What Are Chloramines and How Do You Remove Them? A Practical Guide to Cleaner, More Comfortable Pool Water
The biggest lesson is that a strong chlorine smell usually does not mean your pool has too much effective chlorine. It often means chlorine has reacted with swimmer waste and formed irritating compounds called chloramines. Understanding that difference can help you fix burning eyes, unpleasant odors, and uncomfortable water instead of adding chemicals without a clear plan.
Chloramines are common in swimming pools, especially after heavy use, hot weather, pool parties, or periods of weak circulation. They can also become a recurring problem when water chemistry is checked inconsistently or when contaminants enter the pool faster than the sanitizer can handle them.
Quick Answer
Chloramines are compounds created when free chlorine reacts with nitrogen-containing contaminants such as sweat, urine, body oils, cosmetics, and organic debris. To remove them, test the combined chlorine level, correct the pH, improve circulation, and oxidize the contaminants through properly calculated breakpoint chlorination or another suitable oxidation method.
What Are Chloramines?
Free chlorine is the active sanitizer available to destroy germs and oxidize contaminants. When it reacts with ammonia and other nitrogen-containing material, part of that chlorine becomes combined chlorine. The compounds within combined chlorine are commonly called chloramines.
There are several stages of chloramine formation, including monochloramine, dichloramine, and trichloramine. Trichloramine is particularly volatile, meaning it can leave the water and collect in the air directly above the pool. This is one reason indoor pools with poor ventilation may produce stronger odors and more noticeable eye, nose, or throat irritation.
Chloramines are less effective sanitizers than free chlorine. A pool may therefore contain measurable total chlorine while still lacking enough active free chlorine to maintain comfortable, properly sanitized water.
Why Does a Pool Develop Chloramines?
Chloramines form when chlorine encounters contaminants introduced by swimmers, the environment, or neglected maintenance. Common contributors include sweat, urine, saliva, skin cells, lotions, sunscreen, makeup, leaves, pollen, and other organic material.
A busy pool can develop chloramines quickly because every swimmer adds a small contaminant load. Spas, attached hot tubs, tanning ledges, and shallow play areas may experience the problem more noticeably because warmer water and vigorous aeration encourage chloramine compounds to move into the air.
Low free chlorine is another common factor. When the sanitizer level falls behind the pool's demand, contaminants are only partially oxidized. Poor circulation, a clogged filter, short pump run times, and dead spots near steps or benches can allow the problem to linger even when a test taken near a return jet appears acceptable.
Signs That Chloramines May Be Building Up
The familiar sharp pool smell is one of the best-known warning signs, but it is not the only one. Pool owners may also notice:
- Burning, red, or watery eyes during or after swimming
- Dry, itchy, or irritated skin
- A harsh odor that becomes stronger when the water is disturbed
- Coughing or throat irritation near the water, especially indoors
- Water that feels uncomfortable despite appearing clear
- Free chlorine that drops rapidly after swimmers enter the pool
Clear water does not rule out chloramines. The pool may look attractive while still having a significant difference between its free chlorine and total chlorine readings.
How to Test for Combined Chlorine
Use a reliable test kit that measures both free chlorine and total chlorine. Combined chlorine is calculated with a simple subtraction:
Total chlorine - free chlorine = combined chlorine
For example, if total chlorine is 3.0 parts per million and free chlorine is 2.4 parts per million, the combined chlorine level is 0.6 parts per million. A noticeable combined chlorine reading signals that chlorine has reacted with contaminants and that corrective action may be needed.
Test away from return jets, floating dispensers, and freshly added chemicals. Water collected from those locations may not represent the chemistry throughout the pool. When symptoms appear only in a spa, shallow ledge, or poorly circulated corner, compare readings from more than one area.
How Do You Remove Chloramines?
1. Stop Adding Contaminants
Keep swimmers out while correcting the problem. Remove leaves and debris, empty skimmer baskets, and clean visible residue around the waterline. Encouraging swimmers to shower before entering can substantially reduce the sweat, cosmetics, and body oils that consume chlorine.
2. Check and Adjust the pH
Chlorine performance depends heavily on pH. Test the water before shocking and bring the pH into the appropriate operating range for your pool and sanitizer system. An excessively high pH reduces the portion of chlorine available in its most effective sanitizing form.
3. Confirm Circulation and Filtration
Run the pump long enough to distribute treatment throughout the pool. Check that return jets are moving water across steps, benches, and other low-flow areas. Clean or backwash the filter when needed, but do not assume filtration alone will eliminate dissolved chloramines. The chemical compounds must be oxidized or otherwise broken down.
4. Use Properly Calculated Breakpoint Chlorination
Breakpoint chlorination, often called superchlorination or shocking, involves raising the free chlorine high enough to oxidize the nitrogen compounds responsible for combined chlorine. A commonly used operational calculation is to raise free chlorine to approximately ten times the measured combined chlorine level.
This is not the same as blindly adding one bag of shock. The required dose depends on combined chlorine, pool volume, the active ingredient in the product, and the pool's existing chemistry. Follow the chemical manufacturer's directions, verify the pool volume, keep swimmers out, and never mix different pool chemicals together.
After treatment, circulate the water, allow volatile compounds to disperse, and retest. Do not reopen the pool until free chlorine and pH have returned to safe operating levels for the specific pool and local requirements.
5. Improve Ventilation Around Indoor Pools
Indoor pool air can hold chloramines even after the water is being corrected. Fresh air should move across the water surface toward functioning exhaust vents. Simply opening a door may help temporarily, but recurring irritation can indicate an HVAC or air-distribution issue that needs professional attention.
Common Mistakes That Keep Chloramines Coming Back
Avoid These Chloramine Traps
- Assuming a strong odor means there is too much useful chlorine
- Testing only total chlorine instead of comparing total and free chlorine
- Adding an arbitrary amount of shock without calculating the required dose
- Ignoring pH, circulation, filter condition, and swimmer load
- Using stabilized chlorine repeatedly without monitoring stabilizer levels
- Letting swimmers return before chlorine falls to an appropriate range
High cyanuric acid can complicate treatment in outdoor pools because it changes how chlorine behaves and may require a different management strategy. In saltwater pools, the chlorine generator may maintain routine sanitation but still struggle to catch up after a large party or heavy contamination event.
How to Prevent Chloramines
Prevention starts with maintaining an appropriate free chlorine residual and testing frequently enough to catch changes early. Run the circulation system consistently, maintain the filter, brush low-flow areas, and remove organic debris before it decomposes.
Ask swimmers to shower first and avoid entering the pool with heavy lotions, makeup, or excessive sunscreen residue. No one should swim while ill with diarrhea, and regular bathroom breaks are especially important for children.
Keep accurate notes after busy swim days. If combined chlorine repeatedly rises after similar events, increasing testing frequency and planning a preventive oxidation treatment may be more effective than waiting for odor and irritation to appear.
When to Call a Pool Professional
Professional help is sensible when combined chlorine remains elevated after correctly calculated treatment, swimmers experience significant breathing or eye irritation, or indoor air problems continue despite ventilation efforts. A technician can evaluate dosing, circulation, filtration, automation, chlorine demand, and less obvious contamination sources.
If chemistry problems are happening alongside unexplained water loss, check that concern separately rather than assuming the two symptoms share one cause. The Mini Bucket Test offers a simple first step that can help compare normal evaporation with possible leak-related water loss. It does not prove that a leak exists or locate one, but it may help you decide whether further investigation is worthwhile.
The Bottom Line
Chloramines are a sign that chlorine has already reacted with contaminants, not proof that the pool has an excessive amount of effective sanitizer. Test free and total chlorine, calculate combined chlorine, correct pH and circulation issues, and use a properly measured oxidation treatment when needed. With cleaner swimmer habits and consistent water testing, most residential pools can prevent the sharp odor and irritation commonly blamed on chlorine itself.