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Hydrogen Machines
Guides→Hydrogen Water Generator — Buyer's Guide

How to choose a hydrogen water generator.

The buyer's decision comes down to one question — which electrolysis technology is inside the machine. This guide compares modern PEM/SPE electrolysis with older alkaline electrolysis on the two things that actually matter: purity of the dissolved hydrogen, and safety of the drinking water it produces.

Editorial content. No disease or treatment claims are made. Hydrogen Machines products are general wellness devices.

9 minute read.

What a hydrogen water generator actually does.

A hydrogen water generator dissolves molecular hydrogen gas (H₂) into drinking water using electrolysis — the same water molecule, split into its components and then reassembled with elevated dissolved H₂. Concentration is measured in parts per billion (ppb) or milligrams per litre (mg/L); 1 mg/L is approximately 1,000 ppb at standard conditions.

Everything downstream of the buying decision — how much hydrogen the water contains, whether it also contains oxygen or trace byproducts, how the machine holds up over years of use — is determined by the electrolysis technology inside the cell. That is where this guide focuses.

Why the electrolysis technology matters.

Electrolysis splits water into hydrogen at the cathode and oxygen at the anode. The question is what happens to those two gases next. In a modern PEM/SPE (Proton Exchange Membrane / Solid Polymer Electrolyte) cell, a solid polymer membrane physically separates the two gas streams. Hydrogen is dissolved back into the drinking water on one side; oxygen is vented away on the other.

In an older alkaline electrolysis cell — the design used by many first-generation ionisers and low-cost generators — there is no membrane separation. Both gases share the same water. The drinking water can therefore contain dissolved oxygen alongside the hydrogen, and depending on source-water chemistry, trace ozone or chlorine byproducts. The pH is deliberately raised as part of the design.

For a hydrogen water generator specifically, the PEM/SPE approach is the one worth buying. Not because alkaline electrolysis is unsafe in the general sense — millions of people drink alkaline ionised water — but because you cannot honestly call a device a hydrogen water generator if it cannot guarantee what is actually dissolved in the water.

PEM/SPE vs alkaline electrolysis at a glance.

The differences that matter for a buyer:

DimensionPEM / SPE electrolysisAlkaline / plate electrolysis
Gas separationMembrane physically separates H₂ from O₂ — clean dissolved hydrogen onlyNo membrane separation — H₂ and O₂ can co-mingle in the drinking water
ElectrolyteSolid polymer membrane — no chemical additives, works with pure waterRequires alkaline solution or metal-plate electrodes — can leach ions
ByproductsOxygen vented separately. No ozone or chlorine in the drinking waterCan produce ozone or chlorine byproducts if source water contains impurities
Typical H₂ concentration1,500–5,000 ppb dissolved in the drinking waterHighly variable — often 200–1,200 ppb, rarely stated as a certified figure
pH of output waterClose to neutral — pH tracks the source waterElevated pH (8.5–10.5) as a design goal, not a byproduct
MaintenanceDistilled water only. PEM stack rated for years of daily useElectrode cleaning cycles, mineral scaling, periodic plate replacement

Deeper dive — PEM electrolysis explained →

Related — why alkaline pH and dissolved H₂ are independent properties →

Safety and purity — what to actually check.

"Safe" and "pure" are the two words used most loosely in this category. Anchor them to specifics:

Purity of the dissolved hydrogen. The dissolved gas should be molecular H₂ and nothing else. A membrane-separated PEM/SPE cell delivers that. A non-separated cell delivers a mixture — some hydrogen, some oxygen, potentially traces of ozone or chlorine depending on the source water.

Purity of the drinking water. Nothing from the electrodes or the electrolyte should leach into the water. PEM/SPE uses a solid polymer membrane and inert electrode coatings; there is no liquid electrolyte to contaminate the output. Alkaline plate designs vary — this is worth asking about.

Safety of the hardware. Look for CE, RoHS and ISO 9001 as the minimum. These describe the hardware and manufacturing quality system — not medical or therapeutic status. A hydrogen water generator is a general wellness device, not a medical device.

What certifications should a hydrogen machine have? →

Six-point pre-purchase checklist.

Apply these to any hydrogen water generator before you buy — regardless of brand, price or channel.

Confirm PEM/SPE electrolysis

Ask the seller in writing which electrolysis technology the generator uses. It should say PEM (Proton Exchange Membrane) or SPE (Solid Polymer Electrolyte). If the answer is 'plate electrolysis', 'alkaline', 'ioniser' or 'we don't know', treat that as a fail.

Published ppb output — certified, not implied

The dissolved hydrogen concentration should be published as a specific ppb (or mg/L) figure at a defined cycle time. 'High hydrogen' or 'hydrogen-rich' without a number is marketing, not a specification.

Separate oxygen venting

The design must vent the oxygen produced by electrolysis away from the drinking water. Without separate venting you are drinking a mixture of dissolved H₂, dissolved O₂ and any incidental byproducts.

Certifications on the hardware

CE is the minimum. RoHS confirms the machine is free from restricted hazardous materials. ISO 9001 confirms the manufacturer operates a quality management system. These describe the hardware and manufacturing — not medical or therapeutic status.

Source-water requirements

PEM/SPE generators require distilled or high-purity water to protect the membrane. If the manual is silent on water quality — or claims 'any tap water is fine' — the membrane lifespan claim is unlikely to hold.

Serviceability

Ask what happens at year 5 and year 10. A serviceable machine has a documented stack replacement path and available parts. A sealed unit with no service option is disposable, whatever the box says.

Where our range fits.

The HERO Dual 20 in our range is the machine designed for buyers who want both hydrogen inhalation and hydrogen-rich water from a single PEM/SPE unit. It produces 1,000 ml/min pure H₂ for inhalation via cannula, and ≥3,000 ppb hydrogen-rich water for consumption — simultaneously, from one machine.

If your primary interest is hydrogen water only, the HERO Dual 20 still applies — you would simply use the drinking-water output. The PEM/SPE architecture and the separate oxygen venting are the same features you would look for in any dedicated hydrogen water generator.

If the source water itself is the thing you want handled, the HERO Purity 200-110 is the filtration-first option: three-stage filtration (PP sediment, CTO carbon block, RO membrane) feeding a PEM cell that produces up to 2,500 ppb hydrogen-rich water. It is a drinking-water system rather than an inhalation machine. The RO systems hub covers it alongside the HERO RO Dual 10.

HERO Dual 20 hydrogen inhaler and hydrogen water generator

HERO Dual 20 Inhale + Drink All-in-One

PEM/SPE electrolysis. 1,000 ml/min pure H₂ inhalation. ≥3,000 ppb hydrogen-rich water. CE certified.

View HERO Dual 20 →

Read more.

What is hydrogen-rich water?

Plain-language explainer — what H₂ in water actually is, ppb ranges and outgassing.

Read →

PEM electrolysis explained

How the membrane separates hydrogen from oxygen and why purity depends on it.

Read →

Hydrogen vs alkaline & 'radical' water myths

Why alkaline pH and dissolved H₂ are independent properties — and why the ORP claim misleads.

Read →

How long does hydrogen water last?

Outgassing rates, container choice, and why freshness beats any storage trick.

Read →

Ready to choose a machine?

The HERO Dual 20 produces PEM/SPE hydrogen-rich water and inhalation output from a single machine. Compare it against the dedicated inhalers in our range.

View the HERO Dual 20Compare All Machines
This page is editorial content. No claim is made to diagnose, treat, cure, or prevent any disease or medical condition. Hydrogen Machines products are general wellness devices. Consult a qualified health professional before starting any new wellness routine.

Frequently asked questions

A hydrogen water generator is a device that dissolves molecular hydrogen gas (H₂) into drinking water using electrolysis. Well-designed generators use a Proton Exchange Membrane (PEM/SPE) electrolysis cell to split water into H₂ and O₂, vent the oxygen separately, and dissolve the hydrogen back into the drinking water under pressure — typically 1,500–5,000 ppb.

PEM (Proton Exchange Membrane) electrolysis uses a solid polymer membrane that physically separates hydrogen from oxygen — so only clean dissolved H₂ ends up in the drinking water. Alkaline or plate electrolysis has no membrane separation, so the drinking water may contain dissolved oxygen, ozone, or trace byproducts alongside the hydrogen. PEM also runs on high-purity water without chemical additives.

No. Water ionisers are designed to raise pH (alkaline water) using plate electrolysis. Any dissolved hydrogen is an incidental byproduct — concentration is rarely published as a certified specification. A dedicated PEM/SPE hydrogen water generator is designed specifically to maximise dissolved H₂ and typically outputs close to neutral pH.

Portable bottles typically produce 500–1,500 ppb. Mid-range PEM/SPE generators produce 1,500–3,000 ppb — the range most commonly used in published research on hydrogen water. High-output PEM/SPE generators produce 3,000–5,000 ppb. Always ask for a certified figure at a defined cycle time, not a marketing phrase.

PEM/SPE generators are designed for distilled or high-purity water. Tap water minerals can scale on the membrane and shorten stack life. Follow the manufacturer's water-quality specification — if the manual does not state one, that is itself a warning about build quality.

Molecular hydrogen dissolved in drinking water is a well-tolerated wellness format. The safety question with hydrogen water generators is about the hardware — specifically, whether the electrolysis design keeps oxygen, ozone and any electrode byproducts out of the drinking water. A PEM/SPE design with separate oxygen venting is the standard to look for.

Evidence‑Informed Engineering

HydrogenMachines™ systems are built using evidence‑informed engineering, natural materials, and transparent construction. Independent laboratory testing confirms gas purity and composition.