Talkin' 'Bout Regeneration

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The idea of regenerative filtration is almost as old as The Who’s famous song from which this article gets its title, but the concept of extending filter life to avoid cleanings (and the water they require) has drawn new interest as drought headlines become more prominent.

Regenerative filtration has been growing among large commercial systems for some time; they are commonly seen at waterparks and community recreational facilities, as they provide finer filtration than sand filters while allowing longer maintenance cycles. They are much smaller than sand filters, which saves space in the equipment room, but the biggest selling point over sand filtration is the huge water savings and the chemicals and heat contained therein.

That is to say, for every gallon of water lost in a sand filter backwash, there is a commensurate loss of chlorine, ancillary chemicals and heat. A 1000-gallon backwash in a pool heated to 72-degrees wastes 136,000 BTU. And of course, high-rate sand filters in a large facility can backwash tens of thousands of gallons a day.

Heat energy and chemical conservation used to be the main interest, but now, as anyone who reads the news can attest, wasted water is the focus. Pools of all sizes are under pressure to cut waste and prove they are prudent with their supply of H2O, lest that supply be curtailed or cut off.

An efficiency measure such as a filter that conserves water and energy, goes down well with CEOs and governing boards these days, and for that reason, regenerative filtration is gaining new adherents and customers on the commercial side, according to Jack Stanley, regional sales manager for Neptune-Benson.

The residential market, on the other hand, has always seemed an impractical home for regenerative filters due to the expense. The typical owner of a 20,000-gallon backyard pool will not be interested in the added dollars for a regenerative filter when a cartridge, sand or D.E. filter can provide good service for a fraction of the price.

But times are changing. At the high end of the backyard market, customers with expansive, unfettered budgets may be attracted by the green credentials offered by a regen filter. And if the current drought continues or grows more severe, the extra dollars for a filter that saves water may start to seem worth it for some mid-range homeowners.

How It Works

The heart of any technology is always a very simple physical law or phenomenon.

The basis for regenerative filtration is the fact that when you shift and resettle a filter medium particle such as D.E. or perlite, you expose clean, unused facets which can then be used to filter more dirty water.

That’s where the name comes from; when you shift the particle, you “regenerate” its ability to collect dirt. For a while, that is. Eventually the particles become surfeit with pool gunk and must be replaced like any other filter medium.

In an ordinary backyard D.E. filter, the D.E. sits on the filter grids, grabs waste and debris from passing water for a while, collects as much as it can in that position and orientation, and then is rinsed away when the service tech comes to do a cleaning.

If the particles are shifted and reoriented on the grid, they can collect more dirt. Residential service techs sometimes use this trick if they’re pressed for time and can’t do a full cleaning. They “stir” the D.E. around, providing that same reorientation of particles to allow them to continue to filter debris a while longer.

Commercial regen filters just do that mechanically and more effectively. They isolate and flood the filter chamber, which lifts the filter medium particle and repositions it in another place and orientation, exposing new clean facets, ready for more filtration. This extends the period of time between cleanings (just as it does in the harried service tech’s backyard) and therefore reduces total cleanings and saves water.

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