What Kind Of Water Should You Use To Wash Windows

Hot or warm purified water is the most effective kind of water at cleaning windows as it removes grease, dirt and salts without leaving any streaks, water spots, or mineral deposits. Cold purified water is also effective at cleaning windows but purified hot water also kills surface bacteria and mold.

No one wants to spend a long time cleaning windows and the kind of water you use can make a big difference. Most of us wash our windows 2-4 times a year (max!) and business owners wash their windows monthly to weekly! With the right cleaning water and a little effort, you can make the boring job of cleaning any window much easier than you probably expect.

In this article, I discuss in more detail why cleaning your windows with hot/warm purified water is the best option. I also briefly discuss other window cleaning related topics, like what the professionals use (including water type and cleaning products), how to get rid of smears and streaks, how to wash car windows, using ionizing water and much more!  To clean your windows like a pro, keep reading.

The Right Kind of Water to Use on Windows

Purified water is the best kind of water to use on windows. The main reason why you should use purified water instead of regular tap water is that tap water can leave unwanted mineral deposits, water spots, streaks, and smears on your windows.

Tap water contains impurities such as calcium and magnesium (scale-forming minerals), sodium, iron, and copper, which can all make washing windows take longer and leave them looking dirty.

Purified water, such as water from a reverse osmosis system or distiller, doesn’t contain minerals or other impurities which guarantees faster and more efficient cleaning. Using purified water means you won’t have to come back and re-clean your windows after washing them. 

Purified water, even without a detergent, is extremely effective at cleaning windows. It is capable of removing dirt, grit and grease and can remove organic matter and other water-based ionic contaminants.

Soft Water For Cleaning Windows

Soft water contains 0 to 60 mg/L calcium carbonate. Your tap water may already be naturally soft, but the majority of U.S. households (and private well owners) have hard (121-180 mg/L) to very hard (>180 mg/L) water.

Soft water is preferred over hard water for cleaning windows as its low mineral content does not leave water spots, lathers soap more easily, and is more effective at removing dirt and grease.

Water softeners work by substituting out the calcium in hard water with other minerals such as sodium or potassium. While this solves the problem of too much calcium and scale build up in appliances, washing windows with softened water can still leave water spots and streaks through the build up of sodium or potassium salts.

Soft water is better at forming a good soap lather compared to hard water. This is because hard water minerals are preferentially taken up by soap molecules, which means the soap will not lather very well. As the soap molecules are essentially “used up”, there is also less soap molecules available to remove dirt and grease from your windows.

Hot or cold water?

Most professional cleaners and DIY homeowners use cold water to clean the windows since you don’t have to keep refilling with hot water.

However, if you use purified water that is HOT or WARM it makes cleaning much easier and will give better results than cold water, and this is why.

Removes grease more easily

Have you ever tried washing greasy dishes with cold water? Good luck – it can be very frustrating just using cold water!

Using hot water on greasy dishes is soooo much faster!!. The same goes for grease on windows. Using hot water is a much more effective way to get rid of any grease from your windows.

You may be thinking, “but I don’t have grease on my windows”. You’d be surprised! Go into your kitchen and wipe the window with a clean paper napkin, I can guarantee you it will have grease on it.

Removes dirt more easily

Hot purified water is much more effective at removing dirt from windows than cold water. Hot water will reduce the amount of time you have to clean your windows and in turn, and it saves on water.

Kills bacteria

When cleaning your windows, you not only want to remove dirt and grease but also kill any living bacteria. Hot temperatures are a perfect and effective way to kill bacteria on your windows.

Hot water doesn’t guarantee that your windows will be 100% germ-free, but it’ll be much more effective than cold water. Perfect for kids who love to touch windows!

Kills mold

Mold is common on and around windows as it they often get a steady supply of moisture from condensation or an open window. They are also kept warm by small amounts of sunlight hitting the glass.

Hot water is great at killing mold on windows. Mixed with some soap and the water will do 90% of the job at killing and removing mold from around windows. Add a little vinegar or commercial mold killer to help keep the mold from returning quickly.

However, sometimes what can look like white mold growing on windows is actually salt build-up.

Removes salt build-up

Salt build-up on windows is obviously common when your near the coast, but you can get all kind of salt from other sources, such as:

  • Concrete
  • Agricultural areas
  • Dust
  • Well water
  • etc. etc.

Hot water will quickly dissolve and get rid of salt from your windows. Additionally, purified water is capable of dissolving salts more rapidly and taking them away compared to regular tap or well water.

Reduces drying time and leaves no streaks

Hot water obviously dries more quickly than cold water. This means if you use purified hot water on your windows, you won’t get any mineral or other deposits left behind. You can also leave the windows to quickly dry by themselves.

Purified water that is hot not only reduces the drying time but also leaves no streaks on the glass surfaces.

Better for cleaning windows during winter

If you live somewhere cold, using warm water is great for cleaning windows during the winter months.

Let’s face it, keeping your hands warm while washing windows is just way more enjoyable!

Also, warm water will not freeze quickly and allow you to do a thorough cleaning job.

Try and avoid using HOT water when it’s really cold out. A rapid thermal shock on the window from HOT (boiling) water may crack the glass. Stick to warm water and you should have no problems.

Water That Professional Window Cleaners Use

Professional window cleaners use soft water as it doesn’t contain minerals that can leave water spots, streaks, smears, and make the glass look hazy after washing.

Many window cleaning professionals create soft water through purification processes such as reverse osmosis (RO), distillation, and deionization. Using any or a combination of these water purification processes eliminates almost all mineral content and sediments from regular tap water, creating contaminant-free pure water.

If you don’t have access to RO water, distilled water is just as good for cleaning windows. Water distillers will remove all mineral content and leave your windows residue free.

For hard-to-reach windows, use purified water combined with water feed poles. Professional window cleaners use these to easily and efficiently clean high windows and skylights. Water feed poles make life sooo much easier, especially if you have any high windows.

Professional window cleaners also use a good squeegee and will clean them regularly. I’m talking cleaning the squeegee after every window!

They also replace the rubbers on the squeegee regularly to save working time and keep windows streak free. If the rubbers on your squeegee go hard, then it’s definitely time to replace them.

What Do Professional Window Cleaners Use IN Their Water

Different professional window cleaners have their own secrets of achieving a streak-free and crystal-clear window cleaning finish. However, there are some common cleaning products professionals use in their window washing water, including:

  • Dish soap
  • Glass cleaners (like Windex Glass and Window Cleaner)
  • Etching salt
  • Trisodium Phosphate (Heavy duty cleaner).

In freezing or sub-freezing temperatures, professionals often add some anti-freeze chemicals in their cleaning water to prevent it from crystallizing in the bucket or on the windows. 

Other options to stop your window cleaning water from freezing is to add a little alcohol cleaner and/or vinegar.

Ionized Water for Cleaning Windows

Ionized water can be an effective at cleaning glass windows due to its low mineral content and high pH that draws out dirt and grime. Ionized water quickly takes up any unwanted compounds from its surroundings – in this case from the window glass.

Ionized water refers to the kind of water that has been processed using a filtration process that removes close to 100% of all minerals and it also raises the pH level (becomes more alkaline).

This makes ionized water an excellent and efficient window cleaner agent. Since ionized water has had almost all of its mineral content removed, it leaves behind no spots, residue, stains, or streaks on windows after cleaning.

So, if you have access to a water ionizer machine at home, you can use the water on your windows.

Best Way to Clean Windows Without Streaking

Sometimes you may notice some streaks left behind after cleaning your windows? Here’s some things that you may want to consider to get you a streak-free finish:

  • First hose off any lose dirt and dust from the outside of windows
  • Use purified water, soft water (naturally low mineral content – mainly calcium and magnesium), distilled water, or ionized water.
  • Use hot/warm water if possible
  • Try using vinegar in the water to help cut grease.
  • Use microfiber cloths.
  • Add alcohol and vinegar to the water in freezing conditions.

How To Get Rid of Smears on Windows

The following tips will help you get rid of smears on your windows and give them a spotless, crystal clear finish:

  • One tip I learned from a professional cleaner was to use Newspaper rather than a cloth to get rid of soap smears. I honestly didn’t believe it at first, but IT REALLY WORKS!
  • Use clean microfiber cloths, water and vinegar. The vinegar is a weak acid and helps to remove any minerals or other deposits left behind on the glass.
  • Try a mirror cleaning spray.

How To Clean Auto Glass Without Streaking

Cleaning the auto glass without leaving streaks is essential not only for a good look but for your safety – The last thing you need when driving into the sun is to not see through the window properly!

Below I’ve put together a list of some tips to help you clean your auto glass without streaking.

  • Avoid cleaning in direct sunlight – the water dries faster and limits the amount of time you have to remove the water. If you let water dry naturally on cars or boats, you’ll often get water spots or streaks left behind.
  • Use a low-pile microfiber cloth
  • Avoid using well water on your car due the high mineral and contaminant content.
  • Always pre-wash and rinse your car with a hose that is fitted with a hose filter.
    • For a TON more information on hose filters and their various uses, check out this article I wrote here.
  • Use an auto glass cleaning spray.
  • Use a moistened microfiber towel to wipe any obvious streaks left on the glass – don’t forget to check the side mirrors.
  • Use a clean dry microfiber towel to do a final wipe of the glass.

Water Purification Guide has more information on well water and washing cars available here.

Final Thoughts

Windows are essential parts of your house that unfortunately need regular cleaning. By using soft/purified water, microfiber cleaning materials, cleaning spray, and a little effort, you’ll clean your windows like a pro and achieve a streak-free, crystal-clear finish.

Russell Singleton

Russell has a Bachelor of Science (Environmental and Marine Geoscience) with Class I Honors. He is currently completing his doctorate in science and is passionate about all earth processes, especially isotope geochemistry and paleohydrology.

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