Water becomes alkaline when it contains dissolved minerals or undergoes a process that reduces the concentration of hydrogen ions, pushing its pH above 7 on the 0-to-14 scale. A pH of 7 is neutral (pure water), anything below is acidic, and anything above is alkaline. Most water sold or described as “alkaline” falls between pH 8 and 9.5, though the specific minerals dissolved in the water matter just as much as the number on the pH scale.
Dissolved Minerals Are the Primary Driver
The most common reason water is naturally alkaline is contact with mineral-rich rock. As water flows through limestone, chalk, or volcanic formations, it picks up minerals like calcium, magnesium, potassium, and bicarbonate. These dissolved minerals react with hydrogen ions in the water, neutralizing acidity and raising the pH. Spring water and artesian well water often have a naturally elevated pH for exactly this reason.
Bicarbonate is the key player. It acts as a buffer, meaning it doesn’t just raise the pH momentarily; it gives the water the ability to resist becoming acidic again. This distinction between pH and alkalinity is important. pH measures the current concentration of hydrogen ions, while alkalinity measures the water’s buffering capacity, or how well it can neutralize acid over time. Water can have a high pH but low alkalinity if it lacks bicarbonate and carbonate minerals. That kind of water shifts back toward neutral easily. Water with genuinely high alkalinity, rich in bicarbonates, holds its elevated pH much more stubbornly.
Electrolysis and Water Ionizers
Water ionizers are countertop devices that use electricity to split water into two streams: one alkaline and one acidic. The process is called electrolysis. When electrical current passes through the water between two electrodes, hydrogen gas forms at one electrode and oxygen gas at the other. The reactions also produce hydroxide ions on one side and hydrogen ions on the other. The hydroxide-rich stream comes out as alkaline water, while the acidic byproduct is typically discarded or used for cleaning.
For electrolysis to work effectively, the water needs some dissolved minerals to conduct electricity. Pure distilled water doesn’t ionize well because it lacks the ions needed to carry the current. This is why many ionizer manufacturers recommend using tap water or mineral-supplemented water as the starting point. The resulting alkaline water also tends to have a negative oxidation-reduction potential (ORP), which is a measure of the water’s tendency to donate electrons. Proponents point to negative ORP as an indicator of antioxidant potential, though the practical health significance of this property remains debated.
Adding Alkaline Substances Directly
The simplest way to make water alkaline is to dissolve something alkaline in it. Baking soda (sodium bicarbonate) is the most accessible option. A small amount, roughly half a teaspoon in a glass of water, raises the pH noticeably. Baking soda also adds genuine buffering capacity because it introduces bicarbonate ions. The tradeoff is added sodium, which can be a concern if you’re watching salt intake.
Commercial alkaline water products often use mineral additives instead. Calcium hydroxide, magnesium oxide, or proprietary mineral blends are mixed into purified water to reach a target pH. Some products use coral calcium or trace mineral drops marketed specifically for this purpose. The underlying chemistry is the same in every case: introducing a substance that either releases hydroxide ions or absorbs hydrogen ions from the water.
pH vs. Alkalinity: Why the Difference Matters
A common point of confusion is assuming that a high pH reading automatically means the water has strong alkaline properties. It doesn’t. Researchers at the University of Massachusetts have noted that water with a high pH causes few measurable effects if it has low alkalinity, because it has little ability to neutralize acidity. Think of pH as a snapshot of the water right now and alkalinity as its staying power.
An alkalinity test measures the combined levels of bicarbonates, carbonates, and hydroxides, usually reported as parts per million of calcium carbonate. Water that scores high on this test will maintain its elevated pH even when it encounters something acidic, like stomach acid. Water that merely has a high pH but lacks buffering minerals will quickly be overwhelmed and revert to a lower pH on contact with acid. This is why naturally mineral-rich alkaline water and artificially ionized water can behave very differently once you drink them.
What Happens in Your Body
Your body maintains blood pH in a tightly controlled range around 7.35 to 7.45, and no amount of alkaline water changes that. Your kidneys and lungs handle acid-base balance with remarkable precision. So the health claims around alkaline water are more nuanced than “it makes your body less acidic.”
That said, a few specific findings are worth noting. Lab research published in the Annals of Otology, Rhinology & Laryngology found that water at pH 8.8 with natural bicarbonate permanently inactivated pepsin, the digestive enzyme responsible for the tissue damage in acid reflux. The buffering capacity of the bicarbonate-rich water far exceeded that of conventional drinking water. This doesn’t mean alkaline water treats reflux disease, but it suggests a plausible mechanism for symptom relief in some people.
A separate study on exercise recovery found that people who drank electrolyzed high-pH water after strenuous, dehydration-inducing exercise had a 6.3% reduction in blood viscosity, compared to 3.36% with standard purified water. Thinner blood flows more efficiently, which could theoretically improve oxygen delivery during recovery. The study was small and specific to post-exercise conditions, so it’s not evidence for everyday benefits.
Where Tap Water Falls on the Scale
Municipal tap water in the United States is typically managed to fall between pH 6.5 and 8.5, the range recommended by the EPA as a secondary drinking water standard. These guidelines are non-enforceable and exist mainly to prevent cosmetic and aesthetic issues like pipe corrosion (from overly acidic water) or mineral scaling and bitter taste (from overly alkaline water). Most tap water lands between 7 and 8, meaning it’s already slightly alkaline in many areas, especially those with limestone-rich geology.
Well water pH varies more widely depending on local geology. If your well water runs through calcium-heavy bedrock, it may naturally sit above pH 8. If it filters through granite or sandstone, it can be slightly acidic. A simple home test kit can tell you where your water falls, and knowing both the pH and the alkalinity gives you a much more complete picture than either number alone.