Is It Time to Ditch Trichlor? Bob Lowry Weighs In
Most pool owners love the convenience of chlorine tablets, but few see the chemistry bill that arrives later. When trichlor is the sole sanitizer, cyanuric acid accumulates every week, making chlorine slower at killing pathogens and easier on algae than you’d ever intend. The rule of thumb is simple: maintain free chlorine at about 5% of your cyanuric acid. That means 2.5 ppm FC at 50 ppm CYA, 5 ppm FC at 100 ppm CYA, and more still if CYA climbs. The trap is that trichlor adds roughly 6 ppm CYA for every 10 ppm of chlorine it contributes, so a normal pool consuming about 10 ppm FC per week can gain around 25 ppm CYA per month. As CYA rises, you chase higher chlorine just to stay even, which further raises CYA. It’s a treadmill disguised as convenience. The chemistry spiral doesn’t stop at sanitizer performance. Trichlor is acidic, with a pH around 2.8 to 3, so it pushes pH and total alkalinity down while raising CYA. High CYA complicates balance math by depressing the alkalinity readi...