Pool filters are essential to the operation of any pool. Without a pool filter, your pool wouldn’t be able to remove contaminants from the water and would rapidly turn cloudy and become unusable.

There are three main types of pool filters; sand, cartridge, and DE. Today, we will discuss the advantages and disadvantages of all three to help you decide which is best for your pool. First, however, we will discuss a term that comes up all the time when discussing pool filtration; microns.

What Exactly Is A Micron?

A micron is simply a measurement of size. One micron (short for micrometer) is one-millionth of a meter. To give you an idea of scale, a single human hair is around 50 microns thick.

Pool filters commonly rate their filtering ability in microns. This number is the size of particle that the filter is able to effectively remove. While some particles that are smaller than the rated size will be filtered out, the majority will simply pass right through the filter.

For example, sand filters are typically rated to effectively remove particles that are 20-40 microns or larger. This means that most 50 micron particles will be removed by the filter the first time the water passes through it, while the majority of 10 micron particles in the water will simply pass right through. While the sand filter might eventually remove a significant amount of the 10 micron particles in the water, it will never be able to remove them all and as a result, the pool will turn cloudy more easily.

Sand Filters

The most common type of pool filter is the sand filter. Sand filters use silica sand to remove particles from the water. Silica sand has many jagged peaks and valleys (think tiny pieces of broken glass). As water passes through the sand, debris is caught in the “valleys” of the sand.

Eventually, the sand in sand filters becomes too full of debris to effectively filter the water. When this happens, the sand filter needs to be “backwashed”. Backwashing reverses the flow of water through the sand filter. This allows all of the trapped debris to be released from the sand and sent out of the pool through the backwash line.

While the backwash process is effective at cleaning the filter, it also means that you will lose some water that then needs to be replaced. The pool water will then need to be rebalanced with chemicals to ensure that it is safe and comfortable to use.

While sand filters are the cheapest pool filter to buy and most familiar to most pool owners, they are also the worst in terms of their filtering ability. At best, silica sand is only able to filter down to around 20 microns. This allows common contaminants like pollen and dead algae to pass right through the filter; requiring a ton of time, effort and expense to fix certain water clarity issues. The jagged edges of the silica sand will also wear down over time, reducing the filter’s effectiveness over time.

Advantages Of Sand Filters

• The cheapest type of pool filter available.
• Easy to operate and maintain.

Disadvantages Of Sand Filters

• Don’t filter the water as well as other pool filters (only 20-40 microns).
• Sand becomes less effective over time and needs to be replaced.
• Backwashing can throw off your water balance.

Cartridge Filters

These pool filters use large cartridges to filter the pool water. These cartridges are made up of several layers of interwoven paper webs. As water passes through the filter, particles are trapped in between these paper layers. Due to their tight interwoven design, cartridge filters are able to filter down to around 10 microns; effectively filtering out everything except for certain types of pollen.

Over time, the cartridges will become saturated with trapped particles and will need to be manually removed and cleaned. Under normal circumstances, this will only need to be done a few times a year. If the pool is experiencing a problem with cloudy or green water, however, you may have to clean the cartridges every couple of days.

The cartridges will also need to be replaced every 2-3 years, which can be quite expensive for some models of filter.

Advantages Of Cartridge Filters

• Filters the water better than sand filters.
• Lower chemical and water costs because there is no need to backwash.
• Easy to clean.

Disadvantages Of Cartridge Filters

• Replacing the cartridges can be expensive.
• Can require a lot of maintenance if the water turns cloudy or green.

DE Filters

Diatomaceous Earth (“DE”) filters use a series of grids coated in diatomaceous earth to filter pool water. DE is a naturally occurring rock that can easily be crumbled into a fine white powder consisting of individual particles that can be less than 2 microns wide. Because DE powder is so fine, it is able to filter pool water down to a 2-5 micron level. This means that DE filters are easily able to remove any contaminants found in pool water.

DE filters do require a little more work to clean and maintain than other pool filters, however. Like a sand filter, DE filters require regular backwashing to keep the filter clean. Unlike sand filters, however, the DE is actually removed with the trapped contaminants. This means that you have to add more DE to the filter each time that you backwash. You also need to be careful about how much DE you add to the filter as too much or too little will negatively affect the filter’s performance.

DE filters are also typically the most expensive pool filters on the market, although they are by no means unaffordable.

Advantages Of DE Filters

• The best filtration ability.
• Relatively low maintenance cost. Grids can last for many years if well cared for.

Disadvantages Of DE Filters

• High purchase price.
• More complicated to maintain.

So Which Pool Filter Is Best?

So which pool filter is best for your pool? The answer really depends on your circumstances.

If you’re already comfortable using a sand filter and your pool doesn’t experience too many green or cloudy water issues; a sand filter can be your best option. In this case, the sand filter’s low cost and ease of use will often outweigh the odd time that you will need to spend more time and money fixing a green or cloudy pool.

If your pool does experience water clarity issues more frequently and you’re tired of always needing to add chemicals and backwash your pool to fix them; a cartridge filter is likely the best pool filter for you. As long as you maintain a good level of chlorine in the water, your pool should never really turn cloudy or green if you use a cartridge filter; unless you have a pollen issue.

Pollen is a growing problem with pool owners in certain areas. While it doesn’t pose a risk to humans, pollen can quickly turn a pool green. It isn’t affected by chlorine and is too small for most pool filters to be able to deal with. If your pool experiences a lot of issues with pollen, a DE filter is the best choice for you. They are the only pool filters that are able to effectively filter out pollen without the use of multiple chemicals and days if not weeks of work.