loaded, regenerative media filters regenerate by bumping, a process in which no water is lost.
Perlite is added to the filter through a slurry funnel. Then pool water is added into the tank and the perlite and water move toward outlet tubes, covered with polyester fabric, which becomes coated with the perlite medium, referred to as the precoat cycle. Water exiting from the perlitecoated filter is then clear, and filtration has begun.
Dirt particles collected by the perlite causes the pressure of the circulation pump to rise. This causes a bumping cycle to begin, where the outlet tubes covered with the perlite to shake the perlite off, which remixes the perlite back into the chamber before they re-adhere to the tubes with differently arranged perlite, which, though dirty, is still highly effective at filtering tiny particles.
After numerous cycles of filtering, bumping, and pre-coating, eventually a point is reached where even after a bumping cycle the pressure required to push more water through the filter is too great. At this point, it becomes necessary to dump out the entire slurry of water and dirty perlite in the tank, replace it with new, and the cycle begins again.
Among the greatest advantage of regenerative media filters is their filtration capability. Water filtered by regenerative media filters is truly crystal clear. Further, because they are capable of filtering exceptionally fine particles, users frequently report lower chemical use.
The other great advantage is in water savings, which is a big bonus, particularly in drought-prone regions. Backwashing the filter is not a part of routine maintenance. Rather, once the filter pressure becomes too great, and it is time to replace the perlite, only the volume of water of the filter tank is dumped. That water loss is much less than what is lost in backwashing, or in hosing a cartridge.
Commonly reported disadvantages include the upfront sticker price, which is certainly higher than traditional sand filters.
Secondly, they also require routine perlite replacements after several cycles of use. Compared to sand, which can last for years, some may find this a disadvantage.
Finally, they aren’t a great fit with high oil content. With highly used outdoor commercial pools, where the water sees a lot of sunscreen, regenerative media filters may not be the best option. Oils and lotions tend to cake the perlite, which will result in more frequent dumping cycles.
Cartridge filters offer numerous advantages over sand and DE in that they are easy to maintain, ecofriendly in that they are water savers, and are easily replaced once they have reached their end of their useful life.
But not all cartridges are created equally, and knowing a bit about the components of a cartridge filter may help facilitate understanding which cartridges have superior filtration ability, durability, and provide greater energy savings.
The main components of a filter cartridge are the core, the filtration medium (fabric), the end caps, and the bands that hold them together.
Many manufacturers use a standard core, made of PVC pipe, with holes drilled through to allow water to flow through the core and fabric before returning filtered water to the pool. The core serves a couple of functions. First and foremost, it provides a scaffolding for the filtration fabric. Depending on the material of which it is composed, greater or lesser lifespans can be achieved. Depending on how open the core is, greater or lesser flow can be realized. Greater flow accomplishes three things. Greater flow means more filtration capacity. It also creates less wear on the circulation pump, and is associated with lower energy costs.
The filtration medium is the essence of the filter. Most standard filters use a Reemay tri-lobal filtration medium. The product is constructed of continuous, tri-lobal spun-bond fibers made of 100-percent polyester. It is made without acrylics, binders, or glue that can weaken and dissolve during use or cleaning. This process produces a rigid fabric that readily accepts and holds sharp pleats, providing excellent column strength. Further, the tri-lobal shape of the fibers maximizes the filtration surface area, and the continuous filament construction results in unsurpassed cleanability and durability.
Advances in filtration have led to “point bonded” filtration fabric. It is made with uniformly spaced weld spots, making it strong and capable of returning to a high degree of original performance after it is cleaned. It has more fibers per area, allowing for greater dirt-holding capacity.
Pleating is extremely important in the fabric because it creates the peaks and troughs that catch the dirt. These pleats need to be sharp and precise for optimal flow and filtration capacity. All cartridge filters are pleated to a specific pleat count, and most are held together and around the core by three or four bands to keep the pleats even. These bands can break or stretch, which can allow the pleats to fall apart.
Advances in technology have resulted in some bandless cartridges, which hold the pleats in place on the inside at the core.
End caps hold the cartridge together and also act as a seal in the filtration caps on pool filters. Cheap end caps crack under pressure and result in a shortened lifespan. Tip: look for a company brand name and part number for quality filters.
DE Filters provide excellent filtration quality, filtering particulates in water from 3-5 microns, and are ubiquitous in residential application, but in spite of this, they are not universally loved, especially by pool service technicians.
The DE itself, composed of crystalline silicone dioxide, has been linked to health problems for users. It can be harmful to sensitive ecosystems. It’s messy to use. It doesn’t break down, and because it results in bridging between grids, doesn’t completely backwash and can be difficult to rinse away.
For these reasons and more, some service professionals prefer DE alternatives. Today, the popular choices are perlite and cellulose.
Perlite is a natural product, produced by heating volcanic rock to extremely high temperatures, at which point it explodes and expands greatly, like popcorn.
It does this because upon heating, water trapped in the structure of the material vaporizes and escapes, and this causes the expansion of the material to 7–16 times its original volume. The expanded material is a brilliant white, due to the reflectivity of the trapped bubbles.
These perlite kernels are then ground down into a very lightweight powder for use in DE water filters as well regenerative media filters. Because perlite is so low density, generally only half the amount of powder is needed, compared to DE.
Proponents of perlite say that the light weight results in less bridging between grids, more complete backwashes, and longer filter cycles, as compared to DE.
Perlite is twice the cost of DE, but because half the weight is needed, you pay the same for the same filtration ability of 3-5 microns.
Cellulose fiber filter media is made of plant-based fibers – generally wood pulp.
It is natural, biodegradable, renewable, and non-toxic.
Cellulose fiber can be used as a replacement for DE, and it also makes a good filter aid for sand and cartridge filters, increasing their filtration ability and protecting filter cartridges.
Because cellulose can also trap oils, grease, and particles as small as 2 microns, unlike DE, it may clog up sooner.
Cellulose fibers can even clog up from the use of polymer chemicals, such as algicides, clarifiers, phosphate removers, or metal removers. These chemicals are not recommended for use with cellulose media.
Cellulose is the costliest of DE filter alternative – but it goes much further, only 6 ounces or .375 pounds is needed for each 10 square feet of filter area.
To purchase CelePerl visit www.epminerals.com/products/celaperl
To purchase The Filter Fiber Stuff, visit www.jacksmagic.com/product/the-filter-fiber-stuff/