The Value of Heat in Extraction Cleaning


Since the mid to late 1960’s, when the very first portable hot water extraction machines for cleaning carpet were invented and introduced, arguments have raged about the value of heating the water that is used to extract the carpet. At that point in time, the conventional way to clean a carpet residentially or commercially was with a rotary floor machine utilizing carpet brushes and a shampoo formulation. Way back then, the “shampooers” railed against the perceived dangers of using hot water in the carpet cleaning process. If you look at the first extraction units that were produced, all of them had heating elements to heat up the water. Only later, either when the equipment manufacturer did not want to include the expense or added complexity of a water heating system, or when the cleaning solution water flow and pressure pumps that came out that outpaced the ability of an electric heater to keep up, did anyone even consider that a extraction unit might be made that did not try to produce hotter water.

Truckmounted extraction units, first introduced in the early to mid-1970’s took heating the water to an entirely new level, utilizing secondary heating sources to heat the water for higher solution water flow and pressure.

To this day though, there are still people who question, and even argue against the use of hot water in the carpet cleaning and extraction process. Everything from “it damages the carpet or backing” to concerns about the fact that the use of non-renewable power sources to heat the water is not a “green” or “environmentally friendly” concept. Our purpose here is to look beyond the rhetoric and make a careful evaluation and discussion that considers most of the benefits that hotter water brings to the carpet cleaning table, and carefully and respectfully address the criticisms that still exist.

Several independent and peer reviewed scientific studies have confirmed the value of heat in the carpet cleaning process. Yet this remains one area of carpet cleaning where gross misconceptions still exist. Hotter cleaning solution increases the chemical molecular activity of the cleaning chemical you are using (including water). This basic chemistry concept can be confirmed in basic science concepts by the Argonne National labs ( . Increased chemical activity means you will need to use less chemical to clean. Dr. Michael Berry, author of the book Protecting the Built Environment: Cleaning for Health, found that heat simply improves cleaning’s effectiveness. “Even without soap, small amounts of grease will dissolve in water, [but] the amount increases in hot water, sometimes ten-fold,” he says.

Hotter cleaning solution contributes to a healthier indoor environment.  Dr. Michael DSC_2095Berry and his associates, on behalf of the United States Environmental Protection Agency, did two groundbreaking studies measuring the impact of deep restorative carpet cleaning (utilizing hotter cleaning solution) in 1991 and 1994. The “Denver” Study in 1991 and the “Frank Porter Graham” Study in 1994 greatly advanced our understanding of the interaction between cleaning and the indoor environment. The “Denver” Study mainly looked at whether they could actually even measure particulates, gas phase organics, and biological contamination in carpeting before, during, and after carpet cleaning. The “Frank Porter Graham” Study was a collaborative effort that involved participants from the cleaning industry utilizing “best industry practices” and deep cleaning methods for on-going cleaning and maintenance in a Child Development Center on the campus of the University of North Carolina at Chapel Hill. Airborne dust contaminants were reduced by 52%. Total Volatile Organic Compounds decreased by 49%. Total bacterial was reduced by 40%, and total fungi declined by 61%

The results of a 2010-2014 study conducted by Airmid Healthgroup, a leading research organization, talked about the measured effective of using hot water in extraction cleaning.  As to the use of steam or water-based cleaning systems, the researchers suggest carpet extraction—and more specifically hot-water carpet extraction—is necessary to thoroughly clean carpets and remove deeply embedded soils and contaminants, helping to prevent them from becoming airborne.  According to the researchers, “results show that the proprietary hot water extraction cleaning process was highly effective in reducing allergen levels in carpets and soft furnishings. Surface levels of dust mite allergens on carpets, for example, were reduced by 91 percent, of cat allergen by 95 percent, and of dog allergen by 97 percent. The cleaning process also resulted in a marked reduction in airborne cat allergen exposure. The process also effectively reduced exposure to airborne mold.”

Hotter cleaning solution also contributes to faster evaporation of residual moisture resulting in faster drying of the carpets and reducing “downtime.”

Hundreds of portable and self-contained extractors have achieved a Bronze or Silver rating in the Carpet and Rug Institute Seal of Approval extractor testing program. Is it a coincidence that virtually every Gold rated portable carpet extractor in the Carpet and Rug Institute Seal of Approval Program is equipped with a heating system? Hotter cleaning solution results in increased overall cleaning effectiveness.

The simplest way to understand this question is ask yourself if you would wash dishes in cold water. Anyone can see that the heat helps melt away all the stuff left on dishes. The hot water helps kill any bacteria. And the dish detergent works better in hot water. This means the dishes come out cleaner and healthier and you don’t have to work so hard. In fact, if you have worked in in the kitchen area of a restaurant, you know that health department regulations often require that the temperature of the water in the dishwasher always remain above 130◦F. Why?  Because the sanitizing effects of hotter cleaning solution temperature has long been recognized. It only makes sense the same effect would take place in carpeting that is generally constructed of a synthetic plastic material.

There are a couple of occasions where the conscientious cleaning technician should consider reducing their cleaning solution temperature, particularly if they are employing a truckmounted extractor. It is generally recognized that wool carpeting should not be cleaned with solution temperatures above 160◦F. On some inexpensive plush cut pile carpets that are subject to “streaking” from the wand jets, decreasing the temperature of the cleaning solution is advised.

As far as the criticism that heating up the water uses limited resources, there are several arguments against this concept. Using only cold water, particularly on carpets that have been exposed to a higher level of oil and “sticky” based soiling, will increase the amount of time it takes to clean the carpet. It will require multiple passes of the cleaning wand across the carpet, increasing the likelihood of over-wetting the carpet and extending drying times. It could be mandated that restaurants use cold water in their dishwashers also, but my guess is that health department regulators would tell you the resources used to heat the water are worth the added protection to public health. In the case of portable extractors, the use of electricity to heat the water does use additional resources through the consumption of electricity. Dr. Berry counters this argument in his written response to proposed New York state guidelines for cleaning, “I suggest it is for more important to heat and use water in the pursuit of health protection than it is to reduce energy use and to increase water conservation.” One of the points that I brought up with Green Seal® that seems to get completely overlooked by organizations writing policy that affect our industry has to do with the way that most modern truckmounts work. The fuel consumption used to power a truckmounted carpet cleaning machine, whether it be a slide-in or direct drive unit is going to exist in order to operate that unit. In most cases,  it runs on gasoline. The heating of the water in a heat exchanger truckmount works by capturing heat from other sources (engine, blower, radiator, etc…) that are being powered anyway. The hot water created by a truckmount does not require the use of any additional resources beyond those required to run the truckmount. Using the fuel source for dual benefits – what could be greener than that?

Virtually all carpet manufacturers recommend or require hot water extraction cleaning in their own maintenance literature.  – Hot water extraction; not warm or cold water extraction. The companies who make carpet, after doing a little research of their own in the late 1980’s removed any warnings about hot water in carpet cleaning when they determined it did not damage the carpet, or the chemical treatments applied to the carpet.

In the end, when weighing the facts and the measured data, the only reasonable conclusion that one can reach is that heat makes a huge, vitally important and even “green” contribution the effectiveness of the carpet cleaning process.

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