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Sand Filtration – The Benefits

As I’ve written several times in these blogs, I’m a huge proponent of modern water-treatment technology. I believe we’re seeing developments right now that may have far-reaching impacts on how we manage water quality, both in pools and in public utilities and other applications.

With all those big ideas in mind, it may come as a surprise to some that when it comes to the subject of filtration, I fall into the “old-school” category. Specifically, I’m a proponent of using sand filtration as opposed to DE (diatomaceous earth) or cartridges. Here are the reasons why:

First, DE and cartridge filters require ongoing maintenance. DE grids must be cleaned, often repaired or replaced, and the DE itself needs to be handled as toxic waste. Even handling fresh DE is hazardous if it’s inhaled. And, frankly, the process of cleaning a DE filter is simply a miserable chore. It’s disgusting. It also takes time and energy and adds to the cost of maintaining a pool.

Cartridge filters also require cleaning and eventual replacement, granted the process is not as objectionable as cleaning a DE filter, but it does require changing out dirty cartridges with clean ones and putting the used units through a careful process of soaking in TSP (tri sodium phosphate) or another cleaning solution, and then painstakingly cleaning all the pleats. Again, it adds travel, time, and expense to the maintenance process.

Sand Filtration Benefits

Sand is different. It’s cleaned by backwashing, often-automatic backwashing and, therefore, does not require much, if any maintenance. If the pool is managed properly, the sand media can last indefinitely.

Second, the backwashing process adds fresh water to the pool and discards a portion of the old. I’ve long believed, as my friend and pool genius Dave Peterson teaches in his Genesis 3 classes, “the solution to pollution is dilution.” It’s common sense that replacing worn-out water with clean water is a tool, a layer of treatment that stacks the chemistry deck in our favor by getting rid of a portion of all that TDS (total dissolved solids) that builds up over time.

Some people will counter that backwashing wastes water, which is detrimental in areas impacted by drought. Fair enough. On the conservation end of things, however, I can’t help but think that the energy saved by not having to travel to the site and maintenance DE or cartridge filters is a big plus from an ecological standpoint.

And finally, what some people will probably find most surprising is that I see the larger filter micron size in sand filters as an advantage over DE and cartridges. Manufacturers of cartridge filters especially have done a great job reducing the micron size down below five or even lower, and DE has always filtered down to a tiny particle size. By contrast, sand filters remove particulates in the 15- to 20-micron range. So how on earth is that better? Don’t DE and cartridges make for cleaner water?

If you’re using a single-pronged treatment regimen, most typically chlorine, then I would agree, you probably need the small filtration to keep the water clean. But when you have other layers of treatment, such as ozone and UV as we use in our systems, and proper skimming and return circulation with no dead spots, then you don’t need to filter down to such a small size. The entire system is working synergistically and the 15-micron level is more than adequate.

Also, those smaller micron sized filters mean that DE and cartridge filters load up far more quickly. When the media gets dirty, you’re slowing down the flow rate, which will in turn impact heater function, chemical feeders, and overall hydraulic performance.

(As an aside, often when a heater isn’t working, as an example, the cause is a dirty DE or cartridge filter.)

Worse yet, dirty media means you’re actually adding contaminants back into the water. You wouldn’t use a dirty coffee filter to make your morning cup of java; in the same sense, pool water should never pass through media that is loaded with all the material you want to remove in the first place. It’s simply counterproductive and deepens the challenge of maintaining a clean pool.

Those are the reasons I prefer the tried-and-true qualities of sand filtration.

the Water Geek


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A blog about all things water, written by SRK's founder Steve Kenny.