How do Pool Filters Work?

Owning a swimming pool can be something of a double-edged sword – a pleasure for the cool relaxation it provides, but a burden because of the constant maintenance required. If the problem isn’t regular checks of chlorine levels, pH and alkalinity, it could just as easily be the ongoing physical clean-up you need to perform. Most people rely on pool cleaners for the lion’s share of this work, and with good reason – scavenging robots can be surprisingly effective at cleaning the walls, surface and floor of any pool. Even with so many safeguards in place, however, you still need internal systems to pick up the slack.

Pool filters are essential to reliable operation. The truth is that no matter how hard we try, it is inevitable that dust, dirt and debris will make their way into the water of any swimming pool. Leave such unwanted pollution untreated and it’s likely to accumulate rather quickly, creating cloudy water and ideal conditions for an algae population. It is for this reason that every pool sold in the United States comes with a filtration system attached. Which variety you opt for can be as much a matter of personal preference as it is necessary.

How do pool filters work? The basic operation is the same across the board – such filters operate by pumping your swimming pool’s water through some kind of barrier to trap particulates in the solution. Nearly every pool will completely cycle its water through the filtration system several times a day, and some especially busy municipal pools are required to keep the water cycling more than once an hour. Choosing which filter to buy requires that you understand something about the benefits, cost and maintenance regimen associated with each. Knowledge such as this can help you make an informed decision about how much commitment you really want to offer this machine.

There are three major types of pool filter. These are sand filters, DE (diatomaceous earth) filters and cartridge filters. Each is designed to perform essentially the same function, but they get there via different processes. Sand is by far the easiest to own and maintain – and not coincidentally, the easiest to understand. Filters such as these come in tanks that use simple graded sand to catch anything larger than a given size as it passes through. Depending on the type of sand used, that size is generally in the range of 40 microns – well above the threshold for visible dirt and dust.

Cartridge filters are probably the most popular breed, as they offer considerable more flexibility than sand without bankrupting you in the process. The mechanism here is not unlike a coffee filter – water is forced through a paper “fan” under pressure, and the cartridge blocks anything above a set size threshold. Such items can vary, but most fare little better than sand when it comes to particulate size – the very best cannot block anything below 25 microns or so. The great advantage to paper cartridges, however, is that they can be removed and cleaned without backwashing, saving you time and energy.

The most effective filters are without question the DE filters – some advocates have called them the HEPA filters of pool ownership. Specially treated earth made from extremely fine aquatic fossils (diatoms) will filter out far smaller particles than any of the other varieties, often creating a consistent obstacle for anything above 5 microns. The difference may be measurable not just in the clarity of the water, but in its fungal population as well. The trade-off for DE filters, of course, is that they require more frequent backwashing, a fact which leads many homeowners to alternate solutions.

No matter which type of pool filter you choose, it’s important to stay ahead of the maintenance regimen from day one. Problems of algae and fungus inside swimming pools have a tendency to become acute and chronic astonishingly quickly, so it may be worth it to hire additional aid if you cannot make the requisite daily checks. The good news is that regular work and dedication should keep your pool filter operating at peak efficiency for many years to come.

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