Chlorine kills most germs in a properly treated pool within minutes, but only when the chlorine level and pH stay in range, and a few germs survive it for days. Most of the “chlorine smell” and red eyes people blame on chlorine come from chloramines, which form when chlorine reacts with what swimmers bring into the water.
These seven pool chlorine facts cover what chlorine does, the levels CDC recommends, why pools smell and sting, what overexposure looks like, how to drain a chlorinated pool safely and how to run a pool on less chlorine.
1. What does chlorine do in a pool?
Chlorine is added to pool water to kill germs. CDC’s guidance on preventing swimming-related illnesses (2025) says chlorine kills or inactivates most germs in properly treated water within minutes.
Chlorine does not work instantly on every germ. CDC’s home pool and hot tub water treatment guidance (2024) lists these disinfection times at the chlorine level and pH CDC recommends, in water without a chlorine stabilizer:
- E. coli O157:H7 (a bacterium): less than 1 minute
- Hepatitis A (a virus): about 16 minutes
- Giardia (a parasite): about 45 minutes
- Cryptosporidium (a parasite): about 15,300 minutes, or 10.6 days
CDC’s prevention guidance adds that Crypto can survive for more than 7 days in properly chlorinated water, so keeping it out of the pool matters as much as the chlorine level. Our guide to avoiding Crypto in swimming pools explains how it spreads and how to prevent it.
2. What chlorine level should a home pool have?
CDC recommends a free chlorine level of at least 1 ppm in pools and at least 3 ppm in hot tubs, with a pH of 7.0 to 7.8, in its home pool and hot tub guidance (2024). CDC’s guidelines for keeping a pool safe and healthy (2025) give 1 to 4 ppm as the typical range for chlorine.
pH matters as much as the chlorine reading. CDC says chlorine is less effective at killing germs when the pH is too high or too low. Test the water regularly, follow the product label and follow your local code if it sets different numbers. Our guide to how much chlorine to add to a pool walks through the dosing math.
3. Why does a chlorinated pool smell like chlorine?
A strong “chlorine” smell at a pool usually comes from chloramines. CDC’s guidance on preventing eye irritation from pool chemicals (2025) says chloramines form when chlorine combines with pee, poop, sweat, dirt, skin cells, deodorant and makeup that wash off swimmers’ bodies, and that “if you smell ‘chlorine’ at the place you swim, you are probably smelling chloramines.”
Chloramines are a type of combined chlorine that forms in the water and then off-gasses into the air above it, according to CDC’s chloramines and pool operation guidance (2025). CDC’s hot tub guidance adds that a properly chlorinated hot tub has little odor. Our posts on what causes pool chlorine smell and what chloramines are cover the fixes in more detail.
4. What causes red eyes and itchy skin after swimming?
Red, itchy eyes and skin irritation after swimming are usually caused by chloramines. CDC’s 2025 eye irritation guidance says swimmers can experience red and itchy eyes, skin irritation and rashes, and that chloramines can turn into gas and irritate the eyes and lungs.
The best prevention is keeping the dirt and sweat out of the water in the first place. CDC says rinsing off in the shower for just one minute before getting in the pool removes most of the dirt and anything else on your body. Keeping chlorine and pH in range, and shocking the pool when testing shows combined chlorine building up, also breaks down chloramines. Our pool shock guide explains how.
Pool water can also leave skin dry. The American Academy of Dermatology’s guidance on swimming and eczema says pool chemicals can dry the skin, and its summer skin care tips recommend showering right after you get out of the pool and applying a fragrance-free moisturizer within 5 minutes. Our guide to pool chlorine health risks covers the other effects.
5. What happens if you are exposed to too much chlorine?
At home, the most common serious chlorine exposures come from handling pool chemicals. CDC’s chlorine fact sheet (updated 2026) lists these symptoms of exposure to higher levels of chlorine:
- Blurred vision or eye tearing
- Burning feeling in the nose, throat, lungs and eyes
- Coughing
- Chest tightness
- Breathing problems or shortness of breath
- Nausea or vomiting
- Skin pain, redness or blisters, and frostbite from liquid chlorine
Pool chemical injuries are common. CDC’s MMWR report on pool chemical injuries (2019) estimated 13,508 U.S. emergency department visits from pool chemical injuries in 2015 to 2017, and most of the injuries happened at a home. People were most often hurt when they breathed in fumes or dust while opening containers, when chemicals were not stored away from children, or when chemicals were added just before someone got in the water.
CDC’s pool chemical safety poster says never to mix different pool chemicals, to open one container at a time and, when the label says to pre-dissolve a product, to add the chemical to water and never water to the chemical. If someone has trouble breathing after a chemical exposure, get them to fresh air and call 911. Our pool chemical safety guide covers storage and handling at home.
6. Is pool chlorine harmful to the environment?
Chlorinated pool water is harmful to fish and other aquatic life, so it should not go straight into a storm drain or stream. EPA’s guidance on safely discharging chemically treated water (2023) says treated pool water harms local water quality and is toxic to wildlife and fish, lists dechlorinating the water before discharge as an option, and notes that many communities have ordinances that limit these discharges.
Oregon DEQ’s fact sheet on disposing of chlorinated pool water (2017) says to hold the water for at least two weeks so the chlorine can dissipate, and that the water should not have any detectable chlorine before it is drained. Test the water before you drain it, and check your city’s rules on where pool water can go.
7. Can you run a pool on less chlorine?
Yes. A supplemental system lets a pool run on a lower chlorine residual. A Clear Comfort hydroxyl-based AOP system adds hydroxyl-based oxidation to the water, and pools with it typically run at 0.5 to 1.5 ppm free chlorine. A low chlorine residual is still needed, and maintenance is an annual cartridge exchange that takes approximately 1 to 5 minutes per year.
Lower chlorine still means keeping the water balanced and tested, and following your local code for the minimum level. Learn how it works on our hydroxyl-based AOP technology page, or compare options in Which Pool Sanitation System Is Right for You?
Frequently asked questions
What is a safe chlorine level for a home pool?
CDC recommends at least 1 ppm free chlorine in pools and at least 3 ppm in hot tubs, with a pH of 7.0 to 7.8. CDC gives 1 to 4 ppm as the typical range for pool chlorine; follow the product label and your local code.
Does a strong chlorine smell mean the pool has too much chlorine?
Usually it means the pool has chloramines. CDC says chloramines form when chlorine combines with sweat, pee, dirt and other things that wash off swimmers, and that a “chlorine” smell is probably chloramines.
How do I get rid of chlorine smell and red eyes from my pool?
Reduce the chloramines behind both. CDC says the “chlorine” smell and red, itchy eyes usually come from chloramines, so have everyone shower for one minute before swimming, keep free chlorine and pH in range, and shock the pool when testing shows combined chlorine building up.
Why do my eyes turn red after swimming?
Red, itchy eyes after swimming are usually caused by chloramines, which can turn into gas and irritate the eyes and lungs. CDC recommends a one-minute shower before swimming to remove most of the dirt and sweat that help form them.
How long does chlorine take to kill germs in a pool?
CDC says chlorine kills most germs in properly treated water within minutes. Some germs take much longer: Cryptosporidium can survive for more than 7 days in properly chlorinated water.
Can you drain a chlorinated pool into the street?
Usually not without dechlorinating it first. EPA says treated pool water is toxic to wildlife and fish, and Oregon DEQ says the water should have no detectable chlorine before it is drained; check your city’s rules before you drain.
Want a pool that runs on less chlorine? Explore Clear Comfort for home pools and spas.
