Close-up of Reemay cartridge filter fabric
Reemay Close-up of Reemay cartridge filter fabric

When it comes to easy maintenance and water conservation, many consider the cartridge filter to be king.

However, cleaning should be handled with care: Unlike their sand or DE counterparts, cartridge filters cannot be backwashed. Therefore cleaning is a manual process.

Here, we’ll explore how to ensure that these pleated particle-picker-uppers filter with optimal efficiency.

Filtration 101

To understand how to keep filtration elements working properly, it helps to know how they work.

Most cartridges are comprised of a non-woven, spun-bonded polyester fabric. Under a high-powered microscope, you’ll see the individual fibers intersect, creating a tight mesh through which water flows and dirt is trapped. This webbed structure can sieve particles between 10 and 12 microns, manufacturers say. Its pleated depths maintain hold of the gunk. Over time, those folds harbor more and more crud, reducing their ability to filter particulate and driving up pressure on the pump. At some point, the cartridge will reach maximum capacity and call for a cleaning.

This all means that, because of a typical cartridge filter’s makeup, job No. 1 is to clean the product in such a way that the fabric does not become compromised from clogging or a change in the fabric’s weave.

How not to clean

As part of the winter closing process, some professionals offer to take their customers’ cartridges off-site for a thorough washing so they’re good as new come summer. It’s a helpful service, but only when performed correctly. Some technicians dish out all sorts of damage while doing this.

Pressure washing is a common mistake. Though sturdy, the cross sections of the fibers, which are commonly heat bonded, can break under high pressure, rendering the element useless. That’s why a garden hose is recommended over mechanical agitation.

But, of course, water alone sometimes doesn’t cut it. That’s why many techs employ a multi-step process comprising a detergent wash, acid bath and an enzyme treatment in an effort to rid the cartridge of stubborn organic matter, oily buildup and scale.

Be careful about the order in which you do this. Step 1 is not — we repeat, not — an acid wash.

Here’s why: Polyester has a tendency to absorb oil. That’s a good thing, because you don’t want sunscreen creating an oil slick on the surface of the pool or scum lines on the tile. When it’s caught in the filter, however, it forms a transparent sheath over the trapped debris. On its own, this does not cause a problem. However, performing a strong acid wash as a first step will turn it into a problem by opening the pores in the fabric and driving oils and dirt deeper into the material, say Pleatco


Plus, a heavy-duty acid wash can be deceptive. Though the filter might come out looking as white as the day it was installed, it could be that you only succeeded in bleaching the debris. On top of that, the particulate and debris now are forever trapped in the fabric. The result? The filter is too tight, causing the pressure to spike within days of cleaning.

Acid also deteriorates the glue that binds those thin bands of polyester to the pleats. Those support bands, typically included on cartridges 12 inches and taller, are crucial to maintaining the integrity of the pleats. “It will eat at the glue and those bands will fall apart,” warns Joe Marcotte, vice president of sales and marketing with Filbur Manufacturing in La Palma, Calif.

That’s why he recommends foregoing acid altogether. Instead, techs should consider a pH-neutral formula designed to combat calcium.

When it comes to degreasing and enzyme treatments, follow the directions carefully, then thoroughly rinse between the pleats. They make special hose nozzles for that specific purpose.

Question of compatibility

Because different treatment products may interact differently with the cartridge fabric, combining the two should be done with caution. Here are tips for working with pools that incorporate the following products.

• Clarifiers and flocculants

These products are wonder-workers, able to turn a cloudy pool crystal clear within a day or two. By introducing a positively charged substance into the water, it attracts negatively charged particles, forming a molecule chain large enough to sift out.

But not all clarifiers are cartridge friendly. Synthetic clarifiers have a tendency to gum up the works. As previously mentioned, polyester absorbs oils, so it’s not in your best interest to put more petroleum-based polymers into the pool.

“The problem is you’re using a petroleum to gather dirt, so you’re forming a gunk that sticks to the filter material, causing a clog,” says Terry Arko, recreational water specialist with SeaKlear, a chemical manufacturer in Norwalk, Conn.

That’s why cartridge makers recommend using a biodegradable clarifier for this task. The active ingredient in some nonpetroleum products is chitosan. Derived from crustacean shells, it forms a loose-net molecule chain that encapsulates oils, preventing them from absorbing into the filter fabric.

Another option for a speedy recovery is to use a filter aid. Some manufacturers say it’s fine to toss a little DE into the filter, others advise against it. In some instances, it may even void the warranty. So check with your supplier first.

One product that some techs swear by is cellulose fiber. This forms an artificial cake around the cartridge, helping it catch dead algae — which, at 4 microns, can slip past the pores of an untreated cartridge. And it’s an easy rinse.

• Phosphate removers

Here’s another miracle product, but one that should be used carefully. When it comes to residential cartridge filters, not all phosphate removers are alike; commercial-strength versions can be overkill.

Pleatco engineers have seen a heavy-duty version of the product form a gel deep within the pleats. It’s best to stick with the home-grade stuff.

Whether the pool is treated with phosphate removers, clarifiers or flocculants, service pros should rinse the cartridge within 24- to 48 hours for best results. “That’s been a saving grace for our customers,” says Abhi Pillai, Pleatco’s director of engineering and research.

• Biguanides

Biguanide-based products serve as an alternative to traditional sanitizing methods, namely chlorine. Originally devised as a sugar-based disinfectant, biguanide is the only non-halogen sanitizer approved by the EPA. It’s said to work well enough for pools with sand filters, but the product’s chemical composition isn’t compatible with cartridges. It gets caught up in the fiber webbing, forming a viscous layer that sticks around even after scrubbing.

“That snot is damn near impossible to clean out of a filter,” said Tim Ruesch, key account manager for pools and spas at Berry Plastics, a producer of non-woven fabrics such as Reemay’s.

Keep a spare

Smart techs have an inventory of sacrificial cartridges at their disposal. These come in handy when doing an acid-based startup, stripping out heavy iron and calcium, or a super chlorination treatment. Let a used cartridge take the brunt of the abuse.

The bottomline: None of the tips above suggest that the cartridge is delicate. Far from it. It’s truly a solid performer boasting a long service life. That’s why it’s been a mainstay of the industry for decades.

But like any filter, a little TLC goes a long way.