Maintaining the water quality in any public aquatic venue is not an easy job. It takes constant, consistent vigilance and accurate documentation. Here’s a look at what you should be monitoring.
- Chlorine (disinfectant) level. Disinfectant levels should be monitored at least as frequently as indicated by the local health code; many state health codes recommend three times a day.
Heavier bather loads and other environmental factors affect levels, so the recommended frequency could be every two hours while a busy pool is in operation. The minimum chlorine level for venues not using cyanuric acid is 1.0 ppm. For venues using cyanuric acid, it’s 2.0 ppm, and for spas it’s 3.0 ppm.
- pH. Like the disinfectant level, pH should be monitored frequently, every two hours in a busy pool. While codes indicate a 7.2 to 7.8 pH level, most find a 7.4 to 7.6 pH level is best.
- Combined chlorine or chloramine levels. Aquatics facilities should monitor combined chlorine or chloramine levels at least weekly, to avoid that stinky smell that starts around 0.4 ppm or higher. Lowering the chloramine level can be accomplished through hyperchlorination.
- Total alkalinity level. Total alkalinity is the anchor for the pH level in the water. Unless you're having difficulties with your pH level, a weekly test should be adequate. Total alkalinity levels should be between 80 and 150 ppm.
- Cyanuric acid and stabilized chlorine products (for outdoor pools only). Cyanuric acid and stabilized chlorine products in a swimming pool will protect the chlorine from the sun’s rays the way sunscreen protects from sunburn. Too much cyanuric acid also can cause problems, such as making it more difficult to kill crypto or locking up the chlorine level. Be sure to monitor this level weekly so it does not exceed 50 ppm.
- Source water. Once a month, check the pH, chlorine, total alkalinity and calcium hardness levels in the source water to spot any change in levels. This is especially helpful if your water source is from the drinking water system. Quickly detecting small changes in the source water monthly can sometimes help explain a change in the pool water.
- Calcium hardness level. The calcium hardness or how hard/soft your water is should be checked monthly and should not exceed 400 ppm. The exact level is dependent on the pH and temperature of the pool water. You can calculate the correct ppm using the Langelier Saturation Index, a tool developed in the 1930s to calculate water composition.
- Total dissolved solids level. According to TheAquapedia.com, TDS is the measure of the total amount of dissolved matter in water, such as calcium, magnesium, carbonates, bicarbonates or metallic compounds.
The maximum acceptable level of TDS for pools is 1,500 ppm above the TDS level in the source water. This level should not change significantly from month to month in most pools, while warm-water therapy pools and spas might require weekly monitoring. Following these basic daily, weekly and monthly monitoring guidelines will ensure that your aquatics facility is a place everyone will enjoy.
About the Instructor
Terri Stroupe is the aquatics director of the Raleigh (N.C.) Parks & Recreation Dept., with 31 years’ experience in water safety and aquatic management. A Certified Pool Operator Instructor for 24 years, she is currently volunteering on the CDC’s Model Aquatic Health Code project with the Disinfection and Water Quality Technical Committee.