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  • Joe Clark

Everything You Need to Know About Carpet Cleaning Methods

To industry outsiders, carpet cleaning might sound like a straightforward process, but as cleaning professionals, we know that nothing is ever as easy as it sounds. There are multiple ways to approach almost any cleaning task, and carpet cleaning is no exception to the rule.

As a cleaning professional, your clients are likely to ask you all kinds of questions about tasks that may fall outside your usual service scope, and they’ll expect a recommendation of some sort. In this article, you’ll find out about the pros and cons of various carpet cleaning methods; when to use them or recommend them; and what can be expected of them.

Hot Water Extraction (HWE) Carpet Cleaning

Most people refer to this as “steam cleaning,” but that term refers to an altogether different industrial process. Real steam would be way too hot for most carpet fibers and could damage the carpet very badly. Just as a wool sweater or velvety fabric can shrink or get fuzzy in the wash, so steam can hurt carpets with these materials and textures. Also, artificial fibers could simply melt because the steam is too hot for them.

Thus, so-called steam cleaning of carpets is really hot water extraction cleaning. The machines that we use for hot water extraction cleaning spray heated water onto the carpet while simultaneously sucking it up. In the process, the dirt in the carpet gets dislodged and sucked away.

Adding cleaning chemicals to the equation can produce better results, but once again, you must take the type of carpet fiber into account when selecting chemical agents.

Truck-Mounted vs. Portable

Equipment ranges from the baby machines that homeowners can rent to big, truck-mounted machines. The latter are far more effective and have a unique set of pros and cons.

  • The long hose that goes from the truck to the operator means that you must leave doors or windows open. It also presents a tripping hazard.

  • Hoses could be too short to reach, especially in large buildings or high-rises.

  • Because the machinery is mounted on a truck outside the building, there’s less noise indoors.

  • Unfortunately, the sound of the truck idling in the driveway or at the roadside can upset neighbors, and in certain areas, it would be against municipal by-laws.

  • On the plus side of the equation, truck mounted equipment is more efficient, both in terms of results and time needed for the cleaning process, and the extra suction power helps carpets to dry out faster.

  • Carpet manufacturers prefer hot water extraction cleaning because the deep down dirt removal prevents particulate abrasion that causes wear.


Preconditioning helps to loosen up stubborn dirt. The choice of preconditioning agent depends on the carpet’s fabric. Use alkaline solutions when working with synthetic fiber carpets. Choose a mildly acidic solution like diluted acetic acid on woolen carpets. Now, you can use a scrubbing machine to work the preconditioning agents into the carpet. Finally, the hot water extraction tool rinses out the preconditioner together with all the embedded dirt.

Woolen carpets may need a final step if the detergent you’re using has a high pH. This can make the carpet texture hard and scratchy, but the problem is easily solved with an acetic acid solution similar to the one you used to precondition.

Extraction and Drying

HWE cleaning uses a whole lot of water and will leave the carpet damp no matter how strong the suction power of your equipment is. The final drying process is important because you need to prevent mold growth and you don’t want permanent brown water marks on natural wool carpets. That means good air circulation, and sometimes, we need to use fans or dehumidifiers.

Extraction and drying processes go hand in hand, and it takes experience and good equipment to find the right balance. You do want to get as much dirt as possible out of the carpet, which means a relatively high flow rate, but you do need to get that carpet dry pretty quickly which might mean using a lower flow rate, particularly for thicker carpets.

Vacuum Wash as a Basic Alternative

Vacuum wash systems will work on all surfaces including carpets. A wash-head sprays the water onto the surface, and it is almost immediately sucked back up. This is a relatively basic cleaning system and won’t handle heavily soiled carpets, but it is fine for light cleaning, doesn’t abrade the pile and doesn’t leave the carpet as wet.

Dry Cleaning Methods

To limit the problem of damp carpets, various cleaning methods have been developed. Some of them aren’t strictly speaking 100% dry. We could say that they are “drier” instead. Professional carpet cleaners would choose one of the following options.

Very Low Moisture (VLM) Systems

These relatively new systems combine dry compounds and purpose-designed cleaning solutions. From a professional perspective, these systems save a lot of the drying headaches, and they also get the job done faster. However, they’re less effective than hot water extraction, which means that cleaning teams have to apply special treatments to dirt spots and high traffic areas.

Special emulsifying agents sprayed onto these areas loosen the dirt. These pre-treatment compounds shouldn’t remain on the carpet for more than about 15 minutes as a rule of thumb.

Dry Compound Cleaning

The compound isn’t altogether dry, but it dissolves and attracts grime. After it has been thoroughly worked into the carpet, it is left to dry before being sucked away with an industrial vacuum cleaner. Although this system might sound very easy, it has its own set of complications to deal with.

Firstly, the compound has to be worked into the carpet, and a machine does a far better job of this than hand brushing ever could. But the need for the brushing machine and the carpet wear it inevitably causes aren’t the only problems. The dry compound itself is very difficult to remove altogether, and it has been linked to allergies. Some residues can even cause the carpet to become discolored.


Encapsulation uses detergent polymer chemistry to bind dirt to their molecules forming tiny crystals. Early attempts at encapsulation formulations were problematic, with carpets becoming rapidly re-soiled after cleaning because any residues left behind would continue to attract dirt.

Newer formulations are much more effective. Professional carpet cleaners apply encapsulation products using specialized applicators or a compression sprayer. After the 20 to 30 cm that are required for the detergent to dry, a vacuum which usually forms part of the cleaning system sucks up the polymer and dirt crystals. Although these attach themselves to carpet fibers, the bond is very weak, and the residue breaks away from the fibers easily.

Bonnet Cleaning

Using this type of system requires considerable skill. First, the operator applies a mist of detergent to the bonnet. Now, the bonnet, a type of round buffer pad, picks up the dirt. Operators must master several tricks.

Firstly, they must ensure that there is enough detergent to keep the bonnet lubricated or it will damage the pile. If it is too wet, it leaves residues behind causing the carpet to get dirty again much faster. The operator must also replace the bonnet often enough because once it is saturated with grime, it stops attracting new dirt.

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