Trichlor and automation

This is a letter your editor wrote, about 8 years ago, to a contractor about his interest in using a tri-chlor erosion feeder to treat a busy, automated public pool. The study referenced in the last paragraph is on line here in Tech Articles, called Cyanurics, Benefactor or Bomb.  In the letter below I had to blow my horn a bit in the first paragraph to make sure he knew I meant business and had the background. Feel free to skip to paragraph 2…

Dear Sir,

At your request, I am responding with information and opinion regarding cyanuric acid's devastating effects on ORP instrumentation, specifically regarding trichloroisocyanurates used in the public-pool setting. I feel qualified to offer this opinion as I am a long-time institutional swimming-pool consultant focusing on operator training, renovations, chemical analysis and automation. I am a graduate electrical engineer, having served the pool industry as a systems and automation designer and water-treatment-system consultant for twenty five years. I have been on committees for code writing and approval in California, Texas, Nevada, Oregon and elsewhere, and served on the NSPI/American National Standards Institute Pool-Code-Writing Committee working on the new U.S. code. I am founder and executive director of the Professional Pool Operators of America. I wrote the textbook and the curriculum for the National Recreation and Parks Association's Aquatic Facility Operator training course. My specialty remains pool-water treatment.

First, let me say that the choice of "Tri-chlor" as a sanitizer is wholly inappropriate for any public swimming pool. The accumulation of cyanuric acid becomes debilitating to the oxidation/reduction potential (ORP) necessary for maintenance of water clarity and, ultimately, sanitation. As all swimming-pool automation devices measure the qualitative resultant of the presence of chlorine or bromine residuals, NOT the quantitative (parts-per-million) values read by test kits, the detracting effect of accumulating cyanuric acid has consequential, unacceptably depressing results on the ORP.

The Strantrol System 5 controller is among the best, most consistent and reliable in the industry. One of these systems could, in fact, function adequately in the presence of cyanuric acid; however the variable and rising residuals make constant attention and calibration required. An untrained operator would have little chance of making any brand of controller function satisfactorily under such conditions. The machine feeds enough sanitizer to achieve a chosen and necessary ORP; it may take very high residuals to do so in the presence of CYA!

I have included a study, presented to the National Symposium of Pool Water Chemistry in Los Angeles, 1998, which supports the critical argument against CYA in the high-load public environment. Please read this work and pass it on as necessary. I hope you have acquired an Aquatic Facility Operator manual, in which you will find a summary of this information in Chaper 13.

I hope this helps.

Kent G Williams, Aquatic Consultant
Executive Director, Professional Pool Operators of America

                                                              ~ kw            

© 2007 Professional Pool Operators of America