Pool Filters, Explained

A pool filter is necessary for clean water, but which one is right for you?

We have a few choices to make when it comes to filtering our pool water. There are three types of filters to choose from and then several sizes within each type. Remember, these are my opinions only and other people may disagree. I will assume that if you are reading this, you are probably confused by or interested in the different options available. Allow me to shed a little light on pool filters for you.

Pool FilterD.E. Filter (Diatomaceous Earth)

Wow! Diatomaceous, that’s a big word! Regarded by many as the most difficult to maintain of all the pool filters, the D.E. filter actually filters water the best.

Here is an excerpt from Pentair’s product description:

“Diatomaceous earth, or D.E. for short, is a natural substance that traps dirt and debris as small as five microns (1/10 the width of a human hair). That means body oils, suntan lotions, pollens, dust and even some bacteria are caught in a D.E. filter, leaving behind sparkling clear, healthier water. We’ve maximized the filtration area, which means longer periods between cleanings. And we’ve designed our D.E. filters to require the least amount of pumping power to achieve a needed flow rate, lowering your utility costs.”

I completely agree. The D.E. filter will filter out smaller particles than any other type of pool filter. This comes at a cost though, by increasing the difficulty of cleaning the filter significantly. For anyone familiar with a sand filter, the D.E. filter has a backwash valve exactly like the ones found on sand filters. You backwash the filter when it becomes dirty, much like you would with a sand filter. After backwashing, however, you must add D.E. powder back to the filter by pouring it into the skimmer. This powder gets flushed out during a backwash and if not added back, the filter will not clean the water as well and dirt will stick directly to the fabric grids inside, eventually requiring complete disassembly to remove. I recommend to everyone with a D.E. filter to completely disassemble and clean the grid assembly twice a year, once in the spring and once in the fall. This is a major maintenance headache, unless you simply pay someone to clean the pool filter for you. On top of everything else, the D.E. powder itself is labeled as a carcinogen and is hazardous to breathe, so it may filter the water great, but at what cost? D.E. filters are the most expensive filters on the market as well.

  • PROS – Great at filtering the water. Can be backwashed to remove filtered out contaminates.
  • CONS – Requires the use of D.E. powder regularly. Needs to be disassembled to clean occasionally.
  • MY RECOMMENDATION – Keep reading unless you don’t mind paying someone to take care of your pool filter. There are better options for filtering pool water.

Pool FiltersCartridge Filter

When it comes to a cartridge filter, they lie somewhere between sand and D.E. on how well they clean the water. Unlike sand and D.E. filters, they do not feature a backwash valve and this not only means you have to open them up to clean them, but it may pose an issue when you need to drain water (depending on the plumbing configuration).

Here is what Zodiac has to say about their cartridge filters:

“Our filter design takes advantage of the filter’s total surface area, providing you with the clearest possible water and extended cleaning cycles. Enjoy the clear sparkling water of your pool and spa while the CL filter is working for you.

This filter is equipped for high flow rates and optimum hydraulic performance. CL large cartridge filters are constructed of durable, corrosion resistant, heavy duty high-tech polymeric materials for long-lasting performance.

Zodiac’s large cartridge filters are technologically advanced and filled with many user-friendly features.”

Cartridge filters need more maintenance than a sand filter, but they do not require the constant addition of D.E. powder. For me, they fall into a middle position and are good for certain situations, usually smaller pools with very diligent owners. If a pool should ever turn green, good luck clearing it up with a cartridge filter. The constant cleaning of the filter elements will have you very frustrated.

  • PROS – Simple, effective, and easy to operate / maintain.
  • CONS – Must take apart to clean. Filter elements need to be replaced every few years. No way to drain water through a “backwash” valve.
  • MY RECOMMENDATION – Good for anyone maintaining their pool themselves. Easy to understand. Not my top pick, but good for well maintained pools.

Pool FiltersSand Filter

This is the most common of the pool filters and it is common for a very good reason; it is easy to maintain. A sand filter is a tank full of sand, through which the water is forced, thereby trapping any debris. A sand filter actually filters worse than the cartridge or the D.E. filter, but this is not a deal breaker. In my many years of experience, I notice little to no difference in water clarity between all three filters when the water is properly balanced and maintained correctly.

Hayward’s two cents on sand filters:

“Pro-Series high-rate sand filters are the very latest in pool filter technology. Molded of durable, corrosion-proof reinforced thermoplastic, Pro-Series filters feature an advanced, self-cleaning lateral under drain system for smooth, efficient flow and totally balanced backwashing.”

The sand in a pool filter will typically filter well for at least five years. Many sand filters will filter correctly for more than five years and there are chemicals that can be used to clean the sand. The sand itself does not break down or become ineffective at filtering, but oils and other filtered material can cause the sand grains to stick together, making the filter less effective over time. Even if a sand change is necessary every five years, this is less maintenance than cleaning a cartridge or D.E. filter a couple of times a year. If you had not guessed, the sand filter is my favorite pool filter. With the ability to backwash dirt out of it, drain water when needed, and less regular maintenance than the other options, it is a winner. The price is affordable too.

  • PROS – Easy to maintain and very affordable.
  • CONS – Does not filter as well as other options. Requires cleaning of sand with chemicals or sand change after approximately five years.
  • MY RECOMMENDATION – This is the only filter I would use if it were up to me. The sand filter strikes a perfect balance between being user friendly and ease of maintenance.

An Atlanta area native, Shawn began servicing pools in 1998 and has not stopped. Years of experience have provided Shawn with a wealth of knowledge and opinions about all types and brands of pool equipment.

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