Filtration Nation

Eric Herman Headshot
photo of person letting swimming pool water run through their hands
Flickr | Kip Martin

Although filters and filtration are most often associated with aftermarket/service concerns, it’s almost always the builder who selects the filter to be used on a given pool or spa, whether during the initial installation process or as part of a major remodel.

Servicers may come along and make changes down the line, but most often they’ll replace like with like for convenience sake; so the builder’s initial selection is crucial.

With that in mind, we contacted a handful of prominent builders and asked them what criteria drives their choice when it comes to setting up the filter and overall circulation system. They all cited a number of key issues involving overall circulation design, skimmer placement, filter sizing and plumbing layout and sizing.

Given such a broad spectrum of factors, for our purposes here, we’ll tackle two key issues: type of media and filter-cycle run times, all with the caveat that superior water quality relies on a range of interrelated factors.


One theme that consistently comes up when discussing filtration with builders is that, relatively speaking, pool and spa filters with their three basic media choices — sand, diatomaceous earth and cartridge — have not changed that much over the years, with a handful of exceptions.

According Pete Cattano, president of Paco Pools in Baldwin, N.Y., a builder with nearly four decades of experience, “In general, our industry has been very non-inventive. The filters we have in the pool and spa industry, whether sand, DE or cartridge, are all technologies that have been used prior in other industries. There’s very little that we can point to that we can say is purely from the pool and spa industry. The technology hasn’t changed much.

“What has evolved,” he says, “is the way we think about and apply these technologies.”

To a large extent, the type of filter used has in the past been seen through a regional lens, with some media types dominating in an area and then for various reasons transitioning to another.

“Southern California has long been known as an area where D.E. has been the most prevalent type of system,” recalls Randy Beard, president of Pure Water Pools in Costa Mesa, Calif., and a former service technician. “I think it was chiefly due to the low micron level; it was promoted as a superior form of filtration, suppliers started stocking and selling large number of D.E. filters and it became the norm. But times change and in recent years cartridge filters have become more widely used because they’re much easier to service and don’t cause some of the headaches you experience with D.E.”

(For more discussion on pros and cons of D.E., see the side bar on this page.)


While builders contacted for this discussion shared very different reasons for their preferred choices, the end goal of creating a positive consumer experience remains constant. In that spirit, these builders agree that the different filter types can all be used effectively, depending on environmental conditions and other relevant factors.

“In some respects,” Beard says, “it’s really kind of a wash for us in that it really doesn’t make all that much difference if we put in sand, D.E. or cartridges; they all work when installed with a well-designed circulation system and are serviced properly. Most clients don’t even want to know what kind of filter medium they have, they just want their pools to look great and be ready for use at a moment’s notice. Their attitude is, ‘Don’t tell me about the labor pains, just show me the baby.’ They want a clear and clean pool and that’s it. You can achieve that with any of the three filter types, so long as the entire system is designed and installed correctly and the pool is well maintained.”

With that qualified ambivalence in mind, what criteria does Beard use when choosing a filter system? “These days, we’re installing cartridge filters, largely based on what I’m hearing from our start-up service companies, which end up servicing most of our pools going forward. If they’re happy,” he says, “they’ll keep the customers happy.”

While serviceability is key, cartridge filters also present an attractive profile in terms of hydraulic performance, says Kevin Woodhurst, president of Precision AquaScapes in Phoenix, Ariz. “I’m using 99.9 percent cartridge filters. They have the most favorable flow characteristics, which in turn enable us to take advantage of the pump performance, or in other words, find the ‘sweet spot’ where the pump is operating efficiently at the lowest speed possible. Do they clean down to the same micron level as D.E.? No, but they do filter to a level that it supports great water quality.”

Those persuasive arguments don’t hold sway with all builders, such as Cattano, who favors high-rate sand systems. “I will use cartridge filters, but I still prefer high-rate sand filters because they’re very user friendly. On the negative side you do have to have a place to send backwash effluent and that’s not always available on some jobs. In those situations, we’ll opt for cartridge filters.”

Although Cattano appreciates the enduring reliability and ease of maintenance that comes with sand, he quickly adds that he’s adjusted his approach in recent years. “Rather than using sand, I use zeolite media in a sand filter. Zeolite takes you down close to DE in terms of micron retention, so you’re going to get sparkling water, and we’ve found that it also gives you longer filter cycles, so you’re backwashing less often. It’s kind of the best of both worlds.”

The issue that drives Cattano away from cartridge filters? “They’re a royal pain to clean,” he says. “You’ve got to pull the filter apart, take the cartridges out and get between all those pleats to remove the dirt. Also, with cartridge filters there’s an issue called ‘interstitial embedment,’ which means that over time dirt will migrate in the interstices of the filtration medium. It gets to the point that there’s so much blockage that the filters lose all their efficiency and that’s when you have buy new cartridges.”

Also preferring sand filters is Steve Kenny, owner of SRK Pool Services, a builder and service firm located on Long Island, N.Y. “Sand filters will take out particulate down to the 10 to 20 micron range,” he says. “If you’re sanitizing and oxidizing properly and maintaining balanced water, that range is more than adequate and I argue going below 10 microns is overkill.”

Kenny adds: “Backwashing weekly or every other week is not necessarily a bad thing, because as Dave Peterson of Genesis 3 says, ‘the solution to pollution is dilution.’ It’s common sense: backwashing helps to maintain superior water quality partly because there’s a level of routine dilution. You’re cleaning the filter regularly and diluting the water, which keeps TDS down and prevents the build up of various chemical levels that can become problematic.”

By contrast, in regions where water shortages are an issue, such as California, Arizona and Texas, the cartridge filter concept is often favored precisely because it doesn’t require backwashing. “In areas where drought and water-supply are issues,” Woodhurst says, “I like the fact that with a cartridge filter you’re not sending 500 or 600 gallons of water to waste through backwashing. That’s more and more important as we’re coming into an age where we’re trying to conserve resources, whether it’s electricity, water, chemical consumption or by way of construction standards.”


The selection of the filter type is only one element in achieving efficient and effective filtration. Another is the length of time the system runs and at what flow rate, an issue that nowadays transcends basic turnover calculations.

“How we think of turnover rate has evolved,” Beard says. “Certainly with commercial pools you need to achieve the six- or eight-hour turnover rate as defined by health officials, but the concept in residential pools has changed. Yes, we do want to turn the pool over, but the real goal is to maintain constant filtration so you’re not seeing fluctuations in water quality.”

With that in mind, Beard notes that the advent of variable-speed pumps has been a game changer when it comes to designing treatment regimens with extended circulation run times in mind. “With variable speed,” he explains, “clients can run their systems for longer periods, at a lower speed and reduced energy consumption. The water is being filtered longer, more slowly and it stays cleaner, which means we can scale back on the chemical treatment.”

And that has led to a transformative change in his approach to chemical treatment: “If a client is willing to run their system 24/7, and many are due to the reduced energy consumption of the VSP pumps, then we’ll install a UV system and attempt to go chemical free.”

Beard admits that although going sans chemicals represents a huge departure from standard industry practice, it’s a worthy aim given growing client anxiety about chemical usage and societal trends toward environmentally favorable approaches. “So far, we’ve had pretty good luck with it,” he reports. “At the very least, we’re certainly able to drastically reduce chemical consumption.”

For his part, Woodhurst has developed an entire system-design approach based on the concept of maximizing filtration and circulation while minimizing chemical consumption, an approach largely based on extending filtration cycles: “I’ve been an advocate of 24-hour circulation for 16 years,” he says. “My belief is that too many pools are medicated with chemicals rather than filtered properly. What happens is people make up for not running their system long enough by adding unnecessary chemicals, which cost substantially more than the electricity required to achieve proper filtration by running the pump at a low speed.”

According to Woodhurst, it’s all a matter of pure common sense because by extending filter times, “you’re dealing with less particulate, less material that fuels bacteria and algae growth, and you’re not having to use chemicals to oxidize those compounds.”

The D.E. Conundrum

As you may have noticed reading the adjoining text, all of the builders interviewed for this discussion prefer either sand or cartridge filtration, none cite D.E. as their favorite. (No doubt a broader sampling of builders would reveal those who do prefer D.E.)

Interestingly, these and other builders acknowledge that D.E. provides the finest level of filtration commonly available to the industry with filtered levels down in the 1 to 5 range and for many years has been a dominate technology in many regions of the country. On the other hand, they are all quick to point out D.E. has a problematic or even a dark side that makes it the most difficult of all pool and spa media to service.

“D.E. is considered by many to be a material like asbestos in that you don’t want to inhale it, and there are all the issues about disposal,” says Cattano. “It’s really messy stuff and not something most people want to handle. I’ll install it if the client insists, but otherwise we prefer either cartridge or sand because they’re so much easier to maintain.”

Beard agrees: “Different jurisdictions have differing rules governing how you dispose of the used D.E. I talked to one city official that said the right way to do it was to use the clients’ showers to wash it directly to the sewage system. That took me by surprise and I was skeptical because that means putting tons of the material through sewage treatment plants. It’s not at all clear officials from those facilities are in favor of that plan. It can be a confusing issue.”

In addition to handling and disposal issues, builders such as Kenny believe even D.E.’s high level of filtration can be problematic: “I’ve found that the media loads quickly and can short cycle, which creates all sorts of headaches.“

That said, Kenny also concedes, “I wouldn’t say that D.E. should never be used. The three media types are all tools and like any type of tool there are going to be applications where it makes sense.”

No doubt, advocates of D.E. would be more than happy to expand on that point.

Comments or thoughts on this article? Please e-mail [email protected].

Content Library
Dig through our best stories from the magazine, all sorted by category for easy surfing.
Read More
Content Library
Buyer's Guide
Find manufacturers and suppliers in the most extensive searchable database in the industry.
Learn More
Buyer's Guide