The more things change, the more they stay the same. Hot tubs have changed a lot over the last few decades. Simple, rustic, tubs have evolved into high-tech, multi-featured spas. Materials such as acrylic, Lucite and fiberglass have replaced redwood or cedar. Jets are fancier, more plentiful and more complex. Sanitization has evolved to include more ozone and UV and less reliance on chemicals. And spas can now be as fully accessorized as any self-respecting minivan.

But one thing that's changed little since it was first put into production is the material that makes up the inner workings of a cartridge filter. And that fact is a pretty good indicator of just how well the material performs. "Reemay is the standard fabric," says Sam Collins, vice president of manufacturing for Marquis Spas. The continuous filament, spunbond polyester, manufactured by BBA Fiberweb Filtration, has a 30-year history in the industry, and the biggest changes over the years have been in the amount of Reemay that manufacturers can pack into a filter, not in the material itself.

"We use a material today that is similar to what we used years ago," says Collins. Heather Finley at Sundance agrees that the basic material has needed little change, "In recent years, most improvements have come in the form of enhancements to existing materials."

Look At Me!

Spa manufacturers spend a lot of time and resources trying to stand out from the crowd. With that crowd numbering in the dozens, it's a dizzying prospect for consumers trying to decide which tub to buy. But regardless of how many bells and whistles a spa has, if the water isn't clear, clean and inviting, customers will feel like they wasted their money.

Filtration is a multi-faceted, if not complicated, thing — dependent on the perfect balance of filter media, filter size and design, plumbing and pump selection — but it's not as glamorous as jets, audio equipment or lighting. "Does that filter have spunbond continuous fiber in it." isn't usually among the first things a customer asks, but it probably should be.

"We produce filter media with 'continuous' fibers, so you don't get loose fibers coming off the filter," says Frank Baker, senior marketing manager for BBA Fiberweb Filtration. "For example, a poly-cotton blend is made of chopped up fibers, as are some of the particulate materials. The continuous fiber has less propensity for the fibers to be lifted on the surface. They will stay flat and make the filters easier to clean." But not every salesperson knows that, and even fewer consumers do.

"We're hoping to educate the consumer about the need to explore and ask questions about the qualities of a filter, because in most cases you won't know the difference from the package," says Baker. "There's nothing to help you make a choice. There's really nothing out there to help direct a consumer to a premium filter."

"The typical filter has a lot of commonalities, no matter who you go to," says Collins. "You can have different weights of filter media, but everyone pretty much uses the spunbond polyester, the Reemay-type material. They only differ in outside design. Typically there's a core, and then uerathane end caps. The filters are held in place differently — some screw in to a fitting, others are held by pressure, but if you were to take them all out and line them up, they would be very much the same."

More With Less

So the challenge for each spa manufacturer is to offer a better, more unique filter while using the same reliable spunbond polyester. And filter manufacturers are asking the filter media manufacturers to help with that. "They are seeking media that help differentiate their brand," says Baker. "'Something different, so I can be unique,'" is the request he frequently hears.

Perhaps the most notable enhancement to cartridge media has been the addition of a microbe-repelling substance to the Reemay product. "You put an antimicrobial material such as Microban into the filter — and it has to be on the surface of the fiber," Baker says of Reemay Advantage, his company's antimicrobial media. "The microorganisms come in contact with the active agents, which disrupt the bodily functions of the microorganism. This is not a chemical reaction and is not toxic." According to Baker, the Microban prevents microbes from establishing growth on the filter media. Chemicals are still needed to sanitize the water, and the structure of the Reemay fabric still does its job of excluding particles down to a certain size. "Once customers learn about the value of an antimicrobial filter, they want it," says Baker.

But Collins isn't so sure its right for his product. "There have been some additives that have been advertised as 'aiding filtration,' but we don't do that or promote it, because we can't really prove that it does anything better than what the filter itself can do. There again it comes down to chemicals. What are you really trying to filter? Dirt? Debris? Body oil? Or are you trying to do something chemicals are better suited to doing?"

Finley of Sundance is also quick to point out the primary function of the filter media. "We are seeing more and more filter materials that are available with special treatments to handle other tasks, but the primary function of removing suspended solids from the water should not be overlooked," she says. "Chemical treatment of the water will still be necessary."

Multi-tasking Tech

With today's exponentially increasing level of technology, many things are now technically possible. "Fungicide, algaecide, innovative things that make it more user friendly," says Baker. "But it boils down to cost, value added, and market demand. Is there the market to justify it. We do commit a lot of resources to understanding what people really value — what will solve their needs to a degree to justify the cost."

From the spa manufacturers' standpoint, an attractive improvement in cartridge filters would be a lower cost. "Cost reduction can come in the form of improving technologies and processes," says Baker. "As with most any technology, the more streamlined and efficient the manufacturing process, the lower the cost."

Finley sees the possibility of multitasking filter fabrics ahead. "Future filter media has the potential for multi-functional removal of many things from the water," she says. "Spa manufacturers are asking for the highest filtration efficiency at the lowest installed cost."

More Per Square Inch

The biggest change in filter cartridges has been not in the nature of the filter media, but in the quantity of it that goes into the cartridge. "Not that long ago, it was common to see cartridges that were 25 square feet," says Collins. These days, 50 square feet is more common. "Typically, if you can increase that square footage of filtration area, you're going to have a better product. Filters may get taller, it may be that the diameter of the filter increases or a higher number of pleats. The more pleats you have, the more square footage. So those three variables will determine the overall square footage."

Because most OEMs work with a filter manufacturer to develop a filter for each particular spa model, the result is an eye-popping array of filter configurations. One supplier's replacement guide lists hundreds of different shapes and sizes of filters and has a sophisticated Web site with pages of cross references to help consumers — and reatilers — find the right replacement filter.

Is this a good thing in the eyes of the consumer? "I think the biggest turn-off for a consumer is walking into a store and the retailer not having stock on the shelf," says Collins.

Industry Standard

The solution might seem to be the adoption of a standardized filter size. For example, coffee filters come in just a few standard sizes. The Melita cone filters fit the KitchenAid coffee pot, and the Piggly-Wiggly brand basket filters work in the Mr. Coffee.

Fewer choices would be a good thing for the weary homeowner who can no longer get the correct filter for his five-year-old spa. "It is confusing for the consumer, because you get so many different stories," says Collins. "But every point of differentiation is something that helps make our company different from the competition. Companies feel that they can't differentiate in that category if everyone is using the same standard thing."

So while OEMs are not likely to give up their uniqueness anytime soon, many manufacturers try to make it as easy on the customer as possible. "We don't filter-hop. We have a 50-square-foot filter and that's our standard, and we have used that for four years," says Collins. "We try to help the dealer in terms of what they have to keep on their shelf. And there are a lot of good fulfillment companies that can help the dealer and the consumer."

Ultimately, the market dictates almost everything. "Now if there was a specific program that said, 'If you use this material, this configuration, this size — an industry standard — you're going to have better water.' Then it wouldn't be a competitive issue," says Collins. "I can't honestly see our industry deciding, 'OK, everybody, let's just all use the same standard cartridge filter.'"

Good Enough?

Even though the basic building blocks of spa filters — spunbond polyesters — have evolved to a remarkably efficient and functional state, manufacturers continue working to make innovations. "We're always looking at improving the product," says Baker. "Whether it's something that would allow the filter manufacturers to improve the cost of the filter, or a functional improvement that would help the user."