How well does the PureWash Pro (ozone) kill germs in the laundry?

My PureWash Pro experiments have moved to my new experiments website. You can read them here.

The pureWash Pro is a very exciting product that is supposed to kill the germs in the laundry. It is a machine that hooks up to your washing machine and is pretty easy to install. Basically, the water from the wall goes through the pureWash and then into your washer. The pureWash infuses the water with ozone which is supposed to kill germs. This is very exciting because I would love something besides chlorine bleach to effectively kill germs in the laundry. I've done a ton of laundry experiments and you can see all of those results here

The pureWAsh website claims that the pureWash kills 99.9% of bacteria and mold. The company has scientific studies done by EMSL Analytical, Inc. showing that PureWAsh Pro eliminated 99.96% of Staph aureus bacteria in an experiment where they applied the bacteria to cloth, washed it in a washing machine using the pure wash, and then measured how much was bacteria left in the cloth. Their scientific studies also showed that the PureWash Pro eliminated 99.56% of Pseudomonas aeruginosa, and 86.18% of Legionella anisa. I have read all the scientific reports on this testing. 

In addition to killing germs, you don't have to use detergent with the pureWash. This saves you money gets rid of build up and skin irritation caused by detergent. It is also environmentally friendly because you are not supposed to use hot water with the PureWash. The ozone doesn't stay dissolved in the hot water. 

The pureWash Pro company sent me the PureWash Pro to test. They did not pay me at all. I just got the PureWash for free to test. As always, I report my experimental results which may or may not be what a company wants to hear. 

About the Scientist

If you are new to my website, let me tell you a little about myself. My name is Annie Pryor. I have a Ph.D. in biochemistry from The Ohio State University. After a few years working in a research lab, I "retired" to be a stay-at-home mom. When my first baby got a terrible stomach virus that required a trip to the ER, I decided to research the subject and created this website dedicated to reducing the prevalence of the stomach "flu" in the world. My 3 little kids keep me busy, but I still get a hankering to do experiments now and then. I've tested cleaning productshand sanitizersproduce washing techniques, essential oilsNorwex ClothsSteriPenslaundrylunch box coldness, the Phone Soapand even sunlight. I also happen to be the inventor of a really useful drying rack. I invented it because I needed a convenient place next to the kitchen sink to hang baby bibs up to dry between meals. It is also perfect for drying sports water bottles, dish cloths, food-storage bags, cleaning cloths and many other items. I have a shorter drying rack (12.5 inches tall) and a taller 15 inch rack. The Mommy Genius®  Drying Racks are manufactured in the USA and is available on Amazon. If you would like to be informed when new experimental results are posted, please like my Facebook page

I am also very proud of my daughter, Katie Scarlett. At age 8, she has written, illustrated, and published the first 3 books in a delightful series! Princess Katie and the Fairy Tea Party , Princess Katie and the Mermaid Lagoon and Princess Katie and the Kitty Club are available on amazon. The stories are so sweet and teach about kindness, forgiveness, including others, and doing the right thing. I think every little girl would love them! Please consider buying them for a little girl that you love. Katie gets about a $2 royalty from amazon for each book sold that is getting deposited into her college savings account. 


I tested the PureWash Pro on 3 different loads of laundry. Here is a picture of my dish towel load. 

First, I blotted several pieces of dirty laundry onto an agar plate. This would be the dirty "before" plate. If the laundry was dry, I wet it with tap water. The cloth needs to be wet or damp for the best transfer of germs to the agar plate. 

Then I washed the load in my Whirlpool duet HE front loader. I used the cold wash cycle set to extra heavy soil level. The cycle was 58 minutes. You have to use cold water only with the PureWashPro because the ozone is dissolved in the water. It doesn't stay dissolved in warm or hot water. 

The PureWash was hooked up and turned on automatically when the washer started. A blue light comes on in the display window, and you can see bubbles in the window as extra oxygen is being added to the water. 

When the load was finished I could smell the ozone, I CAREFULLY blotted several pieces of laundry onto another clean agar plate. (I blotted the laundry after it was finished in the washer and BEFORE it went in the dryer.)

The plates were incubated in my warm (about 90 degrees F) incubator for about 48 hours. 

Tips for looking at agar plates

If you have never looked at agar plates before, let me give you short lessons. The dots you see on the plates are colonies (or piles) of millions of bacteria. If there was one bacterium in the cloth that touched the plate, it would keep doubling and form one visible pile of bacteria after 24-28 hours. When there are way too many bacteria, the colonies all blend together. Many different types of bacteria grow on these agar plates. Some are harmless and some are harmful. I don't do the extra work necessary to identify specific types of bacteria. I'm just showing whether there is a lot of bacteria present or not. Mold and fungus can also grow on these plates. However, some kinds of bacteria do not grow on these plates and VIRUSES do not grow on these plates. So, just because a plate looks clean, it doesn't mean there were absolutely no live microorganisms present. Also, I don't calculate percentages of bacteria killed. These experiments are not quantitative. So, I will never be saying whether or not a product kills 99.9% of bacteria like they claim or not. My experiments are great for comparing different cleaning products or cleaning methods. My experiments are simple, and you can repeat them yourself if you want. They are great science fair projects. 

Here are the results from dirty load of laundry that was washed on a cold heavy soil cycle with no bleach. I did NOT use the PureWashPro for this load. The plate on the left is the laundry before it was washed. The plate on the right is the laundry after it was washed. The "clean" laundry still has a lot of bacteria. 

Here are the results showing a load of laundry that was washed on the cold heavy soil cycle with 1/2 cup of bleach added to the bleach dispenser. There is a HUGE decrease in the amount of bacteria. 

Just for reference, lets compare bacteria in our laundry to the bacteria in a new pair of underwear. 

When I blot the new underwear onto an agar plate, nothing grows. 


Here are pictures of the agar plates from the 3 pureWash experiments that I did. They are before and after.

Unfortunately, I could not detect any significant germ killing. The laundry smelled like ozone, and I know the machine was working. However, the laundry seemed to have about as much bacteria as any other laundry washed on cold with no chlorine bleach. My washer is a HE front loader so it uses very little water. It is possible that a top loader that actually fills up with water would generate better results for the pureWash system. Considering it is the special water that is supposed to kill the germs, maybe the laundry needs to be really submerged in this water. So, I am not saying that the pureWashPro doesn't work. I'm just saying that I couldn't see a significant decrease in the amount of bacteria in the laundry when I use the PureWash system in my HE front loader. I'm so sorry, PureWash. I tried. The PureWash company is aware of my results and are trying to figure out why they differ from their professional lab test results. I told them I would happily repeat the experiments if they come up with something that might help. If you want to see the rest of my laundry experiments, visit this page of my website.

Future Work

I have many more experiments to do! If you would like to suggest a product or experiment, please e-mail me If you would like to be informed when new results are posted, please like my facebook page. I always post on there when new results are up. If you would like to help support my work, please use my Amazon links when you shop on amazon. I have an Amazon affiliate account. If you use any of my Amazon links when you shop on Amazon, I get a small percentage of the sale. For example, you can click to Amazon using the link for my daughter's book and buy something. It doesn't matter what you buy, but I will get a small percentage of the sale. I use that Amazon money to buy agar plates and all the supplies that I need to do these experiments. If you don't want to bother using amazon links, you are welcome to send me a small donation through paypal. If you really want to brighten my day, please buy one of my daughter's books. They are excellent! If you don't have a little girl to give them to, buy a copy for your local elementary school library or children's hospital.

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If you want to read more of my experiments, please check out this list. 

Lastly, before you leave, please brush up on your knowledge of stomach bugs so you can help decrease their spread by reading this page of my website. Thank you!

--Annie Pryor, Ph.D 
phd.annie at