Tech Talk: What is the Ideal Value?

Some pool-guy philosophy with a look at pH choices

The trainers at PPOA try never, never to use the word "ideal", a word that we so often see in pool-operator guides, course texts, health-department codes… even national guidelines. There is NO ideal value for anything (pH, TA, CH, T, TDS, Air temp, air exchange, humidity, length, depth, lighting levels, number of lifeguards or number of girlfriends...) outside the context of the remaining variables, conditions and influences bearing on the component in question. Absolutes are the screaming weakness in every pool manual ever printed, code enacted or course taught. Exceptions to the many standard recommendations must be considered, unusual situations and trends compensated for, and reasons to choose values inside or outside the norm examined.

Let's look at just one variable – pH. The various state codes reveal eight different ranges as follows: 7.0 to 8.0 (4 states); 7.2 to 8.2 (4 states); 7.2 to 8.0 (6 states); 7.2 to 7.8 (16 states); 7.4 to 7.8 (2 states), 7.2 to 7.6 (5 states), and by far the most lenient, Alabama, allows pH values from 6.2 to 8.0. The most restrictive state, South Dakota, demands one value only – 7.6! Ten states have no enforced value at all, leaving it up to counties or the operator himself.

Among all this absurdity, with only one state allowing values below 7, we discover that Germany, the country who virtually invented water chemistry management and remains held up as the world's benchmark maker with their "Deutche Industrie Norm (DIN) Standard, sets a range for their whole country of pH 6.5 to 7.3, with an additional, higher limit for exceptional conditions.

After all that conflicting guidance, we must make a pH choice – based on calcium hardness (its make-up-water trends, sanitizer influences, heater type and use, and calculated target value), the TA (including its trends for the same list of reasons), the operating temperature, the TDS to a very small degree, even the expected accuracy range of our diligent hand management or that of the electronic controller! Even pool leaks, backwash frequencies and other losses can have a great influence on whether or not we can adjust our lousy make up water or just go with the flow…

All of this influencing and choosing is done in the context of pervasive beliefs that "lower pH is better" (usually) for our chlorine's function, and "higher is better" (maybe) for aggressiveness management, and "mid values are better" (at least some people believe this) for bather comfort! Health guys actually pick the middle value of their respective state's code range simply to be as far away from both limits as you can get!

It appears, therefore, that one must know his or her pool, like intimately, in order to pick the numbers he can set on his controller, paint on the pumproom wall, and count on serving him well. Yes, for all variables there're well-chosen values, best values for the situation, even excellent values for your pool. But let's leave that generalizing English word ideal to the guys who teach two-hour pool seminars, write little pool-stuff pamphlets, and sell mysterious products or services guaranteed to make all our problems go away.

~ kw

The health-department data in this article are quoted from NRPA publication The Encyclopedia of Aquatic Codes & Standards, by Kevin Johnston. Expect more articles based on this fascinating book. It is available from the NRPA Aquatic Section office, 800 677-2236.

© 2002 Professional Pool Operators of America