For many pool owners, sand isn’t just something to play in at the beach or park—it’s the ticket to a sparkling and beautiful pool. Sand filters are one of the oldest designs of pool filters and have been serving pool owners for decades to great success.
While the intended design of sand filters require them to be filled with silica sand, modern developments have led to options for filling your sand filter with alternatives, each having their own pros and cons.
How a Sand Filter Works
Sand filters are a simple construction consisting of a control valve (often called a multiport valve or slide valve depending on design), an exterior tank, and internal piping collectively called a lateral assembly.
The core of the sand filter, the laterals, are buried underneath the filter media (most often silica sand) with a pipe extending through the media and to the control valve. The control valve also connects to a spray head that sits above the media bed—in sand filters where the valve is on the top of the filter, this spray head is built into the bottom of the control valve.
The basic operation of a sand filter when filtering the pool is: water is sprayed over the media bed, pushes through the media (which is the filtration mechanism), collects through the lateral ‘fingers’, then comes back up and into the control valve as filtered water through the pipe connecting to the laterals.
Filtering happens when the water pushes through the media. The media is stacked on top of itself and makes a very fine sieve with only small holes between the edges of each particle. As the water pushes through these holes, debris and contaminants in the water are caught and filtered out.
Let’s dig deeper into the different options for media.
Silica Sand: The Classic Choice
The good ‘ole standby is #20 silica sand. #20 is a reference to the ‘grade’ of the sand and basically means that the fine, powdery particles have been filtered out and most of the sand grains are all roughly the same size.
Silica sand works great as a filter media as it is durable, moderately long-lasting, and very affordable compared to the other options we’re going to discuss. It’s literally in the name, ‘sand’ filter.
Where silica sand falls short is in its filtration efficiency. At roughly only 20 microns of filtration efficiency, silica sand struggles with very fine particles like pollen, dead algae, and other nasties that can take the sparkle out of your pool!
If you let your pool care get a bit ahead of you, sand filters with silica sand are often the trickiest filters to use to turn things back around—which is why more and more pool owners are turning to sand alternatives such as zeolite.
Zeolite: A Trusted Upgrade
Zeolite, sometimes called zeosand, is a sand alternative that’s been around for some time. It’s much lighter weight than sand, so it lends itself well to those doing their own installation but don’t want to haul and lift 50lb bags of sand.
It provides increased filtration efficiency, somewhere in the 10-12 micron range, which has its filtration roughly equivalent to a traditional cartridge filter.
Once installed, the maintenance on it is pretty much the same as silica sand—you monitor your pressure gauge and backwash as the pressure climbs higher to clean the zeo out. It lasts roughly 5-7 years compared to silica sand at 3-5 years.
Filter Balls: The Lightweight Alternative
A relative newcomer to the sand media option list is filter balls. These fluffy little guys are made of polymer fiber, similar to teddy bear stuffing.
Running filter balls in your sand tank is a bit of a paradigm shift as you do not backwash filter balls! Once added into the tank and put into operation, they compact down to make a firm layer over the laterals of the tank, and the water is forced through the relatively porous polymer fibers.
These fibers catch and hold contaminants in the water, providing the filtration mechanism. Once the balls are fully loaded with debris and no longer providing clear water, they must be removed from the tank and washed in a standard washing machine just like a load of laundry.
Filter balls last on average 3-5 years, just like silica sand.
Glass Media: Premium Performance
If you want the longest lasting option for media, you’ll want to go with my personal favorite—glass media. Glass media is made from recycled glass that is broken down into sand-size particles.
There’s no risk of cutting yourself though! This stuff looks and feels like sand, even when you grind it between your palms. In my time as a field technician, I installed glass media in everything from small above-ground pool filters that are small enough to throw over my shoulder to large format commercial filters big enough for multiple people to crawl into.
Glass media provides excellent filtration at approximately 5 microns, comparable to that of a diatomaceous earth filter. Glass media is rated for 8-10 years, which is the same life as you can normally expect from most sand filters. Some glass manufacturers claim it as a lifetime media because of this (lifetime of the filter it’s being put into).
Maintenance with glass media is similar to silica sand, but with longer breaks between backwashing. With such fine filtration, it gets the water so clear that there just simply isn’t as much debris to filter out in day-to-day operations!
The hardest part of glass media is often sourcing it, as it’s not very commonly found in local pool stores.
Final Thoughts
As we’ve discussed, there are a multitude of options for getting a sand filter tank up and running, each with their pros and cons.
No matter which path you choose to take, proper chemistry balancing and pool maintenance is crucial to a happy and healthy pool all season long. The work you put in as a pool owner week to week works with your equipment and filter to keep things sparkling and beautiful!
