We all know that pool sand filters remove debris from our pool to make it clearer and cleaner, but do we really know what it filters out? If you have a weak stomach, you can just skip the article and chalk the answer down to “stuff” and be none the wiser, but if you’re really interested in learning why pool sand filters are essential to your pool, then read on!

Types of pool water contaminants

Instead of just giving a list of pool contaminants that your pool sand filter handles, we’ll group them into three categories so that it will be easier to identify what certain contaminants are and where they come from. The three are Environmental Contaminants, User Contaminants, and Chemical contaminants.

Environmental Pool Water Contaminants

  • Windblown dirt and debris – This is one of the main sources of pool water contaminants. These include dust, leaves, pollen, and anything that can ride the wind. Larger pieces like leaves and the like are caught in your pool skimmers while those that can slip through the skimmer basket’s holes are removed by your sand filters.
  • Contaminated water – This includes rain, runoff (which grabs on to any ground contaminants) from the rain, and water from unsanitary sources. Contaminated water can bring with it algae spores, bacteria, and other microorganisms that live in water. Your pool sand filters remove the contaminants from contaminated water in concert with your pool chemicals. The chemicals kill all of the microorganisms and your pool sand filter catches their shells or whatever is left after the pool chemicals have done its job.
  • Organic Fertilizer rain – Sorry couldn’t resist. This is just a nice way of saying bird droppings. Even if you don’t catch them in the act, trust us, it’s there. Bird droppings are not only gross, but they can harbor disease causing pathogens. Droppings usually dissipate into the water once they land, so it is very important that your chemical levels are optimal so any pathogen can be killed off at once and so that nothing gets trapped by your pool filter that’s still alive and can colonize it.
  • Dead (and living!) Bugs - Bugs love water and for some reason, they love diving into the pool. Their carcasses are usually big enough to be caught by your pool skimmers, but they may be carrying pathogens with them. Luckily, these pathogens are generally killed off by your pool chemicals and the rest are filtered out by your pool sand filter. If you see dead bugs floating around in your pool, don't wait for them to get sucked into the pool skimmers, scoop them out to give your filter a hand and to prevent decomposition, which may introduce other types of bacteria to your pool.

These environmental pool contaminants are usually biological in nature so it's best to keep your pool chlorine levels up to the recommended levels. To ensure that, always keep some test strips and some chlorine on hand to make sure that you can quickly adjust your chlorine levels and kill off any bacteria and pathogens in your pool so that your sand filter can trap the remains.

Pool User Contaminants

  • Human debris – These include dead (and living!) skin cells, hair, body oils, urine, and other human waste. Believe it or not (or whatever people say) studies have shown that there is an average of 30ml to 80ml of urine for each person that uses the pool. Good thing though that most of these human debris contaminants react with pool chemicals and can easily be trapped by your pool sand filter.
  • Disease and Pathogens – When people with skin conditions or other diseases use the pool, it’s only natural that they shed these pathogens on to the pool. This is another important reason why you should always keep your pool chemical levels where they should be and your pool sand filter in top condition. You want these diseases and pathogens to be killed off and filtered out as fast as possible. Common conditions that may occur when these are not filtered out properly include diarrhea, otitis externa (swimmers ears), respiratory infections, and skin irritation.
  • Cosmetic contaminants – These are pool contaminants that come from what people wear to the pool. Suntan oils, lotions, and even lipstick can contaminate your pool water. While these are marked as “water safe” trust us when we say that these are a major source of contamination for your pool and it’s a good thing that they’re easily filtered out by your pool sand filters.
  • “Accidental” contaminants – These include food, drinks, and other things people bring to the pool and accidentally drop it in. Unsightly as best, but these can also serve as food for other bacteria and diseases so when this happens, give your pool sand filter a hand and scoop them out with a leaf skimmer or leaf scoop before they get stuck in your pool skimmers.

Chemical Byproduct Contaminants

  • Flocculant byproducts – When you “floc” your pool, the chemicals bind with particles (everything that we have mentioned so far) that are smaller than 10 microns so that your pool sand filter can catch them.
  • Mineral byproducts – While your pool chemicals keep your water clean, they also contribute to the contaminants in your pool. Certain chemical reactions produce calcium and other debris (especially if you’re using powdered chemicals that may contain “fillers”) that don’t dissolve fully in the water. The larger particles are removed by your pool sand filter while smaller ones tend to stick to your pool surfaces in the form of a white chalky substance.

Products Featured on this Blog Post


We hope that this post has been helpful in highlighting the importance of having a pool sand filter. If you're in the market for one, or if you're thinking of replacing your old filter system, we highly recommend the Water TechniX Sand Filter Aspire. It's our best-selling pool sand filter and it has a 10-year warranty on the tank so you can be worry-free for the next decade. Don't worry though, it'll last much, much longer than that!

After reading through all that, you may think that it’s too scary to take a dip in the pool, but really, don’t be scared. That’s why your pool chemicals and pool sand filter is there, to make sure that all of the contaminants are filtered out and your pool is safe to use. Remember, there is no way to PREVENT the introduction of these contaminants to your pool, which makes it even more important for you to keep your pool chemical levels up to standard and your pool sand filter always in top condition. Interested in learning more on how Pool Sand Filters Work? Click the button below

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Do you have any questions about this topic or the featured products? No worries, we're here to help! Drop us a question down below and we'll get back to you ASAP.

Happy swimming :)

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