You can carbonate water at home without any special equipment by using yeast and sugar, which produces carbon dioxide through fermentation. This is the same basic process used to carbonate champagne and beer. Other approaches exist too, but fermentation is the most accessible method that requires nothing beyond pantry ingredients and a sturdy bottle. Here’s how each method works and what to watch for.
The Yeast and Sugar Method
Fermentation is the simplest way to naturally carbonate water. Yeast consumes sugar in a sealed container and produces CO2 as a byproduct. That gas dissolves into the water, creating fizz. The process takes roughly 24 to 48 hours at room temperature.
The key ratio: for every 1 gram of sugar, yeast produces about 0.46 grams of CO2 and 0.48 grams of alcohol. To carbonate 1 liter of water to a level comparable to store-bought sparkling water (around 5 volumes of CO2, or 9.8 grams per liter), you’d need roughly 21 grams of sugar. That amount of sugar also produces about 10 grams of ethanol, which works out to around 1% alcohol by weight. That’s a small but real amount, roughly comparable to kombucha.
If you want less alcohol, use less sugar. You’ll get lighter carbonation, but even half the sugar (about 10 grams per liter) will produce noticeable fizz at around 0.5% alcohol. Champagne yeast works well because it ferments cleanly without adding strong flavors, but standard bread yeast will also work. You only need a tiny pinch, roughly 1/8 teaspoon per liter.
Step by Step
- Choose your bottle. Use a plastic soda bottle (not a random water bottle). PET soda bottles are designed for carbonated beverages and handle 2.5 to 5 bars of pressure, with burst ratings of 6 to 8 bars (87 to 116 psi). Glass bottles rated for carbonation work too, but standard glass bottles that weren’t designed for pressure can shatter.
- Dissolve sugar in water. Add 10 to 21 grams of sugar per liter of room-temperature water and stir until dissolved. More sugar means more fizz and more alcohol.
- Add yeast. Sprinkle in a small pinch (1/8 teaspoon) of champagne or bread yeast. Swirl gently.
- Seal and wait. Cap the bottle tightly and leave it at room temperature (around 68 to 75°F). Leave minimal headspace in the bottle to maximize how much CO2 dissolves into the water rather than collecting as gas above it.
- Check pressure. If you’re using a plastic bottle, squeeze it periodically. When it feels rock-hard and you can’t dent it with your thumb, the carbonation is ready. This typically takes 24 to 48 hours.
- Refrigerate immediately. Move the bottle to the fridge as soon as it’s firm. Cold temperatures do two things: they slow the yeast down (stopping further fermentation) and help the water hold more dissolved gas. Open it cold for the best fizz.
Why Cold Storage Matters
Cold water holds significantly more dissolved CO2 than warm water. Gas molecules move more slowly at lower temperatures, so they stay trapped in the liquid longer. This is why a warm soda goes flat almost instantly once opened, while a cold one stays bubbly.
For homemade sparkling water, refrigerate the sealed bottle for at least a few hours before opening. Keep it upright so the smallest possible surface area of water is exposed to the headspace gas. After opening, reseal it tightly and return it to the fridge. Even with good practices, homemade carbonated water will lose fizz faster than commercial versions because it lacks the precise pressurization of industrial equipment.
Improving the Taste
Plain carbonated water made with yeast can taste slightly yeasty or have a faint sweetness from residual sugar. A few adjustments help.
First, chill and then carefully pour the water off the sediment at the bottom. The yeast settles out over time, especially in the fridge. Pouring slowly leaves most of it behind. Second, consider adding a small amount of mineral salts before fermentation to give the water more body and a flavor profile closer to commercial sparkling mineral water.
The mineral content of bottled sparkling water varies enormously. A study comparing 126 brands across Europe found calcium levels ranging from as low as 2.9 mg/L (Sant’Anna from Italy) to 581.6 mg/L (Meltinger from Switzerland). Magnesium ranged from about 7 mg/L to 52 mg/L depending on the country. For a simple homemade version, a pinch of baking soda (sodium bicarbonate) per liter adds a slight mineral flavor and helps neutralize any acidity. A tiny amount of food-grade calcium or magnesium salts, available from brewing supply shops, can push the flavor closer to European-style mineral water.
Bottle Safety
Pressure is the main safety concern with any home carbonation method. Fermentation doesn’t stop until the yeast runs out of sugar or the environment becomes inhospitable, so the pressure inside a sealed bottle keeps climbing as long as the yeast is active.
Standard PET soda bottles are your safest option. They’re engineered for internal pressures of 2.5 to 5 bars during normal use and won’t burst until 6 to 8 bars. If something goes wrong, a plastic bottle will bulge and eventually split rather than explode into sharp fragments. Glass bottles designed for carbonated beverages (like flip-top Grolsch-style bottles or champagne bottles) handle 4 to 7 bars, but standard glass jars, wine bottles, or decorative bottles should never be used. They can burst violently.
Never leave a fermenting bottle at room temperature for more than 48 hours, and never use more sugar than the recipe calls for. If you forget a bottle on the counter for several days, open it very slowly over a sink, pointing it away from your face. Refrigerating it first for a few hours will slow gas release and make opening safer.
Other Methods Without Equipment
Dry ice (solid CO2) can carbonate water quickly. Drop a small piece into a container of cold water and the CO2 sublimates directly into gas, dissolving into the liquid. This works fast and produces no alcohol, but handling dry ice requires gloves and good ventilation because it can cause frostbite and displaces oxygen in enclosed spaces. Never seal a container with dry ice still sublimating inside, as the pressure buildup is rapid and unpredictable.
Vinegar and baking soda reactions generate CO2, and some DIY setups pipe this gas into water through tubing. The concept works, but the volume of CO2 produced per batch is small, the gas often carries vinegar vapor (affecting taste), and it’s difficult to build enough pressure for real carbonation without purpose-built fittings. Most people who try this method find the results underwhelming compared to yeast fermentation.
How Nature Does It
Naturally sparkling springs, like those in parts of Europe, get their carbonation from deep geological processes. Underground, carbonate rocks like limestone and marble are exposed to extreme heat (150 to 200°C) and pressure from tectonic activity. This breaks down the rock and releases CO2 gas, which dissolves into groundwater as it travels upward through fault lines. The resulting water is naturally fizzy and picks up minerals along the way, which is why famous sparkling mineral waters have distinctive flavors tied to the geology of their source.
You can’t replicate that at home, but the underlying chemistry is the same as every carbonation method: get CO2 into contact with water under pressure, and it dissolves. Cold temperatures and higher pressure both increase how much gas the water absorbs. Whether that CO2 comes from yeast, dry ice, or ancient limestone, the fizz is identical.