How to Improve your Pool Filtration

For those of you who have a pool filter that is somewhat… marginal, this post is for you.

Many pool filters out there are too small, too inefficient or just plain worn out. Others work fine most of the year, but have trouble during spring clean-up.

Here’s some tips to eek out a little more filtration ability from your overworked and underpaid pool filter.

Cartridge Pool Filters

A cartridge pool filter has one or more pleated cartridges that are similar to the air filter on your car. The water is forced into the pleats, where it leaves behind the dirt, trapped within the folds. As the pressure rises on the filter tank gauge, the flow rate decreases and eventually, the cartridge is removed, hosed clean – and the cycle begins anew.

Tips to improve pool cartridge filtration

If dirt and debris seems to bypass your filter cartridge, it probably is. Look for cracks in the ends of your cartridge, or rips in the pleats. Another cause of dirt getting around the cartridge (and not through it) – are misplaced or misaligned parts within the filter. Look to your filter’s owner’s manual to identify location and placement of internal manifolds. Check these internal parts for cracks or missing o-rings. Sometimes it’s a matter of properly “seating” the cartridge into the base of the filter tank, before putting the lid back on.

In areas that have hard water, mineral deposits can clog the tiny pores of a filter cartridge. In this case, your pressure gauge will likely be reading higher than before, as the water tries to push through the clogged cartridge. To remedy this situation, soak your filter cartridge in a 10:1 solution of water to acid to dissolve the minerals.

Cartridges can also become clogged with oily substances – from suntan oil, cosmetics, hair care products and just plain old body oils. Soaking your cartridges in a solution of TSP will break down the oils. If oils are a problem in your pool, use a pool enzyme product such as Pool Perfect to break down the oils. Amazing stuff!granular filter cleaner

The best treatment for overworked filter cartridges is to regularly use a granular Filter Clean product. If you’re not sure if your filter cartridge is clogged with minerals or with oils – Filter Clean takes care of them both! Just soak the cartridges overnight, then rinse thoroughly.

Adding a Clarifier to your pool water can help pool filters immensely. Pool Clarifiers act as coagulants, clumping together very tiny particles into larger, filterable clumps. Be careful not to overdose however, using too much Clarifier, can cause the opposite effect!

Adding a small amount of DE powder substitute (a coffee cup size amount) to your skimmer can help your pool filter cartridge to trap more dirt. Don’t overdose with the powder either, too much of it can clog the cartridge or even cause very small rips to the fabric. Aqua-Perl is a DE alternative that I have used with success.

If you want to increase the filtering ability of your cartridge filter, maybe it’s time to replace the cartridge? Each time your cartridge is cleaned, it loses a little bit of it’s filtering ability. After 20 or so cleanings, or 2-3 years, it’s time to buy another.

Is your cartridge filter too small? Not uncommon to have an undersized filter. As a general rule, buy a filter with 100 sq ft of filter surface area for every 10000 gallons of pool water. And you can’t go too big – the larger the cartridge pool filter, the better the filtration, and the longer the filter cycle (length of time between cleanings).

Sand Pool Filters

Sand pool filters are the simplest to operate and the easiest to maintain. Even those intimidated by their pool equipment can manage to backwash the sand filter. Sand filters have a simple design. Water is pumped into the top of the tank, then pushed through the sand bed and into slotted pipes in the bottom of the tank. The dirt is left behind, trapped in the sand bed, until you reverse the flow, and backwash the dirt out of the filter tank.

Sand filters are not perfect however, they can have problems with allowing fine debris to pass through. Here’s some of the common problems we have seen with sand pool filters.

Mud-Balling: Sounds like the sport we used to play outside of our college dorm, but for sand filters, this refers to oily balls of sand, lint and who knows what else, that can be found in the top few inches of pool sand. Oils that have been removed from the pool water coagulate to form these mud-balls. Remove manually and replace with fresh pool filter sand (#20 silica, 45-55mm), or use our granular Filter Clean product mentioned above. Pool Perfect pool enzymes

If oils are a problem in your pool, using an enzyme product like Pool Perfect will remedy the situation. These are the same types of enzymes that are used in ocean oil spills, so you know it’s heavy duty stuff.

Channeling: Not otherworldly spirits, but well-worn paths that the water takes through the sand bed. If you notice that dirt and debris is passing right through your filter, you may have channeling caused by a much too powerful pool pump.The remedy for this is a smaller pump, or a larger filter, or installing a bypass valve to divert extra water which is beyond the sand filter’s design flow rate.

Calcification: In areas that have very hard water, with high calcium hardness levels, you may find that the filter sand has turned to stone! Well, not quite that hard, but very high hardness levels can cause your once free-flowing sand bed to clump-up into hard, calcified chunks. Solution? Change the filter sand, and make regular use of a granular filter cleaning product to keep it from reoccurring.

Seeing very fine, silty dirt pass back into the pool while vacuuming is somewhat normal, I hate to say. It is trapping most of the dirt, but some of it is getting pushed all the way through. To fix this, you could vacuum to waste, if you have a multiport valve. You can also add a pound of Aluminum Sulfate to the filter, via the skimmer. Alum, as it’s called, will form a gelatinous layer on top of the sand bed and dramatically improve filtration.

Filter sand will last 5-10 years, depending on the size of the filter. Larger filter tank sizes seem to keep the sand fresher longer, but very small filters may need annual sand changes – for those that are quite undersized. When sand particles become worn, they lose the sharp edges that keeps them laying together in layers. Eventually, they become rounded, and the filtration ability reduces.

If your sand filter seems to be working fine, and you have no water quality issues, then the sand is probably fine. If you start to have cloudiness issues, or algae issues, or you are backwashing more frequently – it may be time to change the filter sand.

There are now more options for sand filter media. You can Zeo Sand replaces regular filter sanduse regular pool filter sand, or we have alternative products Рone called Zeo-Sand and another called Filter Glass. The natural crystalline structures are many times more effective than regular filter sand, filtering down to a ridiculously small particle size, and even removing cellular matter, ammonia and chloramines!

Diatomaceous Earth Pool Filters

D.E. pool filters are known to be superior to the other two types of pool filters in terms of their particle size filtering ability. They have the downside of being the most expensive type of filter to buy, and they are a bit more work to maintain – but boy, do they work well!

If your DE filter is not working so well, if it’s clogging up quickly, requiring frequent backwashing, here’s some troubleshooting tips.

  1. Remove the grid assembly from the tank and hose thoroughly.
  2. Soak the grids in a Filter Grid Cleaning solution like Filter Clean.
  3. Inspect the grid assembly, then replace the grids into the tank.
  4. Add a Full Charge* of DE powder through the skimmer

*1lb coffee can size scoop per 5 sq ft filter surface area, DE substitutes require less. Requires less than a Full Charge after backwashing, because you only backwash out about 70%.

If your DE filter is blowing back DE into the pool, this could be caused by several things. It’s not dangerous, first of all – and you will continue to filter the water, just a little less effectively. Here’s the common causes of DE powder blow-back.

  1. Remove DE grids to inspect for tears or rips in the fabric.
  2. Inspect the top manifold for cracks or a missing air bleeder.
  3. Check your multiport or push-pull valve, which could allow blow-back.
  4. Check the o-ring on top of the standpipe, inside the tank. Missing?

Well, that’s all I got for now – thanks for reading about how to improve the filtering ability of your pool filter. If you are having trouble clearing the pool water, don’t assume that the water chemistry is wrong, look to the filter – it could be the source of your water clarity problem!

Enjoy your Pool!


Brett Rotelli
InTheSwim Staff Blogger




How to Improve your Pool Filtration — 3 Comments

  1. I have a question. I am renovating a pool (16×32 indoors)- it had a cartridge filter (300sqft). I originally thought it was a sand filter and didn’t look at it that closely. I bought a DE filter. My question is: can I put them inline with the cartridge first and then the DE. Since I already have it I figured why not use it, but I like the filtration of a DE. Thoughts?

    • Hi, you can use two filters, I have never seen it done before, but they can be plumbed inline, sure – water out of one, and into the other. Double the filtration! This should allow you to run the pump slightly less, or use fewer chemicals perhaps. If you do it, let me know how it comes out, and what benefits you notice

  2. Thanks for the tip that if dirt and debris is seeming to make it through your filter than it probably is. I always like to hear common sense solutions to every day issues like this one. It still probably would be a good idea to have a contractor come out and inspect your setup every now and then though.

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