How to Clean a Pool Cartridge Filter

Knowing how to clean a pool cartridge filter is one of the most important factors in maintaining the health and safety of your swimming pool and spa.

Cartridge filtration systems are popular for all types of swimming pools, hot tubs and spas. They are less expensive than sand filters and easier to operate but you cannot backwash a cartridge filter. Cartridge filters pass water through a cylindrical fan-folded cartridge element to trap dirt and contaminants. Periodically remove the cartridge from the filter tank and clean with a garden hose. Frequently cleaning the cartridge filter element will keep your pool water clean, clear and safe for swimming. Eventually, after 3 or 4 years use, the filter cartridge becomes worn out or damaged and must be replaced.

Clean the Pool Skimmer Basket

Don’t forget to regularly clean the skimmer basket. The skimmer box is the first line of defense to remove larger items of debris from your pool. It reduces the need tp clean your pool cartridge filter as often.

When leaves, insects, or any other larger pieces of debris enter the pool they float on the surface for a while before sinking to the bottom. The pool pump provides suction to the skimmer box. Its purpose is to remove all floating debris from the surface of the pool and trap it in the basket. The skimmer box stops larger items of dirt and debris being pumped into the filter.

When the skimmer box is dirty water flow to the filter is restricted. This puts a strain on the pump motor which must work harder to move the water through the filtration system. And if water the filtration system cannot turnover all the water in the pool each day the pool will remain dirty.

I recommend the use of skimmer basket filter socks to collect small debris and save your filter cartridge from cleaning.

Skimmer Basket Cleaning Procedure

1. Turn off the filtration system
2. Remove the lid from the skimmer box
3. Remove the skimmer basket from the box
4. Empty the basket into the garbage bin (not your garden as it will blow back into the pool)
5. Replace the basket in the skimmer box
6. Replace the skimmer box lid
7. Turn on the filtration system to the automatic setting
8. Check the pressure reading on the filter gauge is normal

Read our article on How to Clean a Swimming Pool

How to Clean a Cartridge Pool Filter

Cartridge filters do not require a cleaning media such as sand or D.E. powder to trap dirt and debris. They clean the water with a cartridge element which is easily removed to clean or replace.

Note: The filter cartridge must be removed for cleaning. There is no way to backwash a cartridge filter element. When a filtration system is installed with a cartridge filter the plumbing does not allow for backwashing to the drain.

I recommend using at least two filter cartridges. When your cartridge filter needs cleaning swap out the cartridge element with the clean one so your filtration system can operate immediately. Clean the dirty cartridge, allow to dry and store in out of the weather.

When to Clean the Cartridge Filter

All cartridge filters have a pressure gauge indicating the water pressure inside the tank when the pump is operating. When the filter cartridge is clean or new remember the pressure reading on the pressure gauge. This is the filter’s normal operating pressure. It’s important to learn that figure so you can check the gauge and know when the filter requires cleaning.

Clean the filter cartridge element once the pressure gauge has reached 50kPa above the normal operating pressure. For example, a filter that normally operates at 50kPa needs to be cleaned at 100kPa. This figure may be different for your type of filter.

During the summer season and when the pool is heavily in use the cartridge element will require to be cleaned frequently, for example, every week. In the winter when the pool is not used and it is covered the element will only require infrequent cleaning.

If cleaning the element does not reduce the pressure back to the filter’s normal operating pressure the cartridge must be replaced.

Note: Always refer to the manufacturer’s instructions for your type of filter.

Cartridge Filter Cleaning Procedure

1. Switch off the filtration system at the power point to ensure the motor doesn’t activate automatically.
2. Loosen the air bleed screw on top of the filter lid & release the air pressure. The water in the tank will drain away once the air pressure is released. Leave the air bleed screw partially loose.
3. Remove the filter’s lid lock (usually it’s a lid lock ring that unscrews). I find you need a rubber mallet to gently tap the locking ring to loosen it. Then unscrew it with your hands.
4. Remove the lid from the filter tank. The lid fitting is very tight and may have to be carefully levered upwards around the edges to open the lid.
5. Remove the cartridge element from the filter tank.

Wash the Filter

1. Wash the filter element on grass or where the water will flow into a drain as the water will be dirty.
2. Use a garden hose with a spray nozzle to clean the dirty element. Do not use a pressure washer as it will damage the element. Stand the element upright and begin hosing from the top to the bottom of the element ensuring you clean between all the pleats. Keep cleaning the element until the water runs clear. When the element is old and difficult to clean replace it.
3. Elements can be soaked overnight in a cartridge cleaning solution. This will remove or loosen all dirt not removed by hosing the element. This is usually only required on very dirty or old elements.

Refit the Filter

1. After cleaning, place the cartridge element back in the filter tank ensuring it is seated correctly on the bottom of the tank.
2. Place the lid back on to the tank. Ensure the lid’s O-ring seal is in place. Place the lid the correct way round so you can read the pressure gauge. Applying a light amount of lubricant to the lid O-ring seal will help preserve it and make it easier to remove the lid again.
3. Replace the tank’s lid lock (usually it’s a lid lock ring that screws around the lid). Screw the lid lock ring into place using hand pressure only. Do not overtighten the lid lock ring.

Cartridge Filter Start Up Procedure

1. Ensure the air bleed screw on top of the filter lid is partially open to allow air to expel from the tank. Do not remove the air bleed screw as water will shoot out of the opening when the pump is activated. Do not stand over the lid and switch on the pump as the air bleed screw may come loose and be shot upwards towards you.
2. Switch on the filtration system and pool pump motor.
3. Allow the pump to operate until all the air has been expelled from the filter tank and the tank is full of water. You will know when all the air is expelled because water will come out of the air bleed screw.
4. Tighten the air bleed screw until water no longer runs from the air bleed. Only tighten the screw with your hands to a finger tightness. Do not tighten with a wrench or any other tools as you may damage the screw.
5. Check the pressure gauge to ensure it’s in the normal operating range.
6. The filter is ready for operation.

When to Replace the Cartridge Filter Element

1. You are cleaning your filter cartridge and you notice it has become more difficult to clean or won’t clean easily it’s time for a new cartridge.
2. When your filter element has any damage to the pleats or holes in the filter replace it.
3. If the filter is returning dirt back to the pool there will be a hole in the filter.
4. If after cleaning the filter element the pressure on the filter pressure gauge does not return to the filter’s normal operating pressure the cartridge must be replaced.
5. There is low water flow through the filter and the return outlet jets have a weak flow.
6. Pool filter cartridges can last from 2 to 5 years depending on how you clean your pool and filter. The cartridges clog up inside the element over time and cannot be cleaned properly. When your element is older than 3 years replace it.

How to Make a Cartridge Filter Last Longer

Vacuum the pool to waste

The simplest way to prolong the life span of a filter element is to manually vacuum the swimming pool to waste (or drain) rather than through the filter. Vacuum the pool whenever there is dirt on the bottom or weekly.

When you vacuum the bottom of the pool there is no need to filter the water as it will be very dirty. Switch the filter valve to waste (the drain) while vacuuming and the dirty water will be pumped into the drain. This increases the life of the filter element and reduces the requirement to clean the filter element.

Note: Vacuuming to waste removes some water from your pool so you will need to top up with the hose for a few minutes. The water chemistry will not change as the volume of water lost to the drain is very small. This process also helps to reduce the build-up of total dissolved solids (TDS) in pool water.

Install a skimmer basket filter bag

The use of a skimmer basket filter bag helps to extend the life span of your filter cartridge. Simply place the filter bag into the skimmer basket to capture more dirt and debris than the skimmer basket alone. Throw the full filter bag in the garbage bin and replace with a new filter bag. This prevents the filter from becoming clogged with dirt and reduces the frequency of filter cleaning.

Use an automatic cleaner

Most automatic cleaners store the dirt and debris in their own bag or canister. You empty the canister into a garbage bin. This reduces the amount of dirt and debris from passing through the filtration system and reduces the frequency of filter cleaning. You may be able to reduce the pump hours saving electricity.

Clean the cartridge element more frequently

When you let a filter element become very dirty it will become more difficult to clean and the element may become damaged requiring replacement. When you clean the element more frequently it will be less dirty and easier to clean every time. The swimming pool water will also be cleaner, clearer and require less chemicals.

Use two filter elements

I recommend using two filter elements so you can easily and quickly swap out the dirty element and install a clean one. You can clean the dirty element by soaking it in water with a mild detergent. Then hose it down afterwards. Store it in a cool and dry place.

How to Clean the Filter Plumbing Pipes

Filtration system plumbing pipes become blocked for a number of reasons. When bags of salt are added to the pool the undissolved salt can be sucked in the plumbing pipes and filter. Leaves and larger items of debris are sucked into the plumbing. Granular pool chemicals (like stabilizer) are placed in the skimmer box and pumped into the filter. And there may be a build-up of calcium scale in the pipes which is common in areas affected by hard water supplies.

The quickest and easiest way to clean the plumbing pipes to and from the pool from the filter is to run the pool pump without the filter cartridge. The pump will run the maximum water flow rate through the plumbing to clean out the pipes as there is no resistance from the filter cartridge.

Use this method to circulate the water around the pool without filtering when you have added salt or chemicals to the pool and just want to mix up the pool water to dissolve the salt or chemicals.

Conclusion

Cartridge filtration systems are great for all types of pools including inground pools and spas because they are easy to clean and maintain. However, they do require frequent cleaning. I recommend using two cartridge elements, a skimmer basket filter bag and vacuuming the pool to waste to reduce the need to clean the cartridge filter. A pool cover is a good investment because it reduces the amount of dirt and debris entering the pool. This keeps your pool cleaner longer and saves you from frequently cleaning the filtration system’s filter element.