Quick answer
A pool water testing log is the timestamped record of manual water tests at a commercial pool. Operators test free and total chlorine (or bromine) and pH with a DPD or FAS-DPD kit before opening and throughout the day, test alkalinity, cyanuric acid and calcium hardness less often, and record every result with the time and their initials.
- Use a DPD or FAS-DPD kit for chlorine — test strips are generally not accepted as the official record.
- Test FC and pH before opening every day.
- Record the time of every test to show frequency compliance.
- Re-test and log after any corrective chemical addition.
Which tests to run and how often
| Test | Method | Common frequency |
|---|---|---|
| Free & total chlorine | DPD or FAS-DPD titration | Before opening + every 2–4 hrs |
| pH | Phenol red | Before opening + every 2–4 hrs |
| Total alkalinity | Titration | Weekly |
| Cyanuric acid | Turbidity test | Weekly to monthly (outdoor pools) |
| Calcium hardness | Titration | Monthly |
| Temperature | Thermometer | Each spa test; daily for pools |
| ORP (if controller) | Controller display | Record alongside manual test |
How to take an accurate sample
- Sample at elbow depth (about 18 in / 45 cm), away from return inlets and skimmers.
- Rinse the comparator with pool water first.
- Run the test immediately — chlorine in a sample cup dissipates quickly in sunlight.
- Check reagent expiration dates; expired DPD gives falsely low readings.
- Write the number on the log right away, with the time and your initials.
Common testing log mistakes
- Recording only the controller reading with no manual verification.
- Missing the pre-opening test on busy mornings.
- Leaving out the corrective action after an out-of-range result.
- Using the same log sheet for a pool and a spa.
- Rounding readings to "look right" instead of writing the actual value.
Frequently asked questions
Are test strips acceptable for a commercial pool log?
Most health departments require a DPD or FAS-DPD liquid or tablet kit for the official chlorine and pH record. Strips can be used for quick checks but should not replace the kit.
Where should I take a pool water sample?
At about elbow depth (18 inches), away from return jets, skimmers and chemical feed points, so the sample represents the bulk of the pool water.
What is the difference between free and total chlorine?
Free chlorine is the active disinfectant. Total chlorine is free plus combined chlorine (chloramines). Subtract free from total to get combined chlorine, which should stay below 0.4 ppm.
This page is an educational summary, not legal advice. Pool and spa codes differ by state and county and change over time — always confirm requirements with the health department that inspects your facility.