What Does A Pool Filter Remove? (Salt Water Pools)

What Does A Pool Filter Remove? (Salt Water Pools)

A pool filtration system is an important part of any swimming pool to keep it clean for swimming. The pool filtration system removes impurities and debris and while the actual filter unit itself is often regarded as the “filter” on its own, there are actually several key components that pool owners should know about.

For the purposes of this article and following list, we’ll define the filter as the entire filtration system including the side skimmer, pump basket and the filtration housing and filter medium itself. We’ll also discuss what purpose each part serves.

Your pool filter system will typically attract and remove the following impurities and debris from the water:

  • Leaves
  • Twigs
  • Sand
  • Dust
  • Dirt
  • Algae
  • Worms
  • Bugs
  • Silt
  • Oils
  • Hair
  • Dead rodents

Let’s take a closer look at your pool filter options and how they help to clean your pool. We’ll also give some tips on choosing the right one for you.

What does your salt water pool filter do?

Your pool filtration system is comprised of three main parts that remove impurities from the pool water to keep it clean for swimming:

Side skimmer: Located on the side of the pool typically around the center, this is the little white flapper thingy you see opening and closing to trap anything floating on the top of the water such as hair, bugs, twigs and leaves. When the pump is running, it draws water off the surface and skims the water, hence the name skimmer. Dead mice or other rodents also often end up here. I once found a partial roof shingle lodged in my side skimmer following a heavy wind storm.

Pump basket: Located near the pump, the pump basket has a clear plastic top that can see through and a removable plastic basket that traps larger items such as bugs, worms, twigs, bit of leaves and things of that nature, that somehow made it past the side skimmer or that got sucked in from the main drain at the bottom of the pool. The suction is strong so you’ll be surprised how large twigs can get sucked all the way through! The pump basket prevents this junk from entering the filter unit.

Filtration unit itself: Typically just referred to as the “pool filter” this is the final stage of the filtration system. Water enter the filter after going through the pump basket and it tends to trap the smallest particles like dust, dirt, bugs, algae, hair and other impurities that somehow made it past the skimmer and/or pump basket. Algae also tends to end up here too if you have it in your pool.

When you read the expression “filter medium” it’s referring to the actual part of the unit that removes the debris. Filter mediums include sand (sand filter), cartridges (cartridge filter) and diatomaceous earth (D.E. filter). We’ll discuss each in more detail below.

Which pool filtration system should I choose for my salt water pool?

First off, it’s important to note that you can choose the exact same filtration system for your salt water pool as you can for other pools. The buying decision largely comes down to how much you want to pay and how much time you want to spend maintaining (i.e. washing/cleaning) your filter.

Here are the popular types of pool filters that are widely available along with their price level:

  • Sand pool filter (lowest price)
  • Cartridge pool filter (medium price)
  • D.E. pool filter (highest price)

The list of three filters above is also in order of which ones best filter the smallest size particles from worst to best. So D.E. filters are most capable of removing the smallest particles and sand filters are least capable with cartridge filters in between.

You can read my complete article on pool filters but here’s a quick and dirty concerning the key differences and benefits of each:

Sand filter: Least capable of filtering out very small particles. The cheapest option and the oldest technology. Water passes into the filtration system and sand filters out impurities. Sand filters must be back washed which involves rinsing it out by effectively running pool water through the medium until the water runs clear. This involves work on your part and also water loss which must be replaced.

Not all municipalities allow you to back wash into public sewers so check ahead of time before buying one! You normally run a hose from your pool pump out the front yard or driveway and drain the water during back washing.

You also have to replace the sand entirely perhaps every 3-5 years.

Cartridge filter: Better than sand filters at filtering out very small particles. From personal experience, these are pretty good with less maintenance as back washing is not required. Cartridge filters use pleated drums (cartridges) that hold the debris and keep it from reentering the pool. The image at the top of the article shows three dirty cartridges in need of rinsing.

Maybe 1-2 times per year you need to take the cartridges out from the filter housing and rinse them but maintenance is pretty easy otherwise.

Cartridges might last around 3+ years before needing to be replaced. They are a good choice for pool owners in my experience as they’re better than sand filters with less work and unlike the other two options listed here, involve no back washing.

D.E. filter: Best option of the three listed here for filtering out the very finest and smallest particles. D.E. stands for diatomaceous earth and it’s this powder than assists in filtering out particles from your water. These filters additionally contain grids to hold the D.E. powder and these grids do need to be rinsed regularly. They will eventually need to be replaced when they wear out, too.

You also need to replenish the D.E. powder as it decreases from back washings. D.E. filters like sand filters need to be back washed when required – usually about once per month – and they are the most expensive pool filtering option.

Reducing the contaminants and debris in your pool filter

In order to reduce the amount of junk in your skimmer, pool basket and filter system, you need to reduce them from your pool water full stop.

There are a few things you can do to limit the contaminants and debris in your pool by doing the following:

  • Have a quick shower with soap and rinse off before going swimming. You’ll remove deodorants, body oils, loose hairs and other things that will otherwise end up in your pool.
  • Use a pole skimmer to pull leaves and other floating debris out of the pool before it gets into the side skimmer. After a wind or rain storm is when you often end up with leaves and other debris in your pool and that’s a great time to skim the water manually.
  • Brush the sides and floor of your pool regularly with a brush on a telescopic pole to loosen algae or other dirt so that it goes into the filtration system and out of the pool water.
  • Keep your dog or other pets out of the pool. Pet hair and dander will end up in the skimmer and eventually the basket or filter mediums too.
  • Check your side skimmer and pump basket several times per week and empty them as needed. I’ve seen the basket get pretty heavy with wet leaves and the like which can impact pump performance.

You can also keep the area around your pool tidy by sweeping up and removing dirt, soil, twigs, leaves and other debris that can fall into the pool.

Carl Mueller

I bought a home with a salt water pool in 2006 and soon realized the benefits over traditional chlorinated pools. On this website I'll discuss all the tips and tricks I've learned over the years. I'll also help you troubleshoot various problems with pools in general and ones specific to salt water pools that I've experienced personally!

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