CYA Mystery

[chem geek]

It is forever lost. The reaction pathway is shown in this link. The reaction is essentially as follows:

CYA + 4H2O --> H+ + HCO3(-) + 3NH3 + 2CO2
Cyanuric Acid + Water --> Hydrogen Ion + Bicarbonate Ion + Ammonia + Carbon Dioxide

So the net result is a lowering of pH with some release of carbon dioxide and increase of carbonates in the water (the TA remains unchanged for technical reasons I won't get into here). For every 10 ppm CYA that is decomposed, it produces around 3.3 ppm ammonia (measured as ppm Nitrogen) and would require around 30 or so ppm FC to get rid of. Fortunately, ammonia is a little volatile so some of it may outgas.

Richard