Pool Smells Like Chlorine? It's Chloramines: How to Fix

Combined chlorine = total − free

Chloramines are irritating compounds that chlorine forms with sweat and urine. Subtract free chlorine from total chlorine. If the difference (combined chlorine, CC) is 0.5 ppm or more, shock the pool with the amount on your product's label.

Most drop kits and many strips give two chlorine numbers. Free chlorine (FC) is the part still available to sanitize. Total chlorine (TC) is free chlorine plus chlorine that has already reacted with nitrogen compounds. The difference is combined chlorine (CC), mostly chloramines. Enter both readings above. The calculator does the subtraction and tells you if you need to shock. The free vs total chlorine guide explains the test itself.

Test and read the total chlorine color right away. Taylor's instructions say to match it immediately. If you used non-chlorine shock (potassium monopersulfate, MPS) recently, test before the next MPS dose or the next morning: leftover MPS shows up as combined chlorine in the standard DPD test and makes CC look higher than it is.

Why the smell means chloramines

The CDC says it plainly: if you smell "chlorine" where you swim, you're probably smelling chloramines. They form when chlorine combines with what swimmers bring in: urine, sweat, skin cells, and cosmetics. Chloramines turn into gas above the water, which is why the smell is strongest at an indoor pool or right at the surface on a still day. Water with enough free chlorine and little combined chlorine has very little smell.

Chloramines are also weak sanitizers, so a smelly pool can be under-sanitized even when total chlorine looks fine. PHTA treats combined chlorine that won't fall below 0.4 ppm as a sign of degraded water. Our calculators flag anything at 0.5 ppm or above.

How to fix: shock the pool

The fix is a shock: enough chlorine at once to break the chloramines down (pool pros call this breakpoint chlorination). How much depends on your product, so use the amount on its label. Use only a product labeled for shocking pools. Labels usually state the amount per 10,000 gallons. For a 15,000-gallon pool, use 1.5 times that amount. Then:

add chlorine in the evening so sunlight doesn't destroy part of it;
run the pump and retest FC and CC the next day;
if CC is still 0.5 ppm or more, repeat as the label directs, and if the smell hasn't cleared after a few days, call a pool professional;
don't swim until FC is at or below the swim limit on your product's label, often 4 ppm.

Indoors, open doors or run ventilation during treatment: chloramine gas collects in the air above the water.

Red eyes and itchy skin: pH too

Stinging eyes have two usual causes, and they're easy to tell apart with a test:

Chloramines (CC 0.5 ppm or more). The CDC lists red, itchy eyes, skin irritation, and rashes among their effects.
pH out of range. Taylor's trouble chart lists improper pH as a cause of skin and eye irritation and recommends 7.2–7.8. Our everyday target is 7.4–7.6. See pH levels.

Very high free chlorine can irritate too. Taylor links it to eye irritation and bleached hair and swimsuits. If FC is well above your target, see what to do when chlorine is too high.

Green hair: copper, not chlorine

Hair turns green from dissolved copper, not from chlorine. Chlorine does play a part: it roughens the hair surface, which then takes up copper more easily. Light, bleached, or sun-damaged hair shows it most. Copper usually comes from copper-based algaecides, mineral ionizers, or copper heater parts corroded by low pH. To prevent green hair:

test for copper, and keep pH from dropping below 7.2;
switch away from copper algaecides if you use them;
wet hair with tap water before swimming and rinse right after, or wear a cap.

The same copper can stain plaster and turn clear water green after a shock. See metal stains and discoloration.

Prevent it

Shower before swimming. The CDC recommends it. Less sweat and cosmetics in the water means fewer chloramines.
Take bathroom breaks. Urine is a main source of the nitrogen that forms chloramines.
Keep FC at or above the minimum for your CYA every day, especially after heavy use. See the chlorine target chart.
Test total chlorine once a week, not only free chlorine, so you notice if CC starts to rise.
Let sunlight in. Outdoor pools get help from the sun's UV light. Covered or indoor pools need more attention.

FAQ

What causes chloramines in pools?

Chlorine reacting with nitrogen compounds from swimmers, mainly urine and sweat, plus dirt and cosmetics. They build up fastest in pools with heavy use and too little free chlorine.

How to get rid of chloramines in a pool?

Shock the pool with a product labeled for shocking, using the amount on its label. Retest the next day, and if combined chlorine is still 0.5 ppm or more, repeat as the label directs.

Can pool chlorine make you itchy?

Yes, mostly through chloramines, which the CDC links to skin irritation and rashes. Very high free chlorine and pH outside 7.2–7.8 can also irritate. Test FC, total chlorine, and pH to find which one it is.

What causes pool water to turn hair green?

Copper dissolved in the water, often from copper algaecides, ionizers, or corroded copper equipment. Chlorine damages the hair surface so it absorbs copper more easily, but chlorine alone doesn't color hair green.

Sources

CDC, Preventing eye irritation from pool chemicals: cdc.gov
Taylor Technologies, K-1005 instruction card (TC − FC = CC, trouble chart): PDF
AQUA Tech Notes, Potassium monopersulfate non-chlorine shock (MPS reads as combined chlorine): PDF
The Conversation, Why does my hair turn green from the swimming pool?: theconversation.com
CDC, Model Aquatic Health Code 2024, Annex: cdc.gov (PDF)