By Marcelle Dibrell

Of all of the developments in the modern history of swimming pools, none can rival the impact of cyanuric acid on the pool service professional and on popular swimming pool use as a whole.

Prior to its introduction to the swimming pool industry in the late 1950s, it was necessary to continually add chlorine to pools to keep them sanitary, which is a lot of chlorine and a lot of money. Water was also frequently drained and replaced.

Not only did this make pool ownership both cost and maintenance prohibitive for many, but it also made the pool service technician an impractical profession – at least the way the job is carried out today.

Today’s model of servicing several dozen pool accounts that do well with once-weekly service would not be possible without the introduction of cyanuric acid to swimming pools.

Indeed, it is not overstating the point to say that cyanuric acid created the pool service industry.

That’s because in the absence of cyanuric acid, the sun’s ultraviolet rays break down chlorine at an alarming rate.

Added to water, chlorine exists in two forms: hypochlorous acid and hypochlorite ions. And while hypochlorous acid is relatively stable to UV decomposition, the hypochlorite ion (whose absorption maximum occurs from 290 nm out to about 350 nm) will be readily decomposed by sunlight.

Because of this, without cyanuric acid, after just one hour of exposure of chlorine to sunlight, 75 percent is lost to decomposition reactions. Add a little cyanuric acid, and that loss is reduced by a lot.

In the presence of 30 ppm cyanuric acid, nearly 80 percent of free chlorine remains after one hour in the sun.

Chlorine has been in use as a recreational water sanitizer since the early 1900’s when it was first used to sterilize a Brown University swimming pool. A Brown University student, John Bunker, used it to treat the University’s pool and published his 1911 chlorination experiment in the American Journal of Hygiene.

Although cyanuric acid was first synthesized by Friedrich Wöhler in 1829, (by the thermal decomposition of urea and uric acid), it wasn’t used as a chlorine stabilizer for swimming pools until much later.

According to the U.S. EPA, chlorinated isocyanurates were first registered in the U.S. in 1958 for use as disinfectants, sanitizers, algicides, and fungicides. Distributing these compounds in tablet form had already been made possible with the 1956 Olin Mathieson invention of a floating polyethylene mesh basket that could be suspended in a pool and allow chlorination tablets to dissolve.

Thus, by the early 1960s, modernday chlorination techniques had emerged, and the once-weekly pool service profession was made possible.

In this special issue of Service Industry News, we take a detailed look at cyanuric acid.