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Problem Solver - August 2007

Maintaining Water Balance in a Commercial Pool


PROBLEM:
We have a hard time keeping our water balanced and our sanitizer levels within the acceptable range even though we regularly monitor and add chemicals and water according to our measurements. What do you recommend?

SOLUTION:
Check your methods and equipment for measuring chemical levels and other water quality factors. If you manage your pool chemicals manually, the cause may be imprecise or subjective water quality measurements. Imprecise measurements can be due to instruments that are broken or out of calibration. Or the instrument or method may not be that accurate and precise to begin with. This can lead to errors in water balance that decrease the work value of your sanitizer. Though you may add more and more chemical to try to compensate, it will get you nowhere. The result is water that burns bathers' eyes and isn't sanitary. In automatic systems of control, the system may need to be recalibrated or components may have scaled over or failed in ways that are not obvious.

To get the most precise measurements of factors such as pH, ORP/Redox, TDS or mineral/salt concentration and temperature, use an electronic meter. Just checking these factors more closely will save you in chemicals, cost and hassle.


The sanitizer's ability to work is directly related to the pH. pH is also one of the primary factors in water corroding or scaling equipment. Unfortunately, if you use colorimetric testing methods that give results that must be subjectively determined, your pH measurement could be way off. Even if you have an automatic chemical monitor/controller on your system, you need to double-check its readings with an independent pH test. With saltwater pools, pH level goes up fast, so you need to check it more often. Use an electronic meter to get the best results. Otherwise, for consistency of interpretation, designate one individual to do pH testing. An example of a pH guideline range is 7.2 to 7.6.

To check whether or not the sanitizer is truly effective, historically, pool operators have tested for free chlorine or whatever chemical sanitizer is used. Modern aquatic facilities now use a variety of sanitizers and methods. To truly determine the total killing power of all sanitizers in the water, an electronic oxidation reduction potential (ORP)/Redox reading is required. A range of 650 to 750 mV is generally considered acceptable. Many automatic systems of control rely on ORP measurements to maintain sanitizer levels. You should monitor ORP levels manually with an independent instrument to ensure the system is functioning properly.

Saltwater systems that make chlorine by passing an electrical current through sodium chloride in water cannot make sanitizer if there isn't enough salt in the pool. You should manually measure the salt content with an independent total dissolved solids (TDS) analyzer that measures NaCl concentrations. This ensures that the system is working properly without making bathers uncomfortable. Consult your system manual for the appropriate range. The same TDS analyzer can be used to determine the TDS measurement required to precisely balance the water of any pool or spa. Beyond water balance, TDS in a freshwater pool has a profound impact on bather comfort, which is no small matter for a commercial AFO.

Lastly, keep good records of all your methods and measurements. Temperature, weather conditions and bather load can be correlated to chemical demands, making you more aware of when and where problems can crop up.


FOR MORE INFORMATION
Myron L Company:
760-438-2021
www.myronl.com


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