Scope: General operating guidance only. Follow your local health department and adopted code, facility SOP (standard operating procedure), chemical label, and equipment-manufacturer instructions.
Step 1 / check the numbers
Check total and free chlorine first
- Take total- and free-chlorine samples at the same sample point and close together in time. Follow the method’s timing.
- Check the kit or meter. Look at reagent condition, sample size, mixing, read time, and units. Do not subtract results from different methods unless the procedure allows it.
- Repeat a surprise result with a fresh sample. Keep the first and repeat values.
- Check the math. If total chlorine is lower than free chlorine, check the method or written entry before calling it a trend.
Keep the paired readings together
| Record together | What to check |
|---|---|
| FC, TC, and calculated CC | Show free chlorine, total chlorine, and the calculation: CC = TC − FC. |
| Same sample point and time | Use paired samples from the same body of water and close together in time. |
| Compatible method and units | Name the methods and units; do not combine incompatible results. |
| Original and repeat values | Keep the first result and any repeat visible. |
| Pool and air context | Note recent use, circulation, odor or air complaints, and relevant site conditions. |
For a useful handoff, keep the paired readings and context together. See what a digital chemical log should include.
Step 2 / inspect the pool
Why chloramines build up
Chloramines can form when chlorine reacts with nitrogen from swimmers and the pool area. Treat the reading as a prompt to inspect the whole pool.
| Signal or context | What to inspect next |
|---|---|
| Heavy use or a sudden load | Check swimmers, contamination, sweat, urine, debris, and cleaning. Compare the timing with the log. |
| Indoor odor or air complaints | Check air flow, vents, humidity, and the site’s indoor-air procedure. A water test cannot check air quality. |
| Uneven or lasting readings | Check circulation, turnover, dead spots, sample location, water features, and recent changes. |
| CC changes with pH or FC | Review pH, free chlorine, and total chlorine together. A CC number needs those readings for context. |
MAHC CC reference, not a universal rule
The 2024 fifth-edition Model Aquatic Health Code (MAHC) uses 0.4 parts per million (ppm) as an action concentration for combined chlorine. It is a guide, not a law. It does not tell you how to treat the water. Check the local health department, authority having jurisdiction (AHJ), adopted code, and site procedure.
What the data can—and cannot—tell you
A valid CC trend can show a repeat problem. Pair it with free chlorine, total chlorine, pH, pool use, circulation, and indoor-air notes. Then decide what to inspect next.
CC alone cannot show the source of nitrogen, prove ventilation is enough, prove compliance, or tell you a treatment dose. Follow the site’s response procedure and product labels.
Safety and code boundary
A threshold is only one part of the response
MAHC is voluntary guidance, not federal law. The local health department, AHJ, adopted code, site procedure, and current conditions guide escalation, closure, ventilation, and treatment. Follow product labels and chemical-handling rules.
Where automatic testing helps
Amano for pool service companies schedules liquid-reagent tests for free chlorine and combined chlorine, plus pH and total alkalinity. It normally tests twice a day, with adjustable timing. Timestamped readings can show a repeat CC pattern. An alert after a test can send your team back to the result for review.
Amano measures water chemistry. It does not measure indoor air, find the source of chloramines, or replace required manual tests and operator decisions. It adds one more reading to the log.
Sources and scope
Reviewed August 19, 2026. Educational guidance only. Follow the adopted code, AHJ direction, product labels, and site procedure.