A hydrogen water bottle looks like an ordinary bottle and behaves like a small appliance. The difference is in the base: instead of a flat bottom, it has an electrolysis cell, a rechargeable battery, and a display. This page explains what actually happens when you press the button.
The short version
Water is two parts hydrogen, one part oxygen. Pass an electric current through it, and those parts separate. That is electrolysis, and it is the whole mechanism. A hydrogen water bottle runs that reaction in a controlled way and directs the hydrogen into the water you are about to drink.
What SPE and PEM mean
Two acronyms come up constantly in this category, and they describe the same piece of hardware from different angles.
PEM stands for proton-exchange membrane. It is a thin sheet that lets hydrogen ions pass through it but blocks the gases themselves from mixing. SPE stands for solid polymer electrolyte — the membrane doubles as the electrolyte, which means the bottle does not need any added salts or chemicals to conduct the current.
Together they do one useful job: they keep the two gases produced by electrolysis apart. Hydrogen goes into your water. Oxygen, along with any ozone and chlorine generated at the other electrode, is vented away through a separate channel rather than dissolving into what you drink. A bottle without this separation would put everything into the same water.
The four steps of a cycle
- Fill. Add clean drinking water — filtered, bottled, or reverse osmosis. Leave a few centimetres of headroom at the top so gas pressure has somewhere to go.
- Activate. Press and hold the button on the base. The display starts counting down.
- Generate. The cell runs for five minutes. You will see fine bubbles rise through the water - that is the hydrogen coming out of the membrane. The display shows remaining time, concentration in PPB, and battery level.
- Drink. The bottle stops on its own. Hydrogen is the smallest molecule there is, and it escapes from water steadily once the cycle ends, so drink it soon rather than saving it for later.
Why the water goes cloudy
The milky look during a cycle is not a fault. It is a suspension of very fine hydrogen bubbles. It clears within a minute or two as the larger bubbles rise out and the rest dissolves.
Before your first cycle
A new membrane arrives dry and needs to be rehydrated before it will work properly. Fill the bottle with warm water at roughly 40–50 °C, leave it to stand for two to three hours, then pour that water away and charge the bottle fully. Skipping this step is the most common reason a new bottle appears to underperform.
What this page does not claim
Hydrogen water is an active research area, and the quality of the evidence varies a great deal by claim. We describe what the device does — it dissolves hydrogen gas into water, and we do not make health claims about what that does for you. This is a hydration device, not a medical device, and nothing here is intended to diagnose, treat, cure, or prevent any disease.
Read next: What is a hydrogen water bottle? · What is PEM electrolysis? · Frequently asked questions