UPDATED: November 21, 2022
When my daughter was born, I was so concerned about the water that we were going to use in her formula, in her bath, and so on. And then it hit me, I had baseboard heating throughout the house which can really dry out the air. So I asked myself, what about the water in my humidifier, can I use reverse osmosis water in my humidifier?
Reverse osmosis water can be used in a humidifier if distilled water is unavailable. Unlike distilled water, RO water may still contain dissolved minerals that can build up in and damage your humidifier. Minerals in RO water can also leave deposits on surfaces where your humidifier water settles.
If your household water has a large number of dissolved solids in it, a reverse osmosis system may not be able to remove a sufficient amount of the solids contained in the water to make it ideal for use in a humidifier.
Since a reverse osmosis drinking water system only removes up to about 95% of salts and other minerals from your water, there will most likely be some leftover which is not so bad, but you may find that it will leave mineral deposits wherever the humidifier mist settles.
Why do you need to use very pure water in a humidifier?
Just think about what a humidifier is doing. A humidifier is taking water and mixes very fine droplets of it into the air that we breathe.
These droplets also settle on your skin, in your hair, on your clothes, and on your furniture and appliances. These deposited water droplets that have minerals still in them will also leave a white film that will make your furniture and appliances look like they have a layer of dust on them.
If the water that your humidifier is introducing into the air has minerals and impurities in it, these impurities will be deposited everywhere that the humidified water reaches.
These impurities mixed with water are the perfect places for bacteria to start growing, and once bacteria start to grow, it wants to multiply and become a colony of bacteria.
So, if you are putting water that has a high amount of impurities into your humidifier, you are depositing a high amount of potential ground zero points for colonies of bacteria to grow.
Some of these impurities will also remain inside the humidifier, and potentially grow into colonies of bacteria and mold right inside the humidifier itself.
These bacteria and molds can cause breathing problems such as asthma and nasal congestion.
Can reverse osmosis water in a humidifier cause allergic reactions?
Allergy sufferers may have significant reactions to molds and bacteria, and even people with no allergies at all may become sick from the regular inhaling of the unhealthy spores that these bacteria and molds release into the air.
Remember, the water that you put into your humidifier is going to get everywhere, and I mean everywhere.
If you use reverse osmosis water in your humidifier, it may not only leave mineral deposits from any minerals not removed by the reverse osmosis system, but it will deposit water that can corrode metals and other materials.
Water is often called the most universal solvent on earth. When water is very pure and neutral (having a ph of 7.0, not considered to be acidic or alkaline), it will want to absorb minerals and other deposits to balance out its aggressive nature.
Reverse osmosis water can be a very aggressive substance.
I like to call aggressive reverse osmosis water, hungry water. It reacts much like we do when we get hungry. When we feel that we are hungry, we seek out food to eat and satisfy our hunger. This is very similar to what aggressive water does.
Aggressive reverse osmosis water is water that is lacking in overall balance.
Water likes to have minerals and other solids in it, so as it flows over, under, and around substances that contain minerals that it can absorb, it will absorb these minerals until it has reached the maximum saturation that it can hold.
What this means when using reverse osmosis water in a humidifier is that the water will land on everything in the area of the humidifier and if the water can absorb minerals from what it lands on, it will.
Remember that the whole reason that you use a reverse osmosis drinking water system is to remove impurities and minerals from your water. And since water does not like to have the minerals that it has absorbed stripped away, it will immediately try to absorb new minerals.
So if you are going to use reverse osmosis water in your humidifier, be sure to only use it in areas where you do not have surfaces that can corrode due to aggressive water.
Metal, stone, concrete, or any surfaces that you are concerned about getting affected by corrosion from reverse osmosis water should be covered to prevent any contact with the reverse osmosis water being used by your humidifier.
Why is distilled water preferred over reverse osmosis water in humidifiers?
Distilled water is the preferred water to be used in humidifiers because it has zero or nearly zero impurities in it.
See my article Is boiled water better than reverse osmosis water?
A reverse osmosis system, although great for removing minerals from water, will generally remove approximately 95% of the minerals, or TDS (Total Dissolved Solids) from the water that is being processed by the system.
Why is distilled water preferred overall for use in humidifiers?
The process of reverse osmosis is for the reduction of total dissolved solids but not the complete removal of the total dissolved solids contained in water.
Reverse osmosis water can be used in a humidifier. Although distilled water is the preferred choice to be used in humidifiers because it is extremely pure and free of minerals, reverse osmosis water can be an alternative to distilled water if the final product water is pure enough.
If you are lucky enough to have water that contains less than 100 parts per million of Total Dissolved Solids, which is relatively good water, to begin with.
Your reverse osmosis water should be in the area of about 5 or less. This water is not 100% free of dissolved solids, but this tiny amount should not cause significant scaling that would create any problems with your humidifier.
It is the dissolved solids that are in the water that cause the mineral built-up inside humidifiers. This scaling build-up can inhibit the humidifiers’ ability to disperse the water in the fine droplets that it is supposed to create.
What is water TDS?
TDS is an approximate count of how many dissolved solids are in a sample of water. I say “approximate” because it is measured by the electrical conductivity of the water sample.
Pure water that is totally free of any minerals will not conduct electricity as well as water with lots of minerals in it. So it is important to understand that the TDS count of a water sample is not an exact number of minerals present, but more of a general number to gauge the purity of the water.
To give you an idea of common amounts of TDS in water, bottled waters that we commonly buy in stores may have a TDS as low as 5 or so, but others may be as high as 50 or more.
A bottle of water with a TDS of 50 may not sound very good, but most people consume water with a TDS of 50 or higher regularly, and it is still considered to be perfectly acceptable to drink.
The United States Environmental Protection Agency (EPA) considers any TDS up to 500 parts per million (PPM) to be satisfactory for consumption.
This does not necessarily mean that water with TDS above 500 is harmful to your health, but when water with a TDS count of 500 parts per million or more is used, it will most likely change the way your food or drinks taste.
So if your house tap water that is feeding into your reverse osmosis system has a TDS of 100, you can expect the outgoing water coming from the system to have a TDS count of about 5 to 10. Although this water is much better than unprocessed water, it still has some minerals left in it.
If you would like to know the TDS in your water, check out my recommended DIY Water Testing Kits for a simple-to-use TDS meter that you can use right at home.
Can I use reverse osmosis and distilled water in my humidifier?
Some people use distilled water as well as reverse osmosis water in their humidifiers. Alternating from distilled water to reverse osmosis water will help to keep the humidifier cleaner and reduce mineral deposits that can develop into bacteria and molds.
How effective alternating distilled water and reverse osmosis water is will depend on the total dissolved solids that are present in the reverse osmosis water.
It is very simple to find out what amounts of total dissolved solids are in your water. You can purchase a TDS meter to check your water regularly. They are quite inexpensive and very easy to use.
Simply pour a small amount of the water that you wish to test into the TDS meter well, and insert the meter. A digital display will tell you what your TDS reading is in just a few seconds.
If your total dissolved solid count in the water coming from your reverse osmosis system is relatively low (I recommend less than 20), you should be fine using it in your humidifier.
But no matter what water you are using in your humidifier, you should clean the humidifier’s tank and discharge tube regularly. It is very easy to do and only takes a few minutes.
How do I clean minerals from RO water from my humidifier?
You can easily clean your humidifier using some hydrogen peroxide solution that is available at your local drug store or even at most grocery stores.
Check out this quick video on how to clean your humidifier.
First, unplug the humidifier and empty out any unused water in the storage tank.
Dry the storage tank with a clean cloth or paper towel.
Use a mild concentrate of 3 percent hydrogen peroxide solution or simply use 1 tablespoon of white vinegar to 32 ounces of water, and wipe down the humidifier’s storage tank and any parts that are in contact with the water mist that the humidifier puts out.
Do not add any type of cleaner to the water in the storage tank and then run the humidifier in order to clean it. This will be putting the cleaning solution into the air and is not recommended.
Make cleaning your humidifier a weekly routine if you use it constantly. If you only use it at night or a few days a week, you should be cleaning it more often as it will be exposed to air for long periods of time which is when bacteria and molds will tend to grow.
Cleaning your humidifier twice a week should only take you a few minutes, and is well worth the effort.
But isn’t reverse osmosis water acidic?
This is a great question, and yes, reverse osmosis is usually acidic. I say usually because some reverse osmosis systems use a mineral cartridge to add calcite to the water.
Calcite will neutralize the acid in the water and also add some flavor to the water, making it more enjoyable to drink. It will also add to the total dissolved solids in the water so it is not advisable to use it in your humidifier.
Most reverse osmosis systems leave the water acidic because reverse osmosis removes the minerals that take the acid out of the water. This acidity in the water should not be a problem when using it in a humidifier.
Actually, the acid in reverse osmosis water will tend to inhibit the growth of bacteria and molds while any mineral deposits are still exposed to acidic water. But the reverse osmosis water will soon dissipate the acidity when it is exposed to air and quickly become neutral or non-acidic.
So yes, reverse osmosis water is generally acidic, but no, it should have no effect whatsoever on the performance of your humidifier. If you would like to know more about why reverse osmosis water is acidic, check out my article Does reverse osmosis change water pH?
Can reverse osmosis water be used in CPAP?
A Continuous Positive Airway Pressure or CPAP machine is basically a humidifier that goes straight over your nose and mouth. Whatever water you put into your CPAP is the water that you will be breathing into your lungs.
Although reverse osmosis water is quite pure and should not create any problem in your lungs, the minerals that are in your water may cause havoc with your CPAP machine.
Since reverse osmosis does not always remove all of the dissolved solids and minerals in your water, I do not advise using reverse osmosis water in your CPAP at all. If you need to use your CPAP and you do not have any distilled water available, use the highest-purity bottled water that you can find.
So, to summarize.
Yes, you can use reverse osmosis water in your humidifier if your total dissolved solids count coming from the system is relatively low. I recommend that you use a TDS meter so you know just what levels of dissolved solids you have in your reverse osmosis systems water even if you do not use it in your humidifier. Just so you know that you are drinking good water.
If your total dissolved solids count coming from your reverse osmosis is 20 or more, I highly recommend that you use distilled water only or perhaps a diluted mix of the distilled water and the reverse osmosis water.
Clean your humidifier often, and the area around the humidifier is clean and dry, and don’t let the humidity get too high where you are using the humidifier.
Related Questions:
Brita water in a humidifier? Using water from a Brita water filter may or may not be beneficial to use in your humidifier.
Brita states that their basic filter does not filter out bacteria, so if the water going into the filter has bacteria, chances are that you are going to be misting that bacteria directly into the air by putting it into a humidifier.
Brita filters use coconut carbon in their filters along with the water-softening resin. The coconut carbon removes chlorine which is used to sanitize municipal water supplies and can help with bad tastes and unpleasant odors.
Carbon will get saturated as it filters and loses its ability to remove particles, so replace your filter often.
The water-softening resin uses ion exchange to remove minerals like calcium, magnesium, copper, cadmium, and zinc. This will soften your water for a period of time, but once the softening resin is covered with minerals, it will lose its effectiveness.
How to make distilled water for a humidifier. A very simple way to produce distilled water for your humidifier is called the “Glass Bowl Method”. Fill a large pot with water and then float an empty glass bowl that is a little smaller than the pot in the water.
Bring the water in the pot to a boil and place a glass dome top (upside down) on the pot. Cover the upside-down cover with ice and let the distilled condensate collect into the bowl floating in the water.
How to soften water for a humidifier. If you already have a water softener, great! But the softened water may still have high levels of salt and other minerals in it. I recommend using a reverse osmosis drinking water system to remove the majority of the minerals in the water before using it in a humidifier.
Do you put hot or cold water in a humidifier? Although the thought of a nice warm mist coming from your humidifier may sound good, warm mist in the air can encourage bacteria growth in your home, shorten the life of your humidifier and hot water around kids is never a good idea.
Using cold water will give the same benefits that warm water will and is normally preferred over hot water.
Using hot water can also damage your Brita filter, see my article on Does hot water ruin a water filter?
Can you put a humidifier next to your bed? Absolutely! You can put a humidifier pretty much anywhere that you like, but keep a few things in mind when placing your humidifier.
I always recommend putting a humidifier on a sturdy surface that is clear of clutter so there are no places for the settling mist to accumulate and potentially begin growing bacteria or mold.
Place your humidifier on a cloth tablecloth and wash the tablecloth weekly if you are using the humidifier daily. Putting the humidifier right next to your bed will not really help to humidify the area as the humidifier’s mist should add humidity evenly throughout the area.
