Chlorine-Free Pools — Is It Possible, and What Does It Cost?

What does “chlorine-free” actually mean?

The phrase is used loosely, and that is the single biggest source of confusion when people shop for a chlorine free pool. Three very different things get sold under the same words.

1. Genuinely chlorine-free. No chlorine compound is dosed into the water at all. Disinfection comes from something else entirely — oxidation by active oxygen, ozone, or nanobubble-driven oxidation. This is what most people mean when they say chlorine-free.
2. Chlorine generated on site. A salt chlorinator dissolves salt in the water and electrolyses it into hypochlorous acid. The result is chlorine — you simply make it yourself instead of delivering it in drums. It is a real convenience and safety improvement, but the water still contains chlorine.
3. Reduced chlorine. A secondary system — UV, ozone or nanobubbles — carries most of the disinfection load, and a small chlorine residual is kept for regulatory or safety reasons. Bathers notice a dramatic difference; the paperwork still says chlorine.

All three are legitimate choices. They are not the same product, and a supplier who blurs them is not helping you decide.

The problem with chlorine: skin, eyes, airways and chloramines

Chlorine is effective, cheap and extremely well understood. That is why it has been the default for a century, and any honest guide has to start there. The problems are not with chlorine as a disinfectant — they are with what it produces once it meets what swimmers bring into the water.

When free chlorine reacts with sweat, urine, skin cells, cosmetics and sunscreen it forms chloramines — combined chlorine. Chloramines are the actual cause of most of the complaints blamed on “too much chlorine”:

• The sharp chlorine smell in an indoor pool hall. Well-run pools smell of almost nothing; a strong smell usually means high combined chlorine, not high free chlorine.
• Stinging eyes and red eyes after swimming.
• Dry, tight or itchy skin, and flare-ups for people with sensitive skin, eczema or a chlorine rash.
• Airway irritation, which matters most for competitive swimmers, instructors and staff who spend hours a day at the water’s edge.
• Green tint in light-coloured hair, and accelerated wear on swimwear, ladders, handrails and ventilation ductwork.

Why this is a facility problem, not just a comfort problem

For a private pool, chloramines are an annoyance. For a public pool, a hotel or a swim school, they are an operating cost: extra ventilation capacity, faster corrosion of the building fabric, complaints, and staff sick-leave. That is the calculation that makes a chlorine free pool sanitizer worth investigating even when the chemical bill alone would not justify it.

The five alternatives to chlorine

Here is what is actually on the market, described the way a buyer needs to hear it — including what each one does badly.

1. Active oxygen (hydrogen peroxide / MPS)

A chemical free pool in the sense that no chlorine is dosed: active oxygen compounds oxidise organic material instead. Water feels soft, and there is no chlorine smell at all.

Honest limits: active oxygen breaks down quickly, especially in warm water and sunlight, so dosing has to be frequent and consistent. Its disinfection power against some pathogens is weaker than chlorine, which is why it is rarely approved on its own for a busy public pool. Best suited to small indoor pools, spas and private pools with light, predictable loads.

2. Salt chlorinators

Salt is the most popular “chlorine alternative” in the world, and it is worth being precise: a salt system is a chlorine system. Electrolysis converts dissolved salt into hypochlorous acid — the same active disinfectant as liquid chlorine — and the cell recycles it back to salt afterwards.

What it genuinely solves: no drums of chemical to store, handle or transport, a very stable low residual, and water that feels noticeably softer at around 3 g/l salinity.

Honest limits: chloramines still form, because free chlorine is still present. The cell is a consumable and scales up in hard water. Salt is corrosive to some stone, grouting and untreated metal fixtures. If your goal is to eliminate chlorine, this is not it. See Nanobubbles vs salt chlorinator for the detailed comparison.

3. UV

Ultraviolet light inactivates microorganisms as water passes the lamp, and it is genuinely excellent at one specific job: destroying chloramines that have already formed. Many public pools add UV purely to fix air quality in the hall.

Honest limits: UV only works inside the reactor. It leaves no residual in the pool basin, so it cannot stop person-to-person transmission between swimmers, and regulations therefore almost always require a chemical residual alongside it. Lamps need replacing and the quartz sleeve needs cleaning. UV is a superb component and a poor complete answer — more in Nanobubbles vs UV.

4. Ozone

Ozone is a far stronger oxidiser than chlorine and leaves no lasting by-products — it reverts to oxygen. It is outstanding for clarity, removing organics and cutting chemical demand.

Honest limits: ozone is a gas, and the whole engineering challenge is dissolving it efficiently and then removing the excess before the water returns to the basin. Conventional injection wastes a large share of the gas, and off-gassing has to be handled properly because ozone is hazardous to breathe. It also leaves no residual in the basin. Covered in depth in Nanobubbles vs ozone.

5. Nanobubbles

Nanobubbles are gas-filled bubbles under roughly 200 nanometres across — thousands of times smaller than a grain of salt. Unlike ordinary bubbles they do not rise and burst; they stay suspended for days, carrying a strong negative surface charge and an enormous combined surface area.

That surface area is the point. It lets a nanobubble system transfer oxygen or ozone into water far more completely than coarse injection, and the collapse of individual bubbles drives oxidation that physically disrupts pathogens and breaks down organic load. Read the underlying science on How nanobubbles work.

Honest limits: it is a treatment-loop technology, so like UV and ozone it acts on water passing through the system. Capital cost is higher than a drum of chlorine, and it is the newest of the five, so there is less of an installed base to reference than salt or UV. It suits facilities where chemical reduction, air quality and water clarity have real financial value.

Method	Removes chlorine?	Residual in basin	Chloramines	Running cost	Best fit
Chlorine (baseline)	No	Yes	Forms readily	Lowest	Any pool; the default everywhere
Active oxygen	Yes	Short-lived	None	Medium–high (frequent dosing)	Small indoor pools, spas, private pools
Salt chlorinator	No — makes chlorine on site	Yes	Still forms	Low, plus cell replacement	Private and hotel pools wanting no chemical storage
UV	No — needs a residual	None	Destroys existing ones	Low, plus lamp replacement	Public pools fixing hall air quality
Ozone	Largely	None	Prevents formation	Medium	High-load pools, high clarity demands
Nanobubbles	Yes, or greatly reduced	None on its own	Prevents formation	Low after installation	Facilities where air quality and chemical cost matter

Running cost is indicative and varies with bather load, water temperature, local energy and chemical prices, and how the plant is operated. Ask any supplier — including us — for figures against your pool volume and turnover rate rather than a generic table.

How nanobubbles deliver chlorine-free disinfection

A nanobubble system sits in the circulation loop, after filtration. Water passes through the generator, which creates billions of ultrafine bubbles carrying oxygen or ozone.

1. Generation. The generator produces nanobubbles at high density. Because they are so small, buoyancy barely acts on them and they stay in suspension rather than surfacing.
2. Gas transfer. The enormous combined surface area dissolves far more gas into the water than coarse bubbles, which mostly escape at the surface before transferring anything.
3. Oxidation. Bubble collapse releases concentrated oxidative energy at the microscopic scale, disrupting cell membranes of pathogens and breaking down the organic compounds that would otherwise become chloramines.
4. Clarity. The negative surface charge helps lift fine particles and biofilm off surfaces so the filter can remove them, which is why operators usually notice the water looks different before they look at any test results.

The practical outcome for a swimmer is water with no chlorine smell, no stinging eyes and no tight skin afterwards. The practical outcome for an operator is less chemical purchasing, lower combined chlorine, and less corrosive load on the building. The engineering detail is on the NanoSWIM Pool System page, and the application-specific version is under swimming pool water treatment.

What does a chlorine-free pool cost?

There is no honest single number, because a 25-metre municipal pool and a hotel plunge pool are not the same purchase. What is predictable is the shape of the cost.

• Capital cost. Every alternative to chlorine costs more up front than dosing pumps and drums. Nanobubbles, ozone and UV are equipment purchases; active oxygen and salt are cheaper to install.
• Chemical spend. This is where the money comes back. Cutting chemical use substantially against a conventional dosing regime changes the annual budget line permanently, and chemical prices only move one way.
• Energy. Modest and continuous. Worth asking every supplier for kW draw at your flow rate, then multiplying by your own tariff — not theirs.
• Maintenance and consumables. UV lamps and salt cells are scheduled replacements. Ask what wears out, how often, and what it costs — before you sign, not after.
• Indirect savings. Lower ventilation load, slower corrosion of fixtures and ductwork, fewer complaints, and in commercial settings a genuine guest-experience difference. These are real but harder to put on an invoice, so treat them as upside rather than the core case.

A useful rule when comparing quotes: ask for total cost over five years, including consumables and energy, on your actual pool volume. Any supplier who cannot produce that is quoting a box, not a solution.

Rules and regulations in Norway

Public pools in Norway operate under the bathing-facility regulations (forskrift om badeanlegg, bassengbad og badstu), which are enforced by the municipal health authority. The regulation sets requirements for water quality and monitoring rather than prescribing one specific technology — but the practical consequence for a chlorine free swimming pool is important:

• A public pool generally has to maintain a measurable disinfectant residual in the basin so that contamination introduced by one bather cannot be passed to another before the water is circulated.
• That means a genuinely zero-chlorine public pool is rare. The realistic outcome is a strongly reduced chlorine level, with nanobubbles, ozone or UV carrying the disinfection load.
• Private pools, hotel pools and spas are treated differently and have far more freedom to run fully chlorine-free.
• Whatever you install, documentation matters: municipal buyers ask which standards a system complies with, and how the results are logged.

We keep the compliance detail — which standards apply, what is documented, and what a municipal buyer will ask for — on Standards and compliance. If you are specifying a municipal facility, the public aquatic facilities page is written for that procurement process.