Cartridge Pool Filter Troubleshooting and Maintenance

Written by Michael Dean
May 22, 2024

cartridge pool filter troubleshooting

Any swimming pool owner would agree that when it comes to pools, the cleanliness of the water is a top-tier concern. Think about what goes into that water: bodily fluids, leaves, bacteria, the occasional stray animal, and more. Your cartridge filter works at maximum efficiency to ensure you aren’t swimming around in all that gunk. Read on if you’re troubleshooting for problems or just want general guidance on cartridge filter maintenance.

Main Takeaways

  • Common issues affecting cartridge pool filters are inconsistencies in pressure, leaky clamps, and poor water ratio.
  • Cartridge filters last around 5 years if cleaned often and maintained well.
  • The top three items to consider investing in for maximum cartridge efficiency: robotic pool cleaners, scum ducks, and a pool cover.

Common Cartridge Filter Problems

Cartridge filters are easy for the average homeowner to take care of, but they also do a good job keeping the water clean of debris and are designed to keep particulate levels down to 10-15 microns. However, they do sometimes act up.

Here are some of the common issues pool owners face regarding cartridge filters.

Pressure Inconsistency

Pool filters rely on a steady and consistent amount of pressure. If the pressure is too high, too low, too rapid, or too slow, operating could become hazardous. The average optimal range of the filter ranges from around 8 to 15 psi, although this can vary according to the model. Check the manufacturer’s instructions for your particular filter’s recommended psi levels.


Your cartridge is probably clogged with debris if the pressure is too high. If it’s too low, you might be experiencing a blockage caused by debris, air leaks, a broken valve, or maybe the filter is simply too small for your pool.


There are several reasons your pressure might be off. Regardless of the cause, it’s a good idea to learn how to read your pressure gauge and keep a close eye on it. However, a dirty cartridge is the most common reason for inconsistent water pressure. Inspect the cartridge frequently and pressure-wash it with clean water every few months. If pressure inconsistency persists, shut it off and have an expert look inside for more severe malfunctions.

I go over this solution and more in my guides on how to clean a cartridge filter and why your pool pressure is too high.

Leaky Clamp

The clamp in a cartridge pool filter is a thick metal band that goes around the main body of the filter. A typically used design for cartridge filters is a ‘clamshell’ where two halves are connected by a center clamp that holds the halves together. If it’s leaking water, it’s time to look closer at the seal.


A leaky clamp usually occurs due to high pressure or a poorly positioned clamp. The clamp can loosen over time due to vibrations or may simply crack due to a lack of lubrication. Luckily, it’s easy to sort out most of these issues if you have the right equipment!


A leaky clamp may sound intimidating, but it is fixable if you go through the following steps:

  1. Switch off the pump, drain the filter tank, and remove the clamp’s band from the body, separating the two halves.
  2. Look for the o-ring. It’s a gasket of flexible material that creates the seal. Remove it, rinse it with water, and use a cloth to wipe it clean of any accumulated muck and the rim of the tank where it rests.
  3. Inspect the ring for any wear and tear – if it’s cracked, has dry rot, or is no longer completely round, get a new o-ring.
  4. If it looks alright, lubricate the o-ring with silicone pool lube and reinstall it, securing the clamp band properly around the two halves and tightening the bolt until you can see the springs are touching.
  5. Turn the pump back on and check for leaks.

Unbalanced Chemical Levels

Your pool’s chemical balance always matters. It is really important to maintain the perfect ratio between the filtering, pH levels, acidic and alkaline levels, and chlorine. A dirty, murky pool with a poor chemical ratio makes a cartridge filter’s job ten times harder.


An unbalanced water ratio can be caused by either too much or not enough chlorine, the passage of time, too much heat or sunlight, the quality of your tap water, or algae buildups.


Check the water’s pH, alkaline, and chlorine levels often. 7.4 is a perfect pH level; alkaline levels should hover between 80-150 ppm, and chlorine levels should hover between 1-3 ppm (depending on the size of the pool). Read my pool chemistry basics and how to test your pool water guides for instructions on how to do everything.

When is it Time to Replace Your Cartridge Filter?

Replacing your cartridge filter is necessary for pool filtration upkeep, but it isn’t always easy to know when. The pressure gauge is a major element that can help you gauge when it’s time for a replacement.

Your pressure gauge can alert you to a clogged cartridge that needs cleaning or replacement. If the gauge climbs up by around 8 psi or more, the cartridge needs to be taken out and examined. If you clean it thoroughly and reinsert it, but the pressure climbs up again relatively quickly, it’s a good time to replace the cartridge.

Another way to check if it’s time for a replacement is simply using your eyes. Remove the cartridge from the tank and examine the bands, the pleats, and the end caps. If the bands are worn out or frayed, the pleats are deformed, or the end caps are cracked or broken, the cartridge needs to be swapped out with a new one.

Cartridge filters generally have a long lifespan, but check what your manufacturer’s guidelines say regarding a replacement. For example, Unicel recommends replacing a cartridge every 15 cleanings or so. If you clean your filter three times a year every four months, you’re looking at a lifespan of roughly five years or less.

I have an entire article on the signs you need to replace your pool filter cartridge, so check that for more tips.

When Is It Time To Replace Your Entire Filter System?

There will also come a time when you need to replace the entire pool filter pump system. Such equipment has a life expectancy of 8-12 years, provided it has been well-serviced.

Some signs that you need to replace the entire pump are:

  • The filter spits out an alarming amount of bubbles due to several cracks and air leaks in the equipment.
  • The filter makes grinding, screeching, rumbling sounds or quick, repetitive pops. Pool filter systems should be quiet.
  • The water is constantly cloudy or green, and you have a tough time maintaining a good pH balance even though the cartridge is new and the pressure gauge is reporting a healthy and consistent amount of pressure.

As a top tip, before opting for a complete replacement, call a pool expert to see if these problems are repairable.

Cartridge Pool Filter Maintenance Tips

If you’re keen on making sure a cartridge and the entire filter system last as long as possible, here are some points to follow to maintain a crystal-clear pool:

  • Clean often – not just the pump or the cartridges but the pool itself. Skim it with a net every few days. Also, consider investing in a robotic pool cleaner that’ll thoroughly clean out any settled debris from the pool floor.
  • Use a scum duck – it’s an oil-absorbing sponge and can be placed in your pool to soak up all the oils left behind by swimmers. This means less oily gunk goes into the filter, which is good for the swimming pool and overall equipment.
  • Deep clean your cartridge – soak the cartridge in a proper cartridge cleaning solution overnight to dissolve all the oils, grime, and dirt.
  • Get a pool cover – it’s a simple solution that goes miles in preventing all sorts of debris from dropping into the pool. The less preventable work a cartridge filter has to do, the longer it lasts.

Get My Free Pool Care Checklist

Download my free, printable pool maintenance checklist to help you accomplish regular pool care tasks for any type of swimming pool.

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Cartridge Filters Are Easy to Maintain

Cartridge filters are easy to maintain and replace, so putting in the time and effort goes a long way in seeing a beautiful, sparkling swimming pool with clear blue water. If you still need help finding a replacement cartridge or figuring out a problem, or if you have any questions about how to care for an aging filter system, get in touch! You can also read my guide on pool filter troubleshooting. If you need a new filter, you can check out my recommendations in my guide on the best pool filters.

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