and spray down the inside walls and base of the lower tank. Flush all settled dirt, hair, and sand out through the open bottom drain port. Once the tank floor is spotless, screw the drain plug back into the base hand-tight.
6. Slide the fresh cartridge into position. Lower the new replacement cylinder into the housing. Make sure the open hole on the bottom aligns squarely over the raised guide pipe at the bottom of the tank. Press down firmly with both hands until the cartridge sits level and secure on its base. For multi-element units, place the top guide manifold back over the upper openings, making sure every cylinder seats into its matching port.

Inspecting and Lubricating the Rubber Sealing Ring

The O-ring (the thick rubber sealing ring that prevents leaks between the tank halves) keeps high-pressure water inside the housing. If this ring pinches, cracks, or dries out, water will spray out around the belly band the moment you turn the pump back on. Follow this quick inspection checklist every single time you open the filter:

• Remove and stretch the rubber ring: Lift the rubber sealing ring completely out of its plastic channel. Bend the rubber between your fingers every few inches, checking for tiny hairline cracks, flattened spots, splits, or rough dry patches. If the rubber feels brittle or stiff, discard it and install a fresh ring.
• Wipe the seating channel clean: Use a clean microfiber cloth to wipe out the groove where the ring rests. Remove all accumulated dirt, dead algae, and hard water scale. Even a tiny grain of sand trapped beneath the rubber ring can create a pressurized spray.
• Coat with silicone pool lubricant: Squeeze a nickel-sized amount of silicone-based or Teflon-based pool lubricant onto your fingers. Rub a smooth, even film around the entire circumference of the ring until it looks glossy. Lubrication prevents the rubber from pinching or dragging when the clamp tightens.
• Avoid petroleum jelly: Never use household petroleum jelly or motor oils on pool rubber. Petroleum products break down synthetic rubber compounds, causing the ring to swell, soften, lose its shape, and fail within a few weeks.
• Seat the ring flat: Press the slick ring back into its clean channel. Run your index finger around the entire loop to confirm that the rubber sits flat without any twists or bunched sections.

Restarting the Pump and Bleeding Out Remaining Air

Reassembling the tank and restarting the circulation pump requires methodical care. The empty filter housing currently holds cubic feet of air that must be pushed out before full water circulation can resume.

1. Reinstall the tank lid and clamp band. Place the upper dome straight down over the lower base, making sure the rubber ring stays flat in its groove. Position the metal clamp band around the center lip. Tighten the brass bolt with your socket wrench. As the nut tightens, tap around the outside of the metal band with a rubber mallet to help the clamp seat evenly. Continue tightening until the coils on the tension spring press firmly together according to the guide on the tank label.
2. Ensure the air relief valve is open. Verify that the small knob on top of the dome remains turned to the open position. Never start a circulation pump with a closed relief valve after opening the tank.
3. Reopen all plumbing valves. Open your suction intake valves and pool return lines. Check the clear lid on your pump strainer basket to ensure the pot holds water to prime the motor.
4. Stand clear and restore power. Walk over to your circuit breaker panel or switch box. Stand to the side of the equipment, well clear of the filter dome lid, and flip the breaker on. The motor will begin humming and pulling water into the system.
5. Bleed the trapped air. As water enters the filter housing, it forces trapped air upward. You will hear a loud rush of air blowing out through the open relief valve, and air will churn out of the pool return jets. Stay clear of the tank while this air purges.
6. Close the valve on a solid stream. The moment water begins shooting out of the relief valve port in a steady, continuous stream without sputtering air, turn the knob clockwise to close it tight.
7. Record your clean baseline pressure. Look at the round dial on the pressure gauge. The needle will settle at your clean operating baseline, typically between 8 and 15 pounds per square inch depending on your plumbing layout. Use a water-resistant marker to write this starting number on the side of the tank. When your pressure rises 8 to 10 pounds above this clean starting mark, you will know the pleats are full of dirt and require service. Maintaining clear water also depends on chemistry, so take time to review how to measure chlorine in a pool for safe swimming alongside your fresh filtration schedule.

Choosing the Right Replacement Tools and Accessories

Keeping your filtration system running smoothly depends on pairing the right physical parts with practical protective accessories. When shopping for replacement filter cartridges, look for heavy-duty polyester or trilobal filtration fabrics. These fabrics feature sharp, diamond-shaped fibers that catch fine dirt particles across a larger surface area than flat woven paper, keeping water clear for longer stretches.

You can also protect your new cartridge from premature clogging by using pre-filter skimmer socks. These elastic mesh nets stretch over your pool skimmer baskets to catch hair, pine needles, bugs, and coarse yard debris before anything enters the underground plumbing. This basic layer of protection keeps heavy muck away from your filter pleats, significantly extending the time between manual cleanings.

Before purchasing replacement elements, verify the exact model number of your filter housing rather than guessing based on pool gallons alone. Check the outer diameter, height, and core opening dimensions against your equipment manual. Selecting elements built with durable plastic core supports and reinforced end caps ensures your filter can withstand high flow rates without collapsing inward under pressure.

1

Intex Type A Filter Cartridge for Pools, Twin Pack, 1

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  9.4
• Brand
  Intex

Key specs2

Cartridge Dimensions

8.5 in height by 4.2 in width

Pump Compatibility

• Intex Krystal Clear 28603EG
• Intex Krystal Clear 28637EG
• Intex Krystal Clear 28635EG

Pros & cons43

Pros

• Fits common Intex pump models including 28603EG, 28637EG, and 28635EG
• Dacron paper pleats rinse clean easily with a standard garden hose
• Includes two replacement cartridges in a single package
• Simple drop-in sizing requires no tools or adapters during filter swaps

Cons

• Needs replacement every two weeks according to manufacturer guidelines
• Limited to small above-ground pump setups and cannot fit large inground tanks
• Does not fit systems requiring larger Type B or commercial cartridge sizes

2

POOLPURE PCC105-PAK4 Replaces Pentair CCP420, 178584, Ultral-A6, Unicel C-7471, 817-0106,

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  9.4
• Brand
  POOLPURE

Key specs2

Safety Certification

NSF/ANSI 50 certified by IAPMO

Filter Media Specs

Features 105 square feet of trilobal fabric per cartridge with 3-inch top and bottom core openings.

Pros & cons53

Pros

• Large 105 square foot filtration area per cartridge captures heavy dirt loads
• Certified by IAPMO against NSF/ANSI 50 standards for material safety
• Trilobal fabric design offers three times the surface area of standard media
• Replaces cartridges in large systems like Pentair Clean and Clear Plus 420
• Dirt-locking pleat structure rinses clean for repeated use before replacement

Cons

• Requires a large pressure tank with at least 26 inches of vertical clearance
• Sized specifically with 3-inch openings and will not fit 4-inch manifolds
• Multi-cartridge set requires careful alignment on internal tank manifolds

3

POOLPURE PLF120A Pool Filter Replaces Hayward C1200, CX1200RE, Pleatco PA120,

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  9.4
• Brand
  POOLPURE

Key specs2

Particle Filtration Level

50 microns

Single Cartridge Sizing

Measures 23 1/4 inches long by 8 15/16 inches wide with 4-inch open ends for single-cartridge tanks.

Pros & cons53

Pros

• Provides 120 square feet of media area in a single large cartridge
• Captures fine particles down to 50 microns including dust, pollen, and sand
• Certified by IAPMO against NSF/ANSI 50 material safety standards
• Direct replacement for Hayward Star Clear Plus C1200 and CX1200RE housings
• Trilobal fabric structure releases debris easily when rinsed with water

Cons

• Wide 4-inch top and bottom openings will not seat on smaller 3-inch pipe cores
• Bulkier 8 15/16-inch diameter makes handling heavy when saturated with water
• Recommended cleaning interval is every two weeks under regular pool use

4

IMPRESA 20-Pack of Pool Skimmer Socks - Excellent Savers for

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  9.0
• Brand
  IMPRESA

Key specs2

Basket Service Interval

Replace every 4 to 8 weeks

Chemical Restriction

Do not dissolve chlorine tablets directly inside the basket because concentrated chemicals erode the nylon.

Pros & cons53

Pros

• Ultrafine nylon mesh catches hair, oil, pollen, and bugs before reaching the tank
• Protects the main filter cartridge from rapid clogging and heavy debris buildup
• Elastic edge stretches over inground and above-ground skimmer baskets
• Pack of 20 socks allows easy disposal or multiple wash cycles
• Reduces how often you have to open the pressurized filter tank for cleaning

Cons

• Chlorine tablets placed in the skimmer basket will erode the nylon fabric
• Requires checking every few days to prevent clogged flow from choking the pump
• Must be replaced every 4 to 8 weeks as the elastic and mesh wear out

5

Black Diamond Stoneworks Ultimate Spa Filter Cleaner Fast-Acting Spray for

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  9.0
• Brand
  Black Diamond Stoneworks

Key specs2

Cleaning Contact Time

5 minutes

Targeted Buildup

• Body oils and suntan lotion
• Grease and organic scum
• Pleated fabric grime

Pros & cons43

Pros

• Fast spray formula dissolves grease and suntan oils in just 5 minutes
• Eliminates the need for overnight soaking buckets during cartridge maintenance
• Residue-free chemistry prevents foaming issues when the cartridge returns to water
• Safe for all pleated cartridge fabrics across hot tubs, spas, and pools

Cons

• Spray application requires thorough manual hose rinsing to dislodge loose grime
• One-quart bottle may run out quickly if cleaning large inground multi-cartridge sets
• Formulated for oily scum and organic buildup rather than heavy calcified scale

6

U.S. Pool Supply 4 Pack of Universal Replacement Filter Cartridges,

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  9.0
• Brand
  U.S. Pool Supply

Key specs2

Pump Flow Range

530 to 2,000 GPH

Multi-Brand Fit

Replaces Intex 59900E and 29000E cartridges while also fitting Bestway and Summer Waves above-ground pumps.

Pros & cons53

Pros

• Collapse-resistant hard plastic center core maintains shape under pump suction
• Fits multiple brands including Intex, Bestway, and Summer Waves pump systems
• Universal sizing covers Type A, Type C, and Type III filter specifications
• Four-pack bundle provides several swap cycles for routine two-week maintenance
• Washable polyethylene terephthalate fibers rinse clean between full replacements

Cons

• Flow rating is limited to small pumps moving between 530 and 2,000 gallons per hour
• Center opening of nearly 2 inches does not seal correctly on large 3-inch pipes
• Requires frequent replacement every two weeks under regular swimming conditions

7

INTEX 28637EG C1000 Krystal Clear Cartridge Filter Pump for Above

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  8.8
• Brand
  Intex

Key specs2

Manufacturer Warranty

2-year limited warranty

Water Flow Rates

• 1,000 GPH pump flow rate
• 750 GPH system flow rate
• Suited for pools up to 6,000 gallons

Pros & cons53

Pros

• Complete pump and housing assembly provides a 1,000 GPH pump flow rate
• Built-in HydroAeration technology improves water circulation and clarity
• Simple hose connections fit standard 1.25-inch diameter pool fittings
• Comes backed by a 2-year manufacturer warranty for equipment protection
• Uses common Type A replacement cartridges that swap out without special tools

Cons

• Limited to above-ground pools holding up to 6,000 gallons of water
• Not compatible with large 1.5-inch or 2-inch plumbed inground pool piping
• Cartridges inside the housing still require replacement every two weeks

8

IMPRESA 10-Pack of Pool Skimmer Socks - Excellent Savers for

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  8.8
• Brand
  IMPRESA

Key specs2

Impeller Protection

Shields pump impellers and shaft seals by catching fine grit, pine needles, and pollen in the basket.

Basket Fit Range

Inground and above-ground baskets

Pros & cons43

Pros

• Protects pump impellers and mechanical shaft seals from grit and debris clogs
• Stretchy ultrafine nylon mesh adapts to inground and above-ground basket shapes
• Traps fine debris like pollen, pine needles, and scum before entering pipe lines
• Reusable design washes out with a standard garden hose when lightly soiled

Cons

• Pack of 10 provides fewer spares than larger 20-count bulk options
• Can starve the pump of water if left unchecked when heavy leaves fall
• Must be replaced every 4 to 8 weeks once the mesh stretches out or tears

9

(2-Pack) Above-Ground Skimmer Drain Cap Converts SFX1000 or SFX1500 Skimmer

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  6.8
• Brand
  TonGass

Key specs2

Cap Dimensions

7.2 in OD x 6.9 in ID x 1.2 in height

Included Conversion Hardware

• 2 skimmer drain caps
• 2 internal rubber seals
• 2 rolls of Teflon tape

Pros & cons53

Pros

• Converts SFX1000 and SFX1500 skimmer pump housings for sand filter connections
• Includes two internal rubber gaskets to ensure a tight leak-free connection
• Comes with two rolls of Teflon tape to seal screw threads during assembly
• Heavy-duty weatherproof plastic matches standard skimmer housing durability
• Ridged outer edges allow secure hand-tightening without slipping

Cons

• Engineered specifically for SFX1000 and SFX1500 housings and requires measuring for other models
• Outer diameter of 7.2 inches will not thread onto standard threaded pool wall returns
• Designed strictly for pump conversion rather than serving as a replacement cartridge

10

KimiBEE S1 Filters for Intex Spa, Type S1 Spa Filter

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  -
• Brand
  KimiBEE

Key specs2

Spa Cartridge Dimensions

4.25 in OD x 1.625 in ID x 2.875 in H

End Cap Material

Constructed with degradable PU material end caps that resist fracturing under spa water pressure.

Pros & cons53

Pros

• Sized specifically for Intex PureSpa hot tub units and 29001E filter chambers
• Glued center rod and PU end caps prevent pleat collapse and structural fractures
• Four-pack supplies at least two months of filtration on a two-week swap cycle
• Polyester fiber cloth captures hair, sediment, and fine sand effectively
• Rinses easily with fresh water to extend operational life between replacements

Cons

• Compact 2.875-inch height will not work in standard full-size pool filter housings
• Narrow 1.625-inch center hole is designed only for small spa pump core stems
• Manufacturer recommends replacing cartridges every two weeks for clean water

Last update on 2026-10-08 / Affiliate links / Images, Product Titles, and Product Highlights from Amazon Product Advertising API

FAQs

How do I know when to replace a pool filter cartridge instead of cleaning it?

Cleaning removes loose surface dirt, but fine oils and mineral scale eventually saturate the fabric weave over two to three seasons. If you thoroughly rinse your cartridge with a hose and the pressure gauge immediately returns to more than 5 pounds above your clean starting baseline, the material is clogged permanently. You should also replace the cartridge immediately if you discover ripped pleats, a cracked plastic center core, or brittle rubber end caps.

Why are air bubbles blowing out of my pool return jets after a filter change?

When you open the filter housing, the tank and adjacent pipes fill with ambient air. When you restart the pump, that volume of air gets pushed through the lines and exits into the pool through the return wall fittings. These bubbles should stop completely within two minutes once all air purges through the open relief valve. If bubbling continues indefinitely, check the clear pump strainer lid to make sure its rubber ring is not drawing in outside air on the suction side.

Do I really need to grease the rubber ring every time I open the filter?

Yes, applying a fresh film of silicone lubricant protects the rubber from friction tears and keeps the material supple. When you torque the heavy metal clamp band closed, the metal presses down with hundreds of pounds of mechanical force. Lubricant allows the rubber to slide smoothly into its molded groove without pinching or bunching, which prevents leaks and keeps the ring from sticking to the lid during future maintenance.

What should I do if the filter tank leaks water along the center seam after startup?

Immediately turn off the electrical breaker and open the air relief valve to vent all water pressure. Never attempt to tighten clamp bolts or tap the metal band while the housing holds pressure, because sudden shifts can cause the tank to fail. Once the gauge drops to zero, loosen the clamp, lift the dome, clean out any grit stuck under the rubber ring, realign the seal, and tighten the band evenly before trying again.