UPDATED: March 19, 2022
You use your humidifier nearly every day to keep the air in your home from being dry and to help keep your home feeling warm and comfy. But what about those days when you don’t use your humidifier, is it OK to leave the unused water in your humidifier?
It is OK to leave water in a humidifier for a short time providing that it is free of minerals and impurities that may encourage bacteria growth or cause the working parts of the humidifier to malfunction.
Distilled, Reverse Osmosis, and Zero Water are usually fine to leave in a humidifier.
Leaving water in your humidifier for a short time may not be any problem at all as long as there is nothing in the water that could cause harm to the humidifier or to your health.
Some water is perfectly fine to leave in your humidifier while other water should be removed when your humidifier will not be in use for a long period of time.
When Should You NOT Leave Water In A Humidifier?
Water will often contain hard minerals and dissolved solids that are usually not visible to the human eye, but they can cause all kinds of problems if they settle inside a humidifier.
- Water containing hard minerals like Calcium or Magnesium (commonly called Hard water) can leave a white film of hard minerals when the water evaporates and the same calcium or magnesium can also settle on the inside of a humidifier causing the internal moving parts to malfunction.
- Dissolved solids such as sodium (salt) can also accumulate inside of a humidifier causing parts to malfunction or corrode.
Any water that has NOT been purified may contain impurities that may damage a humidifier or worse, lead to the growth of bacteria within the humidifier that could later get projected into the air that you breathe by the humidifier.
Some Common Types Of Water And Why They Can Or Should NOT Be Left In A Humidifier!
| Type Of Water | OK To Leave In Humidifier? | For How Long? | Why? | What To Do? | Better Alternative! |
|---|---|---|---|---|---|
| Distilled Water | Yes | Up to 1 year if stored properly | 0 Impurities | Remove water when the humidifier is no longer needed | None |
| Reverse Osmosis | Yes | Up to 6 months if stored properly | Very low level of impurities | Remove water when the humidifier is no longer needed | Distilled Water |
| Zero Water | Yes | Up to 6 months if stored properly | Very low level of impurities | Remove water when the humidifier is no longer needed | Distilled Water |
| Brita Water | Yes | 5-7 days | The number of impurities varies | Remove water when the humidifier is not in use | Distilled or Reverse Osmosis Water |
| Tap Water | Yes | Varies | The number of impurities varies | Remove water when the humidifier is not in use | Distilled or Reverse Osmosis Water |
Can You Leave Distilled Water In A Humidifier?
The process of distillation leaves water free of hard minerals and dissolved solids.
This means that there are no impurities left in the water that could damage a humidifier or encourage the growth of bacteria.
Distilled water is not only the preferred water to use in a humidifier but you can also leave unused distilled water in a humidifier when it is not in use for a long period of time because it is free of impurities.
Can You Leave Reverse Osmosis Water In A Humidifier?
Water that has come from a properly working reverse osmosis system has had its dissolved solids reduced by up to 98% in many popular reverse osmosis systems.
Because reverse osmosis water is often nearly free of impurities, it can be left in a humidifier for quite a long time without the risk of damaging the humidifier and with minimal risk of developing bacteria growth for several days if not months.
Can You Leave Zerowater In A Humidifier?
Despite what many people think, Zerowater filtered water is not the same as distilled or reverse osmosis water but it is a good alternative for use in a humidifier.
A Zero water filter removes nearly all of the hard minerals from your water that could harm your humidifier and nearly all of the dissolved solids from your water that could cause issues with a humidifier (source).
So although Zero water is not quite as pure as distilled water or water from a reverse osmosis drinking water system, it is OK if Zero water is left in a humidifier for a short period of time.
Can You Leave Brita Water In A Humidifier?
A Brita water filter does not reduce dissolved solids in water but can reduce hard minerals in the water which makes it usable in a humidifier.
But because a Brita water filter contains carbon that can be a favorable place for bacteria to grow, it is not recommended to leave Brita filtered water in a humidifier for any length of time that could allow bacteria to grow.
Can You Leave Tap Water In A Humidifier?
Generally, you should not use unfiltered tap water in a humidifier and you certainly should not leave unfiltered tap water in a humidifier for more than just a few hours.
Tap water can vary dramatically from place to place and if your tap water has a high amount of impurities in it, these impurities could cause serious damage to a humidifier.
Before you use your tap water in your humidifier, you should test your water for:
- Hardness, which can leave a hard white layer of hard minerals on the internal parts of your humidifier and the surfaces in your home where the humidifier mist settles.
- Total Dissolved Solids (TDS), which can leave a build-up of dissolved solids (like salt) inside of your humidifier as well as on any surface where your humidifier mist lands.
- Iron, which can gradually form a layer of iron rust in the internal parts of your humidifier and also leave a reddish-brown on the surfaces inside of your home where your humidifier mist ends up.
If any impurities are present in your tap water, you should NOT leave your tap water in your humidifier for even a short time as these impurities could cause damage to your humidifier in only a short amount of time.
To Sum Up:
In general, if you are not sure if you should leave water in your humidifier, pour it out and save it for when you need it again or use it for another purpose and then fill your humidifier with fresh water when you need to use it again.
Water that has been distilled or has been purified using a reverse osmosis filter may be left in a humidifier providing that it has had nearly all of the impurities removed from it.
If you test your tap water and find that it has water hardness, high TDS, or iron in it, you should NOT leave it in your humidifier.
You can easily test your water for hardness, TDS, and iron with a complete water test kit or with a specific Water Hardness, TDS, or Iron testing kit.
