Strong Chlorine Smell and Burning Eyes? You Need More Chlorine, Not Less
You're seeing: A strong 'chlorine' smell and red, itchy, burning eyes after swimming.
That harsh smell and eye sting aren't 'too much chlorine' — they're chloramines (combined chlorine), which form when there's not enough free chlorine for the job. Test combined chlorine (CC): if it's above 0.5, SLAM to burn it off. A properly chlorinated pool barely smells at all. (If CC is fine and eyes still sting, check for low pH.)
It’s the most stubborn myth in pool care: the water reeks of “chlorine” and everyone’s eyes are red, so surely there’s too much chlorine — better ease off. It’s exactly backwards. That smell and sting mean there’s too little free chlorine.
Why the smell means too little, not too much
The harsh “chlorine” smell isn’t fresh chlorine — it’s chloramines (combined chlorine, “CC”): chlorine that has already reacted with sweat, sunscreen, oils, and other contaminants and been used up. Chloramines are what smell and what burn your eyes. They build up when there isn’t enough free chlorine to break through them.
A properly chlorinated pool barely smells like chlorine at all. A strong smell is the signal that free chlorine is losing the fight — the opposite of over-chlorinated.
Do this
- Test combined chlorine (CC) — free chlorine and total chlorine; CC is the difference. Target is 0, acceptable is 0.5 or below.
- If CC is above 0.5, add more chlorine. Run the SLAM process at the level for your CYA to burn the chloramines off — hold it until CC drops to ≤ 0.5.
- Keep free chlorine in the target range for your CYA going forward (the FC/CYA chart) so chloramines can’t rebuild.
- If CC is already ≤ 0.5 and eyes still sting, check pH. Low (acidic) water burns eyes — bring pH toward 7.6–7.8.
Not sure how high to take free chlorine? Enter your CYA and get the exact SLAM level to hold until the smell clears.
Your SLAM level to clear chloramines
A strong smell means combined chlorine. Enter your CYA to get the SLAM level to raise free chlorine to until it clears.
Straight off Trouble Free Pool's FC/CYA chart (minimum ≈ 7.5% of CYA, SLAM ≈ 40%), snapped to the nearest published row — the chart table stays the source of truth. Exact doses for your gallons: the chemical calculator. CYA way over 100? More chlorine isn't the fix — lowering CYA is.
What NOT to do
Don’t cut back on chlorine because of the smell — that lets chloramines build and makes it worse. Don’t buy a “chlorine neutralizer” or switch sanitizers to chase the smell. And don’t assume it’s “too much chlorine” — a quick CC test tells you the truth in 30 seconds.
This is the whole less-is-more idea flipped on its head: the problem isn’t excess, it’s a shortfall — and the answer is the right free-chlorine level for your CYA, not another product. To test CC accurately you’ll want a real drop-based kit (a strip won’t cut it).
Frequently asked
Why does my pool smell strongly of chlorine?
Counterintuitively, a strong chlorine smell means too little free chlorine, not too much. The smell comes from chloramines (combined chlorine) — chlorine that has already reacted with sweat, sunscreen, and other contaminants and been used up. They build up when free chlorine is too low to burn through them. A well-chlorinated pool has almost no smell. Test combined chlorine; if it's above 0.5 ppm, raise free chlorine (SLAM) to clear it.
Why do my eyes burn and turn red in the pool?
Usually chloramines (combined chlorine from under-chlorination), not 'too much chlorine.' The fix is more free chlorine to burn the chloramines off, not less. The other common cause is low pH — water that's too acidic stings eyes. Check combined chlorine first; if it's at or below 0.5 and eyes still sting, test and correct your pH toward 7.6–7.8.
Should I add less chlorine if the pool smells strong?
No — that's backwards and makes it worse. The smell is unreacted-chlorine's opposite: it's spent, combined chlorine that needs more free chlorine to break down. Backing off lets chloramines build further. Raise free chlorine to the SLAM level for your CYA until combined chlorine drops to 0.5 or below and the smell goes away.