Everything you need to know about Pool Filters

A filter to your pool is like kidneys to your body. Both perform the function of removing unwanted waste and keeping your pool/you healthy. While chlorine and other chemicals kill bacteria and other contaminants in your pool, it’s the filter that actually removes them.

Without a filter, your pool water would become cloudy and filled with unwanted debris. Therefore, a filter is absolutely necessary. So, what types of pool filters are there? What size should you go for? And, how do you choose the best one for you?

Keep reading to find out:

Pool Filter Types:

To make the best choice when you purchase a pool filter, you need to be aware of the different types of filters available and you also need to learn a little about microns. There are three types of swimming pool filters: cartridge, diatomaceous earth (D.E.) and sand filters.

Microns (or micrometres) are a measurement. One micron is one millionth of a meter. To give you a bit of perspective, here are some stats:

• Human hair measures at 50 microns
• White blood cells measure at 25 microns
• Red blood cells measure at 8 microns
• Household dust comes in at 4 microns
• Bacteria can measure as small as 2 microns

When it comes to filters, you need the filter media to be fine enough to actually collect bacteria.

Now that you understand all that, let’s get into the different filter types.

Cartridge filters:

Cartridge filters are an energy efficient, inexpensive and easy to maintain. While some filters require backwashing to be cleaned, a cartridge filter requires you remove the cartridge and hose it down to remove debris.

To really give your cartridge filter a clean, hose it down with filter cleaner and regularly soak it in diluted muriatic acid. This does involve a little more physical work than backwashing a different kind of filter, though it saves more water.

Cartridge filters are great because they can remove bacteria as small as 10 microns, don’t require backwashing, and perform well at lower speeds, making them a great accompaniment to variable-speed pool pumps.

Some drawbacks, however, are that cartridge filters require more physical work than sand filters. They also have a relatively short lifespan, at 2 to 3 years. Also, cartridge filters require a deep clean about twice a year.

Diatomaceous Earth (D.E.) Filters

If you’re a germaphobe then a D.E. filter will quickly become your best friend. Yes, it’s the most expensive type of pool filter, and yes it requires the most maintenance. However, with its ability to remove bacteria as small as 5 microns, it out-performs all other filter types.

So, how does the D.E. filter perform so well? Essentially, it contains grids (sometimes referred to as fingers) covered in coarse white powder made from diatoms. These are essentially crushed fossilised remains of tiny aquatic organisms.

D.E. filters are a pain because you need to add more D.E. powder every time you clean your filter. It’s often difficult to determine how much you need, so it’s best to call in a professional. If you’re still keen to clean your own D.E. filter though, here’s the basics behind how you do it.

Firstly, a pressure gauge on the tank will let you know that it’s time to clean your filter. Next, you backwash the filter. After you filter has been backwashed, it’s then time to replenish the D.E. powder. Also, you will need to disassemble and manually clean the filter at least once per year.

Replenishing D.E. powder

If you’re wondering what the best way to add new powder to your D.E. filter is then we’ve got some info on that for you here as well:

• Mix the powder with water. Add enough water so that you get what looks like a thin, creamy solution.
• Turn on your pool pump. Note: It’s important than it’s running.
• Slowly pour the solution directly through the skimmer rather than applying it directly to the grids. You will achieve much better coverage.

It’s best to do this overnight, as it will take a while for the mixture to integrate with the D.E. filter.

D.E. filter recap

So, let’s quickly go through the pros and cons of a D.E. filter to recap everything we’ve said above. D.E. filters are great because they remove bacteria as small as 5 microns, powder can be added through the filter and chemicals are not required to clean it.

The downside to D.E. filters is that they’re more expensive, require a lot more work to clean, the grids need to be replaced every 2 to 3 years and they’re not quite common for above-ground pools.

Sand filters

It’s finally time for sand filters. The most affordable option out there that also doesn’t require much physical input to clean. If you’ve got a large pool then a sand filter is probably the way to go. They don’t clog quite as easily as the others that we’ve mentioned.

In essence, these filters allow for bacteria to pass through a large internal tank full of sand. The bacteria accumulate in the sand over time and essentially your filter’s internal pressure builds and it lets you know that it’s time to clean your filter by backwashing it. At this stage, the debris will flush to waste. It all seems simple enough.

Here is where things start to look a little less bright with sand filters. Firstly, as time goes on the sand erodes. This means that more bacteria remain uncaptured over time. The other major drawback is that sand filters can’t capture bacteria smaller than 20 microns. Both of these factors mean that you really need to be on top of your pool chemistry.

Overall though, we’d say that the pros outweigh the cons for sand filters. They’re more affordable, require less physical maintenance, and the sand typically lasts between 5 and 7 years before you’re required to change it.

The downside of sand filters is that they’re less effective at removing bacteria, require you to stay on top of your pool chemistry and they also waste more water.

What size filter do you need?

Pool filters and pumps go hand in hand. Neither can function without the other and the sizes for each need to match. The first step you need to take before choosing a filter is making sure that you have the right size pump. See the table below.

Once you have chosen your pump then it’s time to choose you pool filter. Pool filters are rated at gallons per minute (GPM). The filter flow rate needs to be the same as or higher than that of your pump. Again, see the table below for guidance.

If you’re still unsure then contact us via email or call us directly. We sell both pool filters and pumps and have a wealth of knowledge to assist you with making the right choice.