Pool Filters


Example of a Cartridge Filter CARTRIDGE POOL FILTERS


Filter of choice for most spas, and many smaller above ground pools, the cartridge filter is enjoying a resurgence in popularity. The cartridge filter element, an aquatic version of the pleated air filter in your car, traps dirt and particles of 25 - 100 microns in size. The cartridge is removed from the tank and hosed thoroughly, top to bottom, with a high pressure hose to remove dirt when the pressure gauge rises 8 - 10 lbs. above its clean reading. I know some people that take their cartridges to the local self serve car wash place for cleaning, but too much pressure may damage the cartridge. Each time the cartridge filter element is cleaned, some of its filtering ability is reduced.

Today's filter cartridges are made from spun polyester, and the brand Reemay is the brand of choice. Reemay is pleated and wrapped around a heavy plastic or pvc core that allows water to flow from the outside of the cartridge to the center core. Pool filter cartridges are bound on each end with a heavy type of rubbery plastic that is melted or fused to the ends of the rolled up pleats and the inner core.

Unicel is a popular manufacturer of replacement cartridges for most of the pool equipment manufacturers. Other brands have gained some marketshare in recent years, notably Filbur and Pleatco. Pleatco has a unique core design, but they mostly use the same materials and methods in manufacture. OEM cartridges are also available, but be prepared to pay a premium for the brand name!

The cartridge should be replaced every 3 - 5 yrs, depending on the work it was asked to do. If the filter was a bit undersized, and had some algae every year and lots of tree debris, etc. then it may last only 1 - 2 years. Nicely sized cartridge filters can operate for 6 months between cleanings and get more than 5 yrs from the cartridges.


"How do I Backwash my Cartridge Filter?


A trick question. There is no backwash valve on a cartridge filter because today's pool filter cartridges aren't built for backwards flow. Instead, the pump is shut off, air bleeder opened to drain the tank, lid removed, cartridge(s) removed, hosed thoroughly top to bottom, and replaced. It's a bit of a pain to do, but hopefully the filter is sized so that it's a once or twice per year job.  Another advantage is that cartridge cleaning doesn't waste as much water as backwashing.


Soaking the cartridge in a TSP (trisodium-phosphate) or similar solution prior to hosing will improve your cleaning. Do not use TSP if you utilize Baquacil or Soft Swim for sanitation.


Use of a clarifier or Chitin product like Sea-Klear is a great help to a cartridge filter. Some people also increase the filter efficacy by adding a small amount of synthetic filter aid powder (1 - 2 cups) through skimmer. D.E. powder is not recommended by most manufacturers, as it can clog the pores of the cartridge.

Poor water Quality?

If you have debris bypassing the filter cartridge, then dirt and particulate matter is probably also getting by the filter. Cartridge filters are designed to force the water through the pleats, and as we know, water will always take the path of least resistance. Make sure that all internal parts are in place, if any, and that the cartridge is properly seated in place when reinstalling.

Poor sanitation, poor water balance, and pool circulation could be another cause, and it could have nothing to do with the filtering at all. It could also indicate a need to replace the cartridge, and as a filter ages, the length of time between necessary cleanings becomes shorter. Some filters are sized fine for good water conditions, and they do well when water conditions are good, but try to clean up an algae bloom or cloudy water and they struggle. If this is you, look at the size of your filter, it may be undersized. Bigger is better with pool filters (but not with pool pumps)!


How long should I run my Cartridge pool filter each day?


It Depends. Careful experimentation will show you when the water quality begins to suffer. Many people with smaller, older equipment (filter/ pump) run their systems 24 hours per day. The average (I would guess) would be about 16 hours. BUT! It depends on your system. Undersized? Old? High pool Use? Large Debris Load? Heavy Sunlight? Any of these factors call for extra filtering, and extra chemicals. If you're too frugal with the electricity, or if you forget to turn the pump back on - you likely pay more in chemical costs.

Leaking Cartridge filter?

Most Cartridge. filters have a belly band clamp with a large O-ring between tank halves. The clamp band may be a spin off, no tools required type. The o-ring between the tank and the lid can become distended or flattened and may need to be replaced if water is dripping from the center clamp. Clean and Lubricate the o-ring annually, and always make sure to re-secure the lid properly after removing. Caution: Do Not remove the center clamp while the pump is running, and without first releasing pressure inside the tank.

Most cartridge filters have a drain, some smaller ones do not. You may experience leaking around the drain assembly, cap or plug. Teflon tape on the threads usually helps, and can also be used around the air bleeder / pressure guage assembly to keep it from leaking.

Filter Cartridge Replacement:

Right off the shelf for $40 - $100, depending on its size. No professional labor needed.


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