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Cleaning carpets: hot water versus cold water

While hot water cleaning may use more energy, its benefits may outweigh its drawbacks
Thursday, January 16, 2014
By Mark Cuddy

The professional carpet cleaning industry – in fact, the carpet industry in general – has had its share of scuffles in the past two or three decades. At one time, a good 25 years ago, some health officials believed that carpets in schools were the cause of an increase in childhood asthma attacks and other respiratory problems.

Soon, schools in Sweden and parts of North America were removing carpeting, believing that as soils built up in the carpet, it negatively impacted Indoor Air Quality (IAQ).

However, further research, as many cleaning professionals and carpet cleaning technicians now know, revealed that carpeting actually absorbs soils, including the airborne soils that can trigger asthma and other respiratory problems. Instead of being the culprit, carpet was actually helping to solve the problem.

Then, approximately 15 years ago, there arose a widely-accepted belief that carpeting required more time and attention to maintain when compared to hard-surface flooring. While the results can vary, studies by the Carpet and Rug Institute (CRI) once again found just the opposite.

“Carpet … can be 65 per cent less expensive to maintain than hard surface flooring,” the study reported. “While buying and installing hard surface flooring appears less expensive than carpet in the short-run, the true cost of labour, supplies and equipment over an average 22-year lifespan makes carpet a more cost-effective [flooring] choice.”

Now the carpet cleaning industry is grappling with another issue. In 2005, as part of a green cleaning initiative, New York Public Schools instructed all custodial crews to use only cold water when performing cleaning tasks … including carpet cleaning. As was expected at the time, other school districts “greening” their school maintenance operations adopted the same cold-water restrictions.

However, will this initiative prove to be a mistake? Let’s look a little bit deeper into the facts about hot-water cleaning and you can decide for yourself.

Heat Fundamentals

Recently, when a couple were selecting a new automatic dishwasher, one of the features the salesperson discussed was the fact that one model could heat the water to a higher temperature than its nearest competitor. The benefit of this, according to the salesperson, was that heat helps dissolve grease and soil on pots, pans and dishes, and that most of the dishwashing detergents now available are designed to work with hot water—in fact, the hotter the better.

This is certainly not news. Back in the late 1800s, a Swedish physicist and chemist named Svante A. Arrhenius, researching the connection between heat and energy, made an important finding that would impact cleaning forever.

He discovered that for every 10-degree Celsius (18-degree Fahrenheit) increase in temperature over 48-degrees Celsius (118- degrees Fahrenheit), the amount of energy released is doubled. As it applies to cleaning and, more specifically carpet cleaning, this means that for every 10-degree Celsius over 48 degrees Celsius, the effectiveness of the cleaning process doubles.

Known as the Arrhenius equation, this finding admittedly is not unanimously accepted by scientists. However, as far as we know, none of the doubters claim cleaning in cold water actually improves cleaning.

In fact, using the dishwashing example, we could ask how many non-believers prefer to wash their own dishes in cold water. A simple test cleaning two greasy pots, one with cold water and the other using hot water, will most likely show that the hot water helps melt away the grease, making the cleaning of the pot considerably easier.

The same can apply to carpet cleaning. According to William R. Griffin, a well known cleaning consultant, higher temperatures “assist in the cleaning process by helping break down oily residues … in carpet fibres. [Further] most detergents are formulated to work more efficiently at higher temperatures.”

According to Griffin, other potential benefits of using hot water go beyond just cleaner carpets, as important as this is. He also suggests that carpet fibres tend to regain their original “loft and resilience” when a hot-water carpet extractor is used to clean the carpets. Of course, the ultimate goal of all cleaning, including carpet cleaning, is to help protect human health. But, along with this, restoring a surface – such as carpet – to its “like new” appearance is of great importance to many customers.

Could Heat be Green?

 As mentioned earlier, we know that one of the underlying functions of carpeting is that it collects and holds soils, preventing them from becoming airborne and marring IAQ. However, these contaminants must be removed periodically in order for the carpet to continue providing this service. Along with regular vacuuming and spot cleaning, these soils are best eliminated through deep cleaning or carpet extraction, and most effectively using heat.

“The deep cleaning process using hotwater extraction pulls out deeply-embedded soils and sticky residues that have not been removed with vacuuming or interim cleaning,” Griffin said. “Most experts agree, hot-water extraction does the most complete job of removing all soils.”

If carpets are more effectively cleaned using hot water, helping to protect IAQ, then one of the goals of green cleaning—protecting human health—has been accomplished.

In addition, according to the Arrhenius equation, the cleaning effectiveness of chemicals actually improves as temperatures go up, and that often means less chemical (and water) is necessary to clean the carpets. Whenever less chemical is used in cleaning, cleaning’s impact on the environment.

You Decide

Earlier I suggested that I would let you decide if using cold water to clean carpets was better for the environment. However, in all fairness, we have not mentioned why some green cleaning advocates believe cold water is preferable. Very often it comes down to two things:

Fumes: Chemicals tend to release fumes when mixed with hot water, which can potentially be harmful to the user and the environment.

Energy: Hot water extractors tend to use more energy than cold-water systems, potentially making them a less sustainable cleaning method.

As to the fumes, most cleaning professionals and carpet cleaning technicians already mix carpet cleaning chemicals with cold water. This helps eliminate or minimize the amount of fumes released in the mixing process.

It is true that these hot water machines typically use more energy. However, as with so many things, we must always weigh the benefits with the potential drawbacks. If hot water results in less chemical and water being used, and carpets are more effectively cleaned and dry faster, helping to protect the indoor environment, the benefits just may outweigh the drawbacks. You decide.


Mark Cuddy is national sales manager for U.S. Products, which markets U.S. Products High Performance Carpet and Hard Surface Extractors through Nilfisk-Advance throughout Canada.

7 thoughts on “Cleaning carpets: hot water versus cold water

  1. I found the content as good when I went through your article. This is very important to use hot water to remove soils residue from the carpet as it contained,which carries literally asthma. So i’m agree to use of hot water rather than cold. Thanks for sharing this amazing post.

  2. I have to say I agree with a lot what has been said here and here is my take on things.

    When you clean anything yourself. Not in a professional manner. But just something in the kitchen. Do you soak in hot water or cold water? We know what the answer is. It’s hot water. It’s more effective at softening up all the grime and gunk so it can be cleaned. It’s not different to you carpets. Think about a washing machine also. Sure, some things are washed on a cold cycle but for the most part hot water is used.

    I just like to keep things simple.

    Those are just my thoughts. I’m an avid reader of your blog but this time I thought I’d chime in.


  3. The big question is, how hot is hot? The water heater normally heats the water to about 135 degrees Fahrenheit. Is that hot enough, or is it necessary to turn the hot water heater up to max?

  4. The points you made about using hot water when cleaning carpets really caught my interest. We’ve been meaning to improve the design of our living room by adding some more decorations to it, and carpets were the first thing I had in mind. However, since these usually end up causing a lot of allergic reactions when dirty, I would definitely push for hot water when cleaning them. With that in mind, I’ll look for any professional cleaning services that can freshen up the old carpets we have before using them and cleaning them ourselves.

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