Pool Filters – Improving your Pool Filtration

drpool-cartridgeAs we head into another pool season, I have to ask – “How’s your filter doing?”

Hello again, Dr. Pool here. Today’s discussion centers not on pool chemicals, but on the closely related topic of pool filtration and circulation.

Filtration and sanitation are closely linked, working together to produce clean pool water. A proper balance between the two is essential. If filtration is lacking, sanitation (and circulation) must be increased to compensate.

My esteemed colleague Jackie promised in her most recent post, and I quote – “…better water quality and reduced chemical use with a larger filter”.

giant pool filterIncreasing the size of the pool filter is certainly one way to improve your filtration; an oversized filter can help prevent many water problems before they occur.

However, this post is not attempting to steer you to a new pool filter, rather our goal is to instruct on ways to improve the filtration on your existing filter, without expensive pool filter replacement.


A cartridge pool filter has the simplest of design, water is pumped into the filter tank and forced to pass through pleats of spun polyester. The dirt is trapped in the many layers of woven fiber, and cleaned manually by removing the cartridges and spraying with a garden hose.

Improving Cartridge Filter Efficacy

Don’t Over-Clean: Filter cartridges become a bit more effective at trapping dirt when the cartridges are slightly dirty. Trapped dirt helps trap more dirt. Secondly, each time a pool filter cartridge is cleaned, the fibers loosen and dirt trapping ability is reduced slightly. Clean your cartridges when the pressure gauge is 8-10 lbs over the clean, starting pressure, or when flow rate is significantly reduced.

filter-flosser-Clean Gently: Although a good volume of water is important, too much water pressure can damage the fibers. Never use a pressure washer to clean filter cartridges. The Filter Flosser can be used to focus the water stream, very useful for low flow garden hoses.

filter-clean product from intheswimRemove Oils & Minerals: These can both clog the tiny spaces between the filter fabric fibers. If the pressure gauge is not dropping as far as it used to after cleaning the cartridge, clean it with our Filter Cleaner, which breaks down calcium deposits and removes oils from swimmers and airborne pollutants.

Use a Larger Cartridge: Not larger in size, but in square feet of filter area. By adding more pleats, or folds in the cartridge, the filter surface area is increased. When buying a new filter cartridge, our Filter Finder utility will present you with several options for your filter. For instance, the Hayward cartridge CX500 is a 50 sq. ft. filter measuring 7″x20″. The same size filter is also available in 3 other versions with 55, 75 and 81 sq. ft. of surface area.

microban-cartridgeUse a Microban Cartridge: In their distinctive blue color, Microban® filter cartridges have built in microbial protection against bacteria, mold and algae. When you search for your filter cartridge using our Filter Finder, if a Microban cartridge is made in your size, it will display, with a part number that ends in -M. Microban technology will not keep your pool sanitary, but it can prevent algae and bacteria from living deep within the fabric fibers.


A sand filter uses specially graded sand to trap dirt and bacteria as water is pumped through the sand bed. Backwashing, or reversing the flow through the filter, flushes the sand bed clean. Simple to use, low maintenance pool filter.

Improving Sand Filter Efficacy

Don’t Over-Backwash: Even more so than cartridge filters, having a low-level of dirt build-up between the grains of sands helps to trap more dirt. Backwashing as a regular maintenance task, instead of waiting until the pressure gauge is 8-10 lbs higher, can reduce overall filtration efficiency.

pool-filter-sand-Replace your Filter Sand: If you have a very small sand filter, you may need to change the filter sand every season. For appropriately sized sand filters, 5-7 years is about how long it takes to round-off the sharp edges of the sand grains, resulting in reduced dirt-trapping ability.

Switch to Sand Alternative: Pool filter sand is specially graded, .45-.55 mm in size, known as #20 silica sand. Technology has brought us ZeoSand, made from natural zeolite particles, which not only filters better, but traps ammonia and chloramines. FilterGlass is another alternative, made from recycled glass, and is the best filtration media you can use, filtering down to under 2 microns!pool-filter-sand-types

Remove Oils & Minerals: Just like other filter types, body oils or oil from trees or pollutants can cause filter problems, such as coagulated clumps inside the filter tank. Hard water areas can cause calcification of the sand bed, turning filter sand into a type of sand stone material. Filter Cleaner breaks down calcium deposits and removes oils from sand filters. Use annually on sand filters to improve flow rates and filtration. If you have continuous problems with oils and minerals in your pool, control them with enzymes and sequestrants.

clarifiersUse Clarifier: Clarifiers are in a group of chemicals called coagulants. They are attracted to any suspended particles in the pool, and their benefit is that they clump together dozens of very tiny particles into a larger, more easily filtered size. Small amounts of aluminum sulfate added to the skimmer, can be used as a filter aid for sand filters, as it forms a gelatinous layer on top of the sand bed.


Most DE filters don’t require assistance to keep a pool clear, but if they are on the small side, or when trying to clear very turbid and “thick” pool water, they can have trouble. There are some things you can do to improve the cleaning ability of a DE pool filter.

Improving DE Filter Efficacy

Caked-on-de-powderDon’t Overdose with DE: When you initially start up a very clean DE filter, add the recommended ‘charge’ of DE powder, which is usually a 1 lb coffee can size scoop of DE powder for every 5 sq. ft. of filter surface area. After backwashing, cut the amount by 1/3-1/2.

Backwashing only removes 50-70% of the DE powder in the tank, the remainder is trapped between the grids. Adding a full charge after every backwash will quickly build-up to reduce water flow and filter effectiveness.

hayward-bump-handleBump the Filter: The Hayward Perflex DE filter has a ‘bump handle’ on top that is used to knock off the cake of DE powder that coats the fingers (grids), Most other types of DE filters don’t have a bump handle, but you can replicate the action.

Bumping refers to a quick backwash, of just 10-15 seconds. Then move the valve to the Filter position and run the pump for another 10-15 seconds. Repeat this action 2-3 times to knock off and mix-up the DE cake. This results in faster flow rates, and lower pressure on the filter gauge.

Slurry Coat: In the old days, pool owners with a DE filter could use a slurry feeder, which added small amounts of DE powder into the filter continuously. These have fallen out of fashion, but some pool owners combine bumping with slurry feeding. After bumping the filter, add 1/4 cup of DE powder to the filter. If done weekly, you may go months before needing a full backwash.

de-filter-grids at IntheswimRemove & Clean: The grids or fingers of a DE filter need to be removed and cleaned every season. A thorough cleaning with a garden hose will remove excess DE cake that has bridged between DE grids, and help remove accumulated wastes, oils and minerals. Like the other pool filter types above, Filter Cleaner can be used to improve DE filtration. Especially useful for stained or oily DE grids, or in areas with high levels of minerals or metals.

Grid Maintenance: As you give your DE grid assembly an annual cleaning, inspect it closely for any tears in the grid fabric. Grids can be replaced individually as needed. There are 7 large grids and 1 small grid in a typical vertical grid assembly as shown above. Also inspect for cracks in the manifold on top, or problems with the air bleeder assembly, which can be a fabric “sock”, or a small metal screen. Ensure that your entire grid assembly is held together tightly by the through bolts and that the standpipe o-ring is intact.

aqua-perlUse DE substitute: DE powder is an excellent filtration medium, but technology has improved upon even the diatom. Aqua-Perl is a volcanic paper pulp that has superior dirt-trapping ability and lower density as compared to DE powder. The best thing is that you only use half as much Aqua-Perl, which reduces bridging between grids, and results in more complete backwashes.

If your pool filter is limping along, try some of these tips above to improve your filter performance, and enjoy clearer pool water this summer!

Class dismissed!


Dr. Pool



Pool Filters – Improving your Pool Filtration — 3 Comments

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