Informational Guide

Is Tap, Purified or Distilled Water Best For Humidifiers?

We explore and explain what kind of water is best for humidifiers so you can get the most out of your device and have healthy clean air in the home.

by Josh M

Humidifiers add moisture to the air in your home and help prevent dryness. Humidifiers can help support your physical and mental wellbeing, and the best humidifiers add a lot of value to your home.

At the heart of a humidifier is water, and you need the right type of water to allow the humidifier to function properly. This guide will explain what kind of water is best for humidifiers so you can get the most from it at home.

Purple Mist from Humidifier

You can use various types of water within your humidifier, but each has its pros and cons. We’ve given a quick breakdown of the main types of water and when you should use each:

Distilled Water (Top Choice)

Distilled water has been treated to remove bacteria, minerals, and other contaminants you’ll find in tap water. This makes it the cleanest choice and the best choice for a humidifier.

The purity of the water helps prevent any damage to the humidifier and allows it to operate smoothly. It also means that only clean, pure water is being added into your home, so it’s healthier for you and your family.

Purified Water

Purified water is filtered to help remove most of the minerals, bacteria, and other impurities. This makes the water pretty close to perfectly pure and a close second choice for your humidifier.

The purity of the water helps prevent any mineral build-up in your humidifier and improves the longevity of the device. It also means that clean air is pumped into your home.

Bottled Water

Bottled water isn’t recommended for your humidifier. It’s filtered to make it safe to drink, but it still contains various dissolved minerals, which is the reason different brands of water have a unique taste.

These minerals can cause damage to your humidifier and stop it from working as effectively.

Boiled Water

To distill water, you need to boil it, so boiled water is essentially the same as distilled water. If you’re boiling it yourself, you won’t get it quite as pure as if it’s done in clinical conditions, but it’s still a good option for your humidifier. Make sure you let it cool before pouring it into the device.

Demineralized Water

Demineralized water is made by filtering regular water through a mesh membrane. This removes almost all of the minerals from it and makes it much better suited for humidifiers than normal tap water.

However, some bacteria or sediments can remain in this type of water, which means these can spread into your home.

Tap Water

Tap water is not recommended in your humidifier. It contains a lot of different sediments, minerals and can contain bacteria which can damage your humidifier and impact your health. The sediments and minerals will build up in your humidifier over time and prevent it from functioning correctly.

The lack of purity in the water will also mean that the moisture being released into your home can have a negative impact on your overall health, the exact opposite of what you’re trying to achieve.

Distilled Water: Is It Best For Your Humidifier?

Distilled water is the most effective way of purifying water. It’s made by boiling the water so that all the minerals, sediments, and bacteria remain and steam rises. It’s then condensed onto a cool surface and collected. The water is then considered distilled.

Distillation Set Up

There are a few different types of humidifiers that use a variety of methods to heat the water. Steam, mist, and ultrasonic are the typical choices for home humidifiers, but you’ll find a variety on the market.

All of these humidifiers will perform better with distilled water, and studies have shown it’s the safest option for you and your family. It means that they are heating and releasing clean moisture into the air, which is beneficial to your overall health.

Distilled water is by far the best choice for humidifiers compared to other types for a couple of key reasons:

It Keeps Your Humidifier Clean

Minerals like calcium, sodium, and magnesium are found in tap water in very small quantities. Over time, these minerals will build up in the humidifier and can start to clog it. By using distilled water, you stop these minerals from entering the humidifier in the first place.

It Helps Prevent Mold Growth

Mold can destroy your home and the furniture within it. Mold spores are often found within tap water, and that can turn your humidifier into a spreader for those spores.

Once mold builds up within your device, you’ll need to replace it so that it doesn’t infect your whole home. Distilled water has all of the mold spores filtered from the water and prevents this from happening.

It Improves Air Quality In Your Home.

Humidifiers can produce dust that spreads around your home and impacts the overall air quality. This is caused by minerals and bacteria within the tap water, which is then spread throughout your home.

Using distilled prevents this from happening because the dust and bacteria are filtered out before you use it.

How Can You Make Distilled Water At Home?

You can purchase distilled water for your humidifier, but it’s possible to make it yourself at home. There’s a couple of easy methods to do this, and we’ve given step by step guides below:

Rainwater Method

This method involves gathering your rainwater and distilling it. This is a slow method of distillation which is slightly less reliable than others but will still produce results.

1. Gather the rainwater

Set a large container to gather rainwater over a few days, weeks, or months (depending on your climate).

2. Leave to distill

Leave the rainwater for 48-72 hours so that it settles. The rainwater has already been evaporated before it fell, so the sediment is separate from the water.

After leaving it for 2-3 days, all the sediment and impurities will fall to the bottom of the container and leave distilled water on the surface.

Glass Bowl Method

This is the easiest method for distilling water at home, and all you’ll need is some ice, a glass bowl, and a large pot that the bowl will fit within.

1. Fill the pot

Fill the pot about halfway and place it on a hob on the stove.

2. Set the glass bowl

Set the empty glass bowl in the pot so that it floats. If it doesn’t float, you may need a bigger pot or more water in there.

3. Heat the water

Turn on the stove and start to heat the water. Invert the lid on top of the pot and place the ice on top so that it’s a cold surface. As the water starts to evaporate, the steam will make contact with the lid and create condensation. This will then drop back into the glass bowl.

This method leaves only the pure water after the evaporation process, and the impurities will be left behind.

4. Remove the bowl

Once the water has all evaporated, you can remove the glass bowl, which will contain your distilled water.

Distillation Using Glass Bowl Method
Glass Bottle Method

This method is also pretty straightforward, but you will need to find a bottle with a curved neck. This will allow you to catch the condensation without it dripping back down.

1. Fill your bottle

Get two bottles, one with a curved neck and one regular one, and fill the regular bottle about halfway.

2. Attach the bottles

Connect the bottles together using masking tape so that the curved bottle fits into the regular one.

3. Heat the water

Place the regular bottle with the water into a pot or pan at a 30 degree angle. Turn on the heat, so the water starts to boil.

4. Cool the curved glass

Use an ice pack to cool the curved bottle. This will allow the water to evaporate from one bottle and condense into the other. Keep going until all your distilled water gathers in the curved bottle.

Distillation Using Glass Bottle Method

What Kind Of Water Is Best For A CPAP Humidifier?

CPAP stands for Continuous Positive Airway Pressure, and it’s a specific type of humidifier designed for those who suffer from sleep apnea disorders. It gives you a continuous flow of pressurized air directly through tubes and helps you breathe through the night.

A humidifier is used alongside the CPAP to help keep the air from going dry and impacting your breathing. It also helps stop any condensation within the tubes, which can happen in a cold room. The impact of a CPAP humidifier is huge and can help prevent infections, nasal congestion, inflammation, and even nosebleeds.

Manufacturers recommend using distilled water within a CPAP humidifier to help protect your health. The distilled water is free from any microbes, bacteria, or minerals which might impact the device and your health when using it.

Tap water has been found to be hazardous, and if you’re in a part of the world where you can’t find distilled water, then you should look to boil the tap water yourself.

Unlike other humidifiers, CPAP humidifiers are changed every 6 months, so there’s less risk of minerals building up. There is, however, a concern about microbes or bacteria being pumped into your respiratory system.

Distilled water is the safest and cleanest option. You should change the water in your CPAP daily for optimum performance.

CPAP Humidifier

People Also Ask (FAQ)

How long do you have to boil water for it to be distilled?

The water should be brought to a boil for about 45 mins, but as soon as it becomes steam and is then condensed and collected, it’s considered distilled.

How long do you have to boil water to kill bacteria?

It takes about 1-3 minutes to kill bacteria in boiling water.

Can I use rainwater instead of distilled water?

Rainwater can be used instead of distilled water, but it won’t be as pure as truly distilled water because there may be small amounts of impurities.

What is the difference between purified, distilled, and spring water?

Distilled water is boiled, condensed, and collected to remove all the minerals and bacteria. Purified water is filtered so that most contaminants are removed, but a small number may remain.

Springwater undergoes some filtering to remove bacteria, but generally, all the minerals are left in. Distilled water is best for humidifiers.

How often should you change the water in a humidifier?

The water in your humidifier should be changed daily to stop any contaminants or bacteria from building up within it. You should also look to clean your humidifier weekly and change filters regularly.


Humidifiers are really useful devices that will help protect your health and wellbeing, but you need to set them up correctly to get the most from them. Humidifiers are only as good as the water put into them, and not all types of water are suitable.

Distilled water is the purest and has little to no contaminants, which can impact the humidifier or you. Always look to use distilled water in your humidifier if you’re able to.

Last Updated on July 16, 2021

Josh M

My name is Josh and I am obsessed with the HVAC industry. I created this website to help HVAC techs of all levels get the best out of their heating & cooling systems. I have spent thousands of hours studying air conditioners, heaters and home air products so you can learn & buy with confidence. Learn more about the team here.