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 reading; to estimate carbonate alkalinity, you subtract about one-third of the CYA from total alkalinity. This web of interactions leads to time-consuming adjustments and inconsistent water. Service pros define success as stability: you return each week to small changes, not chemistry firefights. That outcome demands limiting CYA creep, keeping pH and alkalinity steady, and matching free chlorine to the CYA level. Many who switch away from trichlor-heavy programs discover their water becomes simpler to maintain and their visits faster.

Calcium hypochlorite tablets often appear as an easy replacement, but there’s a critical safety warning: never mix cal hypo with trichlor. Together, with a little water, they generate heat and gases that can detonate within minutes. Dropping cal hypo tabs into a feeder that still contains trichlor residue can blow the lid off or rupture the canister like a firecracker. If you change tablet types, purge and clean equipment thoroughly, and never combine products in floaters, feeders, or storage. Cal hypo is a strong oxidizer, sometimes a Class III, and if it ignites, it supplies its own oxygen. You can’t smother it; only copious water can control it. Treat every container and feeder with care and follow label directions without exception.

Storage matters as much as dosing. Partially sealed trichlor buckets can admit humidity, kickstarting reactions that produce chlorine gas and nitrogen trichloride. Open that lid and you can get blasted by fumes that burn lungs and eyes. Keep tablets dry, open containers briefly, and fully reseal them—even if the child-resistant lid is a hassle. Work upwind, keep your face clear of the lid, and avoid opening suspect containers indoors. The same gassing risk exists in trichlor feeders with poor flow or clogging; opening a stagnant feeder can release a concentrated plume. Respect the chemistry, and it will respect your schedule.

The bigger lesson is to design a program that preserves stability. Choose a sanitizer plan that limits CYA rise—liquid chlorine, saltwater chlorine generators, or controlled, minimal trichlor use. Test CYA regularly and set FC based on the 5% guideline. Keep pH and alkalinity in range without constant whiplash from acidic sources. When your chemistry doesn’t drift, you win back time: less troubleshooting, fewer algae callbacks, and more predictable service routes. That’s the path many pros follow after escaping the tablet trap. Once they see clear, steady water and shorter visits, they rarely look back—except to remind others why convenience can be so costly.