Currently, the best pool filter type on the market, in terms of unmatched filtration, is a Diatomaceous Earth filter (D.E. Filter). Unfortunately, if you’re not careful, there’s a chance it could end up being dangerous to your health. The diatomaceous earth in these filters is not food-grade but is both heat and chemically treated. Additionally, the D.E. filters also require more maintenance and cost more.
The answer to the question, “Which type of pool filter is the best?” isn’t straightforward because it depends on what is most important to you. If you want a general well-rounded filter that is easy to maintain, you should probably go with a cartridge filter. However, it will not work for the larger pools...but let’s get into that later. We just wanted to emphasize the point that choosing the best filter isn’t straightforward. It isn’t difficult either. You just need to know a few things before making the choice.
Without further ado, here’s a quick-fire list of some of the basic features and then we’ll get more detailed after that.
|Pool Filter Type||Sand||Cartridge||Diatomaceous Earth|
|Average Cost (Above Ground)||$200 to $300||$500 to $1,000||N/A|
|Average Cost (In-Ground)||$500 to $800||$250 - $550||$500 to $1,500|
|Smallest Average Particles Filtered||20 microns or larger||10 microns or larger||5 microns or larger|
|Filter Lifespan||5 to 7 Years||2 to 5 years||2 to 3 years|
Depending on the make, model, and size of the filters, pool size, and the environmental conditions such as heat, humidity, and debris, you could find how often you need to clean and replace filters will differ from what is listed below. What we have listed below are the general recommendations for these types of filters.
The diameter of a human hair is 70 microns, a white blood cell is 25 microns, and bacteria is only 2 microns. There are some D.E. filters that claim they can filter down to the 2-micron level, but confirming those uncommon claims is difficult. Whether they can or can’t, these filters are still screening out some impressively small objects.
Algae is Too Small for Filters
Algae is a common enemy for many pool owners. Filtration systems have a very difficult time filtering them out because algae can be as small as .1 micron to as large as 15 microns. That means that sand filters will hardly have an effect since they are rated for 20 microns and larger. The other filters will have an impact, but none of them will offer anything close to perfect protection.
Protecting your pool from algae will come down to knowing how to balance your pool water chemicals. That is going to be the most important factor for this particular contaminant. If you don’t know how to do that, we have another guide that can help you get started.
5 to 7 year lifespan
Easy to clean
Filtration efficiency can be boosted with alternative sands
Backwashing dilutes pool chemicals
Most filter sizes of 20 microns or larger
Need to be careful how you dispose of backwash water
Needs frequent backwashing and rinsing
These are the budget filters that use the most primitive of filtering technology. If you’ve ever seen someone in a survivor show put a heap of sand and rocks in a bottle and let the water run through to make the water drinkable, it is essentially the same thing.
These hollowed-out tanks are filled with one of three types of sand: silica sand, zeosand, filter glass. As the skimmers pull in water from the pool, that water is pushed through the sand in the filter’s tank by the pool pump. Anything 20 microns or bigger is trapped in the sand, but the water easily passes through it.
Silica vs Zeosand vs Filter Glass
There are three types of sands that you can use in a sand-based pool filter. Silica is considered the basic or standard sand, but that certainly doesn’t mean that it’s the best.
|Smallest Average Particles Filtered||20 microns||5 microns||9 microns|
|Longevity||Lasts 3 to 5 years||Lasts 5 years||Lasts 10+ years|
Silica sand is a great medium for this filtration work thanks to its jagged edges that catch the various contaminants infiltrating your pool. Over time the edges are polished smooth and they lose their ability to latch onto the pollutants. When this happens the sand will need to be changed.
As you can see from the chart above, this doesn’t happen very often. This makes the sand filters economical from both maintenance and entry standpoints. The longevity and filtration capabilities of the different types of sands can vary from what is listed above. Use the chart as a guideline of expectations of these three products.
Sand also comes in the form of zeolite. It’s a lightweight mineral that is about half the weight of the standard silica sand.
It’s also capable of catching smaller contaminants than silica which improves the clarity of the pool's water. The improved filtration is thanks to its crystalline shape and its vastly increased surface area that is 100 times greater than your standard sand.
With silica sand, a lot of the particles will end up being trapped between the grains. This plugs up the line and increases the pressure. In contrast, the crystalline shape of zeosand has an increased capability to catch the contaminants upon its edges. Because fewer contaminants end up between the grains, water continues to flow through for longer. This means fewer backwashes.
This product is made from recycled glass; worn down to a smooth texture that is safe to the touch. Its slightly negative charge is where it gets its superior 9-micron filtration capability. According to some claims, it can filter as small as 3 microns.
There was a 9-month study performed by the Clean Washington Center that was quite helpful in determining some of the strengths of glass sand. According to this study:
Shifting Filtration Capabilities
One odd but beneficial effect of these filters is that the contaminants trapped in the sand can help to filter additional and potentially smaller contaminants. This benefit won’t outweigh the inevitable decline, but it does make the efficiency of the filtration system change over time in the shape of a bell curve. It’s a nice benefit. Albeit it’s an unexpected one.
Backwashing and Chemical Balancing
Some people say to backwash sand filters once per week and others say that pools only need to backwash once or twice a year. Additionally, some people say to backwash when the pressure gauge registers an 8 PSI increase. Others say to wait till around 20 PSI.
The reason for this is that the right and wrong answer, once again, depends on what is important to you. Do you want to maintain optimal filtering efficiency? If you do, it means you will need to backwash your pool. It will cost money to replace the expelled water and to rebalance your pool chemicals.
Operating Valve Isn’t Always Included
If you’re going to buy a sand-based pool filter, pay attention to more than just the basic capabilities of these filtrations systems. Keep an eye on whether a multi-port operating valve is included or not. It will be most of the time. However, if it’s not, you will have an additional $100 expense that you will need to pay. You’re going to need one of those, so don’t let it catch you off guard.
DE Powder Trick
If you want to increase your pool filter’s capabilities, try adding some D.E. powder onto the filter’s sand. It can work quite well. However, be sure to take precautions. As we’ve briefly mentioned, D.E. powder can cause cancer if inhaled. It’s not something to mess around with without care.
There are three types of filtration systems
Easy to clean
Filters contaminants as small as 10 microns
Performs well at low speeds
Wastes less water
Can be expensive
Deep cleaning is required twice per year
Lasts 2 to 3 years
Requires more maintenance than sand filters
High flow rates push contaminants through the filter
Cartridge filters are a fantastic choice for small to medium pools. The above-average filtration capabilities paired with the low cost and easy maintenance make this the common choice for many homeowner’s pools. Most of the time, this is the one that we are going to recommend.
Cartridge Filters Only Work on Medium to Small Pools
Before we get into all of the good, let’s delve into the downside. These filters do not work well with pumps that have high flow rates. High flow rate pumps are needed for larger pools. The pressure from these pumps can push the contaminants straight through the filter and right back into the pool.
To prevent this potential problem, you should read the packaging and consumer reviews to find out what amount of pressure your specific cartridge can handle. As long as you stay within those confines, you shouldn’t have any issues.
Large surface area
Although the plastic tank is smaller than a sand filter’s tank, the pleated design of polyester cartridge filters is spatially efficient. They provide a very large square footage that is unbeaten by its counterparts. The increased square footage means that the filter has more space to capture the various contaminants that flow through it.
Inexpensive and Easily Replaceable
If you’re looking for a filter that can fit a smaller budget, this might be what you need. The cheap initial costs paired with the cheap prices of replacement filters will make this a very economical choice.
Easy to Clean
Cartridge filters need to be cleaned at least twice a year, probably more. Just keep an eye on the PSI and it’ll let you know when it needs a cleaning. The process is relatively simple. Pull the cartridge out, wash it down with a hose, and soak it in a container partially filled with water and either a cartridge cleaning solution or some muriatic acid.
Unlike sand and D.E. filters, cartridge filters do not require backwashing. Instead of dumping water on full blast for several minutes, you can use a regular hose to wash out the pleated folds of the pool filter.
Easy to add additional D.E. powder through the skimmer
Filters contaminants as small as 5 microns
No caustic chemicals are needed for cleaning
It is a caustic chemical
Requires a backwash valve
Annual cleaning takes a lot of work
Filtering grids must be replaced every 2 to 3 years
Hard to find for above ground pools
Local ordinances might restrict backwashing
If you want pool water as clear as crystal, you want a diatomaceous earth pool filter. It is unquestionably the best at what it does. On average, it can filter particles as small as microns. Some say that these filtration systems can filter to sizes as small as 2 microns. That is an impressive claim and would mean that they are capable of filtering bacteria.
Cleaning days for D.E. filters can be problematic. Before making the purchase, you should be aware of the environmental and financial problems. There are also potential local regulations
Difficult to Clean
These pool filters take a bit more effort to clean.