Proper circulation and filtration are key to clean and sparkling swimming pool water. A cartridge filter when clean only filters 10-20 microns, so between the different types of filters, it leaves the largest amount of debris to begin with. Consider a human hair is about 50 microns. So it is uber important to make sure we are cleaning our cartridge filter as often as needed. Otherwise your pool will start to look cloudy.
When to Clean
A good rule of thumb is approximately every 6 months, although you may get a little more or less time in between, depending on usage and amount of debris. When you clean your filter you will start with what is known as your personal “clean starting pressure”. This varies from pool to pool based on your total dynamic head and design flow rate. When your filter reads 8-10 pounds per square inch (PSI) above YOUR clean starting pressure, it is time to clean it. For example, if your clean starting pressure is at 14psi, once the filter gauge reads 22-24 PSI, it is time to clean it. A filter clean is also needed after a phosphate treatment. Just killed off some algae? You guessed it. Time to clean the filter. When treating algae, sometimes we have to clean the filter twice: once before to enable enough room to capture the algae and once after to get rid of the algae accumulated in the filter.
How to Clean
The first rule when working on any of your pool equipment is to make sure the system is off. Next, you’ll need to bleed out the air that resides in the tank. This is done by turning the air relief valve to the open position. Make sure it isn’t pointing towards you! Also, don’t open the filter while it is under pressure. Not only could this cause damage, but could injure you.
The next step is to remove the clamp that sits around the middle of the filter that secures the lid on. Remove the rubber o-ring that is seated in the bottom portion of the filter after removing the lid. Examine the o-ring. Is flat? Swollen? Stretched out? Old? It may be a good idea to replace it. Especially if it has been a few years. You can find one at a local pool store for $20-$30, depending on your filter. Some older filters have a metal clamp with screws. You’ll want to Google how to remove this or even hire someone to do it because these can be a pain.
Go ahead and take the cartridge or cartridges out. Once again, we are going to examine them. If more than one plastic band is broken, the pleats are spaced out all funky or it stays oily and dirty looking after a clean…it may be time to replace. If you were getting debris returning to the pool prior to beginning the clean, this can be a good indicator that you may need new cartridges. A decent quality filter typically lasts 3-5 years, but this depends on how dirty you let it get and the water chemistry. So don’t hold me to that number. Any obvious rips or tears are indicative of needing to replace the cartridges as well.
You’ll want to get off the large debris stuck to the filter. You can use your regular garden hose to do this. I like to start at the top of the cartridge and work my way down, then flip it around and do it again. If your hose spray isn’t strong enough, they do make special nozzles. There are even some “cartridge cleaning “ attachments available. Still have debris stuck? A delicate brush can be used, but keep in mind this can wear down the material of the cartridge.
So, we have gotten the debris off, but what about other contaminants like algae, oils, and other organic and inorganic materials?
To Soak or to Spray Clean?
There are two different types of filter cleaner available. One is a spray and rinse. And one is to soak in a bucket and rinse. It really depends on just how dirty your cartridges are. Talk with a pool professional if you are unsure which one to use. The best product would be a combo degreaser and cleaner.
If using a spray cleaner, make sure to get the entire cartridge’s surface area AND between the pleats. If soaking, always follow the product’s instructions. Some may be for a couple of hours, while others require overnight soaking. However, you apply the solvent, the next step will be to thoroughly rinse off the cartridges
If your cartridges have a lot of calcium build up. You can use a 4 to 1 muriatic acid mixture to soak your cartridges in. Calcium build up can make the cartridges heavier and thus less efficient. Consult a professional before attempting this process.
Now we need to reassemble the filter tank. Place your clean cartridges back into the canister. Put on any attachments, such as a manifold, if your filter has one. Lube up the tank o-ring with a silicone based pool lube to get a nice, tight seal. We don’t want water dripping out because we know that water dripping when the system is on equals air getting in when the system is off. Replace the clamp tightly around the canister. You may even want to gently use a rubber mallet to bang out any slack, allowing you to get the clamp as snug as possible. Don’t forget to turn the air release valve back to closed! Turn on your system and see if everything is copesthetic. Now turn your dial to set the “clean” arrow to the starting pressure. If your gauge does not have this feature, a sharpie of a piece of tape can be used to mark it.
Congrats! You have just performed a crucial necessity to have a clean pool! If you are still uncomfortable with the process, I always suggest watching YouTube videos. Another great investment would be to hire a professional to do it the first time and watch them. Then you will know how to do it moving forward. See you poolside!