Ozone Water Treatment: How Ozone Systems Work, What They Remove and What They Cost

By SubcontractorHub Editorial Team·Published September 2026

Ozone is not new. Municipal plants and bottled water producers have used it for decades. What changed is that residential and light commercial ozone systems became reliable enough for private wells, where they compete with chlorine injection, air injection and hydrogen peroxide. This guide explains how the equipment works, where ozone is the right choice and where it is overkill, and how to size it. The last section is for water treatment dealers quoting these systems.

1. How an Ozone Water Treatment System Works

Ozone (O₃) is oxygen with a third atom attached. That extra atom is unstable, which makes ozone a powerful oxidizer and also means it cannot be stored. It has to be made on site, and a typical whole-house system has five parts:

1. Generator. Most units use corona discharge: dry air, or oxygen from a concentrator, passes through a high-voltage electrical field that splits oxygen molecules. Oxygen feed produces considerably more ozone than room air. Smaller units use UV lamps, which make less.
2. Injector. A venturi in the water line creates suction that draws the gas in and mixes it. A check valve keeps water from backing into the generator.
3. Contact or retention tank. Ozone needs a few minutes of contact time to oxidize metals and sulfur and to disinfect. Many residential systems recirculate water through the injector and a contact tank on a loop.
4. Off-gas vent. Undissolved ozone and air collect at the top of the tank and are released through a vent valve, either outdoors or through an ozone destruct unit.
5. Backwashing filter. Oxidized iron, manganese and sulfur are now solid particles. A backwashing media or carbon filter traps them, and carbon also removes remaining ozone before the water reaches the pressure tank and taps.

2. What Ozone Removes, and What It Does Not

Removes or treats

• Iron and manganese, including higher levels that overwhelm air injection. The EPA secondary standards are 0.3 mg/L iron and 0.05 mg/L manganese. See the iron filter guide for the lower-cost options.
• Hydrogen sulfide, the rotten egg smell, covered in why does my water smell like rotten eggs.
• Color and tannins, by breaking down organic matter. See tannins in water for when a resin unit is the simpler answer.
• Bacteria and viruses, in the contact tank.
• Many taste and odor compounds.

Does not remove

Ozone does nothing for hardness, nitrate, sodium, fluoride or total dissolved solids. It converts arsenic to a form that is easier to filter, but arsenic still needs an adsorptive arsenic media or reverse osmosis after it. It is not a lead or PFAS treatment. Hard water still needs a softener after the ozone filter, sized with the water softener sizing calculator.

3. Ozone vs Chlorine vs Air Injection vs Hydrogen Peroxide

All four are oxidizers followed by a filter. Oxidation strength is the standard oxidation potential in volts, a rough guide to how hard each one works on iron, manganese and sulfur. Costs are typical US installed ranges including the filter after the oxidizer.

Air injection is the cheapest and handles moderate iron and light sulfur. Chlorine is the choice when the water needs a lasting residual, and the chlorine injection system sizing calculator works out feed rate and contact tank size. Ozone and peroxide earn their price on heavy iron, strong hydrogen sulfide, iron bacteria or tannins, and they add no chemical taste. Ozone has no refill chemical, while peroxide is simpler to install but needs ongoing peroxide purchases.

4. No Residual, and the Bromate Question

Ozone decays back to oxygen within minutes in water, faster when the water is warm. That means no chlorine taste, and it also means nothing protects the water after the filter. On a well with a history of coliform bacteria, many dealers put a UV system after the ozone filter as a final barrier. The water will be clear at that point, which UV needs. Size it with the UV water sterilizer sizing calculator.

Bromate is the byproduct to check for. When source water contains bromide, common near coasts and in some brackish aquifers, ozone can oxidize it to bromate, which the EPA regulates at a maximum contaminant level of 0.010 mg/L. Test bromide before quoting ozone. If it is present, an alternative oxidizer is often the safer recommendation. Chlorine has its own byproducts: with tannins and other organics it forms trihalomethanes, regulated at 0.080 mg/L total.

5. Worked Example: Sizing an Ozone Generator

Generators are rated in grams of ozone per hour. The sizing logic is ozone demand in mg/L times water flow. Commonly used stoichiometric figures are about 0.43 mg ozone per mg of iron, 0.88 per mg of manganese and around 3 per mg of hydrogen sulfide. Real systems need more than the chemistry because not all injected ozone dissolves.

Two things move the answer. Hydrogen sulfide dominates, so a sulfur spike after a dry spell can outrun a generator sized on one low test. Tannins and other organics add demand that a bench test or the manufacturer’s sizing software should capture. Recirculating systems can use a smaller generator than inline ones, because they treat stored water over a longer cycle instead of at peak flow. The well water treatment system selector helps decide whether ozone or a simpler oxidizer fits the test results.

6. Maintenance and Costs

• Generator cells: inspect and clean on the manufacturer’s schedule. Moisture in the feed air is the main enemy, so the air dryer or desiccant needs service too.
• Check valves and injector: the most common failure point. Replace check valves on schedule; a failed one lets water into the generator.
• Off-gas destruct: destruct media wears out, and vent lines should be checked for condensation and leaks.
• Filter media: backwash settings checked each visit; media replaced every several years.
• Monitoring: many systems include an ORP sensor or ozone leak monitor, which makes service visits faster.

A whole-house residential ozone system with its filter typically installs for $2,500 to $6,000, more for oxygen-fed units or high sulfur. Running costs are mostly electricity and service parts, with no chemical refills. For the rest of the treatment train, the whole house water filter cost calculator gives installed ranges.

For Water Treatment Dealers

Ozone is a premium quote, and it sells on the in-home water test. The customer with 4 ppm iron and a strong sulfur smell has usually already tried a cartridge filter or an air injection unit that could not keep up. Showing the iron, manganese and hydrogen sulfide numbers, the ozone demand math and the bromide result on the proposal is what justifies the price over a cheaper oxidizer.

It also fits a tiered proposal: air injection for the budget option, peroxide or chlorine in the middle, and ozone with UV at the top, each with its operating cost spelled out. The service plan is where ozone pays off long term, since generator cells, check valves, destruct media and filter media all have schedules. Much of the install, including the contact tank, bypass, drain and vent runs, is plumbing work.

SubcontractorHub is software for water treatment dealers: proposals that carry the water test results, good-better-best system options, e-signature and recurring service scheduling in one place.

Frequently Asked Questions

Related Guides & Tools

• Why Does My Water Smell Like Rotten Eggs?
• Iron Filter for Well Water
• Tannins in Water
• Well Water Treatment System Selector
• Chlorine Injection System Sizing Calculator
• UV Water Sterilizer Sizing Calculator
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