Quick answer
Stop adding chlorine and test free chlorine and combined chlorine. If free chlorine is high, keep people out and let sunlight and circulation bring it down. If combined chlorine is high, the pool needs oxidation and filtration, not more maintenance tablets. Do not use a chlorine neutralizer unless a professional advises it.
What you're seeing
- A sharp chlorine or “pool” smell hangs around the water.
- Swimmers report stinging eyes, coughing or irritated skin.
- Free chlorine reads high, or combined chlorine is elevated.
- Bathing suits fade faster than expected or the water feels harsh.
What usually causes it
Cause 01
Combined chloramines
Chlorine that has reacted with sweat, urine, sunscreen and other organics becomes combined chlorine. It smells strong and disinfects poorly.
Cause 02
Too much free chlorine
Over-dosing, a stuck feeder or a miscalculated shock can leave free chlorine above the safe swimming range.
Cause 03
Poor circulation
Pockets of stale water and short pump runs let contaminants accumulate even when the test at one end looks acceptable.
Cause 04
Low CYA and strong sunlight
Unstabilized chlorine can burn off quickly, prompting repeated dosing that swings between high and low.
How to fix it, in order
Work through these steps once, with the pump running and the filter clean. Do not stack a second chemical dose before the first has circulated and you have retested.
- 01
Test FC and CC separately
A total chlorine reading hides the difference. Free chlorine is the active sanitizer; combined chlorine is the spent portion that causes the smell.
- 02
Stop adding chlorine
Turn off the feeder, remove floating tablets and do not shock until you know which number is high.
- 03
Let high free chlorine fall
Sunlight and circulation reduce free chlorine. Keep swimmers out until the reading is back in the normal range for your CYA.
- 04
Oxidize high combined chlorine
If combined chlorine is high, the pool needs a proper oxidation dose with the pump running. Follow a chlorine/CYA chart and retest before reopening.
- 05
Clean the filter and surfaces
Brushes, baskets and cartridge media can hold oils and biofilm. Clean them so the pool is not recontaminating itself.
What not to do
- Do not add more chlorine just because the pool smells; test combined chlorine first.
- Do not let anyone swim while free chlorine is above the safe range or the water is irritating.
- Do not mix chlorine with acid or other chemicals to try to neutralize it.
Keeping it from coming back
- Shower before swimming and keep babies in swim diapers to reduce chloramine load.
- Shock after heavy bather loads rather than waiting for the smell.
- Run the pump long enough to circulate all of the water.
- Keep CYA in range so chlorine is not burned off and re-dosed constantly.
When to stop and call a pro
Do not force it
Call a professional if strong fumes persist, anyone has trouble breathing, the feeder will not stop, or free chlorine stays dangerously high. For a gas heater or chemical feeder issue, use a licensed technician.
Compare local repair helpGeneral guidance for residential pools in Ontario. Chemical doses depend on pool volume and test results; follow the product label and keep gas, electrical and major shell work with licensed trades.