Why does your pool smell “fishy” or like chlorine – and how to fix It
If you’ve ever wondered, “Should my pool really smell so strongly of chlorine?” — the answer is no. A well-maintained pool should have almost no smell.
A strong chemical odor is not a sign that your pool is clean. On the contrary, it usually means something in the water is off. The good news? You can fix it.
Why does your pool smell?
The smell doesn’t come from chlorine itself. It comes from chloramines — chemicals that form when chlorine reacts with any nitrogen compounds. Sweat, urine, skin, hairs… all these are nitrogen compounds which contribute to chloramines increase.
• Monochloramine: mild, builds up over time.
• Dichloramine & Trichloramine: strong-smelling, irritating, and less effective at keeping water clean.
• Monochloramine: mild, builds up over time.
• Dichloramine & Trichloramine: strong-smelling, irritating, and less effective at keeping water clean.
In short: the smell means your pool chemistry is out of balance. It’s not that there’s too much chlorine, it’s that the chlorine is fighting to neutralise contaminants that are being introduced into the water generally by the users.
How to fix the smell and AVOID contributing to It
You don’t need to dump huge amounts of chemicals. Follow these steps:
1. Test the Water: Check free chlorine, total chlorine and stabilizer (CYA). High chloramines mean you need to act.
2. Shock the Pool with non chlorine shock MPS or with chlorine shock based on CYA ratio: The amount of chlorine you need to break down chloramines depends on your stabilizer (CYA) level:
• Low CYA (<30 ppm): light shocking usually works.
• Medium CYA (30–50 ppm): Increase chlorine enough to temporarily raise free chlorine to 20–40% of your CYA.
• High CYA (>50 ppm): Chlorine is less effective, so you may need to partially drain and refill the pool to reduce CYA before shocking.
1. Test the Water: Check free chlorine, total chlorine and stabilizer (CYA). High chloramines mean you need to act.
2. Shock the Pool with non chlorine shock MPS or with chlorine shock based on CYA ratio: The amount of chlorine you need to break down chloramines depends on your stabilizer (CYA) level:
• Low CYA (<30 ppm): light shocking usually works.
• Medium CYA (30–50 ppm): Increase chlorine enough to temporarily raise free chlorine to 20–40% of your CYA.
• High CYA (>50 ppm): Chlorine is less effective, so you may need to partially drain and refill the pool to reduce CYA before shocking.
If using non chlorine shock (MPS), swimming can be resumed after 15 minutes.
Chlorine shock:
Do this in the evening, let it circulate 24–48 hours, and keep swimmers out until chlorine drops to safe levels.
3. Prevent Future Problems:
Best practice, minimising the contamination by showering and following the pool rules.
• Encourage showers before swimming.
• Skim debris daily, vacuum weekly.
• In hot climates, change 10–20% of the water a few times a year.
• Consider UV or ozone systems to reduce chlorine use.
• Enzyme cleaners can help break down oils and organic matter naturally.
If the smell doesn’t go away, it could mean algae or buildup in pipes or filter— that’s when a professional inspection helps.
Do this in the evening, let it circulate 24–48 hours, and keep swimmers out until chlorine drops to safe levels.
3. Prevent Future Problems:
Best practice, minimising the contamination by showering and following the pool rules.
• Encourage showers before swimming.
• Skim debris daily, vacuum weekly.
• In hot climates, change 10–20% of the water a few times a year.
• Consider UV or ozone systems to reduce chlorine use.
• Enzyme cleaners can help break down oils and organic matter naturally.
If the smell doesn’t go away, it could mean algae or buildup in pipes or filter— that’s when a professional inspection helps.
A smelly pool isn’t just unpleasant — it’s inefficient and potentially unhealthy. By keeping your water balanced and shocking based on your CYA level, you can enjoy a fresh, odor-free pool that’s easier on the environment and your wallet.