There are numerous advantages to using cold water for cleaning: it saves energy (and therefore money), offers commercial benefits when it comes to being perceived as “green”, prevents wear-and-tear on the fabrics, and it gets rid of dirt just as well as hot water. However, there is one aspect in which hot water is supposedly better than cold water: killing germs. However, a deeper look finds that the evidence for this assumption is lacking.
On the surface, the claim makes sense: after all, in the days before effective filtration and water treatment, boiling water was the best way to kill dangerous bacteria. But that refers to boiling water; when we refer to hot water, it may be hot but it is still a long way off from boiling. Most homes will not heat water to 70⁰C (160⁰ F), which is the temperature the Centers for Disease Control (CDC) recommends for killing germs, anyway. Furthermore, even if the water begins at that temperature, it won’t stay that hot as it contacts the surface that is being cleaned.
Most of the people who advocate for hot water are quoted as “experts”, but after extensive Googling sessions we were unable to find the original studies cited by the Daily Mail and/or the other news outlets supporting the idea that using cold water is less hygienic. The studies that we could find show that the peroxy acids that are generated by activating agents such as Britebleach NOBS are sufficient to kill off most bacteria. An independent assessment confirms that the combination of NOBS, sodium percarbonate, and detergent can eliminate bacteria even at relatively low concentrations in room temperature water. While fungi and mold spores are somewhat more difficult to kill, higher concentrations of NOBS and sodium percarbonate can eliminate viable spores as well. The transfer of germs to clean things appears to happen from dirty machines, rather than from dirty laundry, as laundry-laundry contamination in a washer does not appear to be an issue.
Most of the studies that have been done on this subject are single, small studies, but they all conclude that, thanks to modern detergents, washing in cold water is no less hygienic than washing in hot water. Seeing as how laundry accounts for almost 25% of water use in an average home, the savings – both in terms of money and the environment – from switching to cold water go a long way towards curbing our carbon footprint. The evidence shows that the idea that hot water is better for cleaning is nothing but hot air.
The Sirius effect:
Progress isn’t always a single monumental thing or event. Sometimes it’s a little thing like convincing someone to turn down the temperature of their laundry. At Sirius, we may not have all of the solutions, but we can make it easier to begin the small changes that help make the world a better place. All of the chemicals we carry have this in common. Want to know if you can make the switch? Contact us and find out how hot it is to clean cold.