How-To
How to Make Hypochlorous Acid at Home
A step-by-step guide to how to make hypochlorous acid at home with a countertop generator, salt, water and vinegar, then check ppm and pH.
An HOCl generator—also called a hypochlorous acid machine—is an electrolysis device that makes hypochlorous acid (HOCl) from water, salt and, when directed, a small amount of vinegar. Instead of buying a bottle, you run a measured batch in a machine built for this purpose, then check concentration (ppm) and pH. This article explains what happens in the cell, why pH matters, and how a home unit such as the Eco One is set up to do that work.
What the machine is doing
The core of an HOCl generator is an electrolysis cell. Food-grade salt (sodium chloride) dissolved in the water supplies chloride. When the power unit drives current through the cell, part of that chloride is converted to free chlorine, which in water is present as hypochlorous acid (HOCl) and hypochlorite ion (OCl⁻). The Eco One manual calls the result electrolyzed water; the molecule this guide is about is HOCl.
That chemistry is pH-dependent. HOCl is the undissociated acid form. As pH rises, more of the same chlorine is present as hypochlorite ion (OCl⁻) instead. As pH falls too far, chlorine gas can leave the solution. A 2008 CDC guideline (p. 41) describes this pH-dependent balance between HOCl and OCl⁻. HOCL LLC’s target for batches from its manuals is pH 5–6. Distilled vinegar is the acid adjustment those directions use to land in that window—not a substitute for testing.
A hypochlorous acid machine does not “add HOCl” from a cartridge. It generates the species in place from the salt you add, the water you start with, the run time you select and the pH of the finished solution.
Batch machines versus continuous-flow machines
Home and small-facility generators come in two broad layouts:
- Batch pitchers and tanks hold a fixed volume, run for a set time, and stop. The Eco One makes a 1 L batch in a 1.5 L pitcher (fill to the 1 L line). A larger example in HOCL LLC’s lineup is the Hypo 7.5, a 7.5 L (the manual also calls it 2 gallons) batch unit.
- Continuous-flow units are typically plumbed in place, take a feed of water and brine, and produce solution as long as they run within their installation limits. Those machines have different electrical, hardness and plumbing requirements than a pitcher.
The working principle—electrolysis of a chloride solution, then pH control and testing—is the same idea. The difference is volume, installation and how you time a run. If you are choosing among models, see Choosing an HOCl Generator.
What happens, step by step, in a home batch
On a pitcher unit such as the Eco One, a typical 200 ppm liter looks like this:
- Water. Fill to the 1 L line molded on the pitcher (about mid-height), not to the top. The manual recommends water hardness under 80 ppm and notes that results vary with water quality.
- Salt. Add the manual’s dose. For the Eco One, that is 2 g of food-grade, non-iodized kosher salt per liter for a 200 ppm batch.
- Vinegar. For a 200 ppm Eco One batch, add 1 teaspoon of 5% distilled vinegar and aim for pH 5–6. For a 500 ppm Eco One batch, add 2 teaspoons of 5% distilled vinegar before the 40-minute run, still at pH 5–6.
- Electrolysis. Setting 3 runs 8 minutes and generates 100 ppm at the 1 L line; run it twice (16 minutes) for 200 ppm. Setting 2 (5 minutes) generates 60 ppm and Setting 1 (3 minutes) 40 ppm.
- Test. Chlorine paper (10–200 ppm on the Eco One’s paper) and separate pH paper. For readings above the paper’s range, the Eco One manual’s method is a 1:5 dilution: 1 part HOCl + 4 parts water, then multiply the reading by 5.
The lid is part of the Eco One directions. Empty and rinse the pitcher after use, keep it out of the dishwasher, and dry the connector before the next run. The unit uses its supplied detachable power unit.
None of those times is a substitute for a paper reading. A generator’s program is a starting method; ppm and pH confirm what you actually made.
Why pH is part of “how it works”
People sometimes treat ppm as the only number that matters. In this chemistry, pH decides which chlorine species you have at that ppm.
- pH 5–6 is the target window in HOCL LLC’s Eco One and Hypo 7.5 directions.
- pH 4–5 is not an automatic reason to discard a batch, but its shelf life will be very short.
- Below pH 4 is too low: chlorine gas can be released. Do not keep or use a batch in that range.
That is why a hypochlorous acid machine is paired with two tests, not one. PPM and pH Basics walks through the papers and the 1:5 dilution. HOCl Storage and Shelf Life covers what to do after the run.
The cleaner pathway on the Eco One
The Eco One can run a second, separate process: a potassium hydroxide (KOH) cleaner, made from food-grade potassium carbonate instead of salt. Among HOCL LLC’s current machines, only the Eco One makes that cleaner. Do not mix salt and potassium carbonate in one pitcher; the two products are not a single solution. Label the KOH cleaner clearly. The KOH cleaner is strongly alkaline. Wear gloves, keep it away from children, and never mix it with HOCl, bleach or other cleaning products.
What the machine is not
An HOCl generator is not a bottle of pre-made solution, and HOCL LLC does not sell bottled HOCl. The machine is also not a “set and forget” appliance: the Hypo 7.5 manual, for example, calls for daily leak and wire checks and monthly scale checks, and HOCL LLC does not describe that model as maintenance-free. This guide does not state a guaranteed electrode or cell life for any model; see each model’s manual and warranty.
If you want a home-scale hypochlorous acid machine for 1-liter batches, the Eco One is the unit this site walks through in How to Make Hypochlorous Acid at Home. Keep test paper on hand so each run is checked, not assumed.