Shopping for a pool sanitation system means sorting through a lot of claims. Five myths come up more than any other: that a strong chlorine smell means clean water, that salt pools are chlorine-free, that chlorine kills every germ, that UV or ozone removes the need for chlorine, and that AOP replaces chlorine entirely. Here is what the evidence says about each.
Myth 1: A strong chlorine smell means the pool is clean
Verdict: false. A strong “chlorine” smell usually means the water is full of chloramines.
Chloramines form when chlorine binds with the sweat, urine, lotion and other body waste swimmers bring into the pool. The CDC says chloramines irritate the skin, eyes and respiratory tract, and that they off-gas into the air, especially at indoor pools. Chlorine that has bound into chloramines is also chlorine that is no longer available to sanitize.
Two habits keep chloramines down: a quick rinse before swimming, which the CDC says “removes much of the body waste that helps form chloramines,” and a sanitation system that breaks down contaminants before they combine with chlorine. Read more in what causes pool chlorine smell and how to get rid of it.
Myth 2: Salt water pools are chlorine-free
Verdict: false. A salt water pool is a chlorine pool that makes its own chlorine.
A salt chlorine generator passes lightly salted pool water through an electrolytic cell, which converts the salt into chlorine. That chlorine sanitizes the water the same way added chlorine does, and it can form chloramines the same way too. Salt systems are convenient because you handle less product, but the water still holds a chlorine residual. Our salt water pool guide covers the pros and cons in detail.
Myth 3: Chlorine kills every germ in the pool
Verdict: false. Chlorine handles most germs quickly, but some are highly tolerant of it.
The biggest example is Cryptosporidium (Crypto), a parasite that causes diarrheal illness. The CDC’s most recent national report, Outbreaks Associated with Treated Recreational Water, 2015 to 2019, found:
- 208 outbreaks linked to pools, hot tubs and water playgrounds, causing at least 3,646 illnesses, 286 hospitalizations and 13 deaths
- Crypto caused 76 outbreaks, 49% of those with a confirmed cause, and 84% of the illnesses in those outbreaks
- Crypto can stay infectious for more than 7 days in water held at 1 ppm free chlorine
Because standard chlorine levels cannot stop Crypto quickly, many aquatic facilities add a supplemental treatment step. In an independent university study, Clear Comfort’s hydroxyl-based AOP reduced chlorine-resistant Crypto by up to 99.99% (4-log).
Myth 4: UV or ozone makes a pool chlorine-free
Verdict: false. UV and ozone treat water inside the equipment, and the pool still needs a chlorine residual.
UV systems disinfect water as it passes through a lamp chamber, and ozone systems inject ozone gas into water in the equipment room. Both work only on the water flowing through them. Ozone “does not provide a long-lasting residual, so it cannot be used as the primary sanitizer,” as WaterWorld explains, and the same is true of UV. Water in the pool itself still relies on chlorine. For a side-by-side look, see supplemental treatment options compared and UV vs hydroxyl-based AOP.
Myth 5: An AOP system replaces chlorine
Verdict: false, and we say that as the company that makes AOP systems. AOP lets a pool run on much less chlorine, but the pool still needs a low residual.
Clear Comfort’s AOP creates hydroxyl radicals that break down contaminants and germs as water circulates, which lets a pool run a much lower chlorine residual. A chlorine-only pool typically runs around 3 to 5 ppm of free chlorine. With AOP, the typical residual is about 0.5 to 1.5 ppm, as explained in our beginner’s guide to pool chlorine. That lower level is why AOP pools have less chlorine smell and less irritation, while still meeting the need for a residual sanitizer.
Frequently asked questions
Does a pool that smells like chlorine have too much chlorine?
Usually it has too many chloramines, which form when chlorine reacts with sweat, urine and other body waste. The fix is better sanitation and a quick rinse before swimming.
Is a salt water pool better than a chlorine pool?
A salt pool is a chlorine pool with an on-site chlorine generator. It saves you from handling chlorine, but the water still has a chlorine residual and can still form chloramines.
How long can Crypto survive in a chlorinated pool?
The CDC reports that Crypto can survive for more than 7 days in water kept at 1 ppm free chlorine with normal pH.
Does a pool with AOP still need chlorine?
Yes, at a much lower level. Hydroxyl-based AOP handles most of the oxidation and germ control as water circulates, and a low chlorine residual of about 0.5 to 1.5 ppm protects the water in the pool itself.
Want a pool that runs on less chlorine? Compare our home pool systems or aquatic facility systems.
