You can make distilled water for your CPAP machine at home using either a stovetop setup with a large pot and a collection bowl, or a countertop distiller that automates the process. Both methods work by boiling water, capturing the steam, and condensing it back into liquid, leaving minerals, bacteria, and other contaminants behind. Here’s how each method works and what you need to know to do it safely.
Why Your CPAP Needs Distilled Water
Tap water, bottled water, and even boiled water contain dissolved minerals like calcium and magnesium. When your CPAP humidifier heats that water overnight, the minerals stay behind and form a white, crusty buildup on the chamber walls and heating plate. Over time, this reduces humidifier performance and shortens the lifespan of CPAP components. It can also cause airway irritation from aerosolized mineral particles.
The pathogen concern is just as important. Water systems can harbor bacteria like Pseudomonas, Legionella, and nontuberculous mycobacteria, organisms responsible for roughly 120,000 hospitalizations and 7,000 deaths annually in the United States from waterborne diseases, according to CDC data. A warm, moist CPAP humidifier chamber is an ideal growth environment for these organisms. Distilled water eliminates both the mineral and microbial problem at the source.
The Stovetop Method
This is the simplest approach and requires no special equipment. You need a large stainless steel pot with a domed lid, a heat-safe glass or metal bowl that fits inside the pot without touching the water, and ice.
Fill the pot about one-third full with tap water. Place the collection bowl inside, floating on the water or resting on a small rack so it sits above the waterline. Invert the pot lid so it sits upside down on the pot, creating a concave surface on top. Bring the water to a steady simmer (not a rolling boil, which can splash tap water into the collection bowl). Place ice on top of the inverted lid. As steam rises, it hits the cold lid, condenses into droplets, and drips down the curve of the lid into the collection bowl below.
This method is slow. Expect to collect roughly 1 to 2 cups over 30 to 45 minutes, depending on your pot size and heat level. Since a CPAP humidifier chamber holds about 300 to 400 milliliters (roughly 1.5 cups), one stovetop session can produce enough for a single night. You’ll need to replenish the ice on the lid periodically as it melts. Pour the melted ice water off and add fresh ice to keep condensation efficient.
Using a Countertop Distiller
If you use a CPAP every night, a countertop water distiller is a more practical long-term option. These units cost between $80 and $200 and work the same way: an electric heating element boils water in a stainless steel tank, steam travels through a cooling coil, and purified water drips into a glass or BPA-free collection jug.
A typical home distiller uses a 1,000 to 1,500 watt heating element and produces about 1 liter of distilled water per hour. A full 4 to 5 liter batch takes roughly 4 to 5 hours. Most units shut off automatically when the tank runs dry. At average electricity rates, a gallon costs about 25 to 35 cents in energy, which adds up to significant savings over buying gallon jugs at the store week after week.
One downside: distillers produce noticeable heat and a low hum while running. Many people run theirs during the afternoon or early evening so the water is ready and cooled before bedtime.
Why Boiling Alone Isn’t Enough
Boiling tap water kills microorganisms, but it does nothing to remove dissolved minerals and salts. In fact, boiling concentrates those minerals because some of the water evaporates while everything dissolved in it stays behind. Boiled tap water will still leave mineral deposits in your CPAP humidifier chamber. Distillation is different because you’re collecting only the steam, which leaves the minerals in the original pot.
Filtered water from a pitcher or refrigerator filter also falls short. Carbon filters remove chlorine and some contaminants but let most dissolved minerals pass through. Reverse osmosis systems come closer to distilled-quality water, but even they may leave trace minerals depending on membrane condition.
Storing Homemade Distilled Water
How you store your distilled water matters almost as much as how you make it. Use food-grade glass containers or food-grade plastic containers with tight-fitting lids. Glass is ideal because it doesn’t degrade and won’t allow gases or vapors to pass through the walls. Avoid reusing plastic milk jugs, as fat residues can cling to the interior even after washing.
For best quality, use stored distilled water within six months. Once you open a container, use the water within one to two days. Label your containers with the date you filled them. Keep them in a cool, dark place away from direct sunlight, which can promote algae growth in any water that picks up even a trace of contamination.
For nightly CPAP use, the most practical routine is to distill a batch once or twice a week, store it in a clean glass jug with a lid, and pour fresh water into the humidifier chamber each evening. Empty and rinse the chamber every morning so it doesn’t sit with stagnant water all day.
Tips for Cleaner Results
If you’re using the stovetop method, start with cold tap water rather than hot. Hot water from your tap has often sat in a water heater where it can pick up higher concentrations of dissolved metals. Use a stainless steel pot, not aluminum, which can leach into the water at high temperatures.
With a countertop distiller, clean the boiling chamber after every few cycles. You’ll notice a ring of white mineral scale at the bottom of the tank. A mixture of white vinegar and water, left to soak for a few hours, dissolves this buildup easily. Most manufacturers recommend this cleaning step every one to two weeks depending on how hard your tap water is.
Regardless of your method, always pour distilled water into a clean, dry container. Even a small amount of tap water residue in the storage jug reintroduces the minerals you just spent time removing.