Alkaline water has a pH above 7, with most commercial brands falling between 8 and 9.5. On the pH scale, which runs from 0 to 14, pure water sits at a neutral 7. Anything above that is alkaline (also called basic), and anything below is acidic.
How the pH Scale Works
The pH scale measures how acidic or basic a liquid is, running from 0 (strongly acidic) to 14 (strongly alkaline). Each whole number represents a tenfold difference in acidity or alkalinity, so water at pH 9 is ten times more alkaline than water at pH 8. Regular tap water typically falls between 6.5 and 8.5, which is the range the EPA recommends as a secondary standard for public water systems. That means your tap water may already be slightly alkaline depending on where you live and what minerals are naturally present.
The World Health Organization notes that most drinking water worldwide sits within that same 6.5 to 8.5 range, though some systems allow water up to pH 9.5 depending on local conditions and pipe materials.
Common pH Levels in Bottled Alkaline Water
Most bottled alkaline water is marketed at a pH between 8 and 10, with pH 8.8 and 9.5 being especially common on labels. These numbers are meaningfully higher than typical tap water, but the practical difference depends on more than just pH. The mineral content of the water, particularly calcium, magnesium, potassium, and sodium, plays a role in both how alkaline the water is and how stable that alkalinity remains over time.
Testing of popular commercial brands has shown significant variation in actual mineral concentrations. In one university analysis comparing several brands, mineral-rich waters like Fiji had the highest levels of calcium, potassium, magnesium, and sodium, while other brands marketed as alkaline contained lower amounts. The minerals matter because they act as natural buffers. Water with a high pH but few dissolved minerals may not stay alkaline once it interacts with your stomach acid.
Natural vs. Artificially Raised pH
Water becomes alkaline in two fundamentally different ways. In nature, water picks up minerals like calcium and magnesium as it flows over rocks and through underground springs. This gives it a naturally elevated pH along with a stable mineral profile. Some spring waters emerge from the ground at pH 8 or higher without any processing.
Artificially alkaline water is made through electrolysis, a process that uses electricity to split water molecules. During electrolysis, the water separates at two electrodes: hydrogen gas forms at one side and oxygen at the other, while hydroxyl ions (the chemical basis of alkalinity) concentrate in the drinking water portion. Home water ionizers use this same principle. Some bottled brands instead add mineral compounds directly to filtered water to raise the pH, which the Mayo Clinic notes is a common practice for commercially sold alkaline water.
The key distinction is stability. Naturally alkaline water holds its pH because the dissolved minerals act as buffers. Ionized water without significant mineral content can lose its elevated pH relatively quickly after exposure to air or mixing with other substances.
What Happens When You Drink It
Your stomach is highly acidic, typically around pH 1.5 to 3.5, which means it neutralizes most of the alkalinity in any water you drink. This is why drinking alkaline water doesn’t significantly change your blood pH, which your body keeps tightly regulated between 7.35 and 7.45 regardless of what you consume.
One area where the pH of the water itself may matter is acid reflux. Research published in an otolaryngology journal found that water at pH 8.8 permanently inactivated pepsin, the stomach enzyme responsible for the burning damage in reflux disease. This suggests a potential benefit for people with reflux specifically, though it doesn’t mean alkaline water treats the underlying condition.
Safety at Higher pH Levels
For most people, drinking water in the pH 8 to 9.5 range causes no problems. However, side effects including nausea and vomiting have been reported with regular consumption, according to Poison Control. In 2020, a more serious outbreak of liver disease was linked to a specific brand of alkaline water, with affected individuals developing abdominal pain, lethargy, confusion, and jaundice.
Concentrated alkaline drops, sold online for adding to regular water, carry their own risks. These products are caustic in undiluted form. In one reported case, a man who accidentally spilled alkaline drops on his skin developed a third-degree chemical burn that required treatment at a specialized burn center. If you use these products, handling them carefully and following dilution instructions exactly is important.
Water with an extremely high pH, above 10 or 11, moves beyond what any regulatory body considers appropriate for drinking water and can irritate your digestive tract. Sticking within the 8 to 9.5 range that most commercial products target keeps you well within the bounds of what the body can handle without difficulty.