Can You Use Purified Water in a CPAP? (Things to Avoid)

First of all, we should understand what purified water is. Purified means that water has been filtered or RO processed to remove impurities. Distilled water is not purified since distillation is not a method of filtration. Although both distilled and purified waters are good and safe to drink.

So, can you use purified water in a CPAP? Well, distilled water is ideal for CPAP machines, but other type of purified water like Reverse Osmosis can be used as a second option if you don’t have any distilled water handy.

Distilled water for your CPAP humidifier

First of all, distilled water goes through the treatment process of distillation. That removes impurities and what’s left is the purest possible form of water. For these reasons, distilled water is used in medical facilities and laboratories. Simply speaking, as a solution to dissolve or dilute other chemicals.

Distillation works by boiling water and collecting the steam, which returns to water form upon cooling. This process is effective because evaporating steam leaves behind contaminants like bacteria, heavy metals, and minerals like magnesium and sodium.

Some CPAP machines have a humidifier attachment that actually is optional. Meaning, that the CPAP machine can perform its main functions without added water. The air coming from the machine goes through the humidifier unit as the last step before entering the tube that directly connects to the mask. This can be beneficial to increase the comfort of your night sleep. Although some very simple and lightweight CPAP machines, such as meant for traveling don’t have a humidifier at all. It’s a nice addon, rather than a key function.

Snugell distilled water for CPAP

Megahome Countertop Water Distiller to make your own distilled water

Megahome Countertop Water Distiller to purify water for CPAP

Reverse Osmosis water for a CPAP humidifier

Reverse Osmosis is among the most effective ways of purification to produce safe drinking water. In most Western countries, public drinking water is purified to make it safe for human consumption. Reverse Osmosis removes chemicals and contaminants like:

• Bacteria

• Algae

• Parasites

• Metals like copper and lead

• Fluoride

• Chemical pollutants

Reverse Osmosis water is purified and should not create any problem in your lungs. Unlike distilled water, RO water still has an amount of trace minerals. If you’ll put RO water in the CPAP machine once or twice, there should be no problem. The issue will arise after continuous use because trace minerals will collect at the bottom of the tank. Thus it is not advisable to use RO water for an extended period of time.

APEC RO-CTOP Countertop Reverse Osmosis system to purify water for CPAP

If you decide to use RO water, make sure to follow standard procedure

• Fill the tank with more water than will be used overnight. If the tank will dry out, the sediment will stick to the plastic surface.

• Empty the remaining water in the morning and wash the tank with tap water. Then leave it dry.

• If you spot some sediment forming, you can use some soap or mild detergent to wash it out.

What water to avoid in a CPAP

Because of the earlier mentioned factors, it’s best to avoid other types of water that you can find more easily around.

Tap water

The properties of tap water vary highly across cities since different water sources are utilized and different water treatment procedures are used. It’s really unclear what type of trace minerals are in various tap waters.

Well water

Private well water might be good to drink, but the same as tap water it’s hard to know what else is in it. Best to avoid well water in the CPAP machine.

Bottled water

Again, bottled water will be safe to drink, but the mineral contents of it make it not suitable for humidifiers of CPAP machines.

Boiled water

This might seem like a hack to get some clean water. While boiling water in a kettle or a pot will kill bacteria, this process is not distillation. Boiling will not remove any water minerals at all. Don’t confuse boiled water with distilled water.

Melted ice water

If you’re stuck in a hotel, it might be tempting to get a lot of ice and melt it. You might even hear that frozen and melted water is better to drink than straight tap water. There might be some truth in this argument. As most industrial and domestic ice makers will use filtered or purified water to produce ice. This is beneficial for the ice machine as purified water has less total dissolved solids. Although, freezing and melting do not change the overall chemical composition of water. Meaning that, at best, you’ll get filtered water which is not suitable for the CPAP humidifier.

Final words

You should do some planning and arrange to get distilled water. Most of the time it’s available in grocery stores. Otherwise, you can travel with your own water distilled water supplies. These days, water distillers are easily available to purchase so you can produce your own water.

Consider Reverse Osmosis only as a second option and only for brief usage.


This is my blog about the ways and solutions that can help you improve your health by taking more value from drinking water. As improving health means a lot to me, I decided to create the Water On Top project with the purpose to reveal the benefits of water, the finest products to take our daily water to another level, and much more great stuff about water that I believe is on top of our nutrition.

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