Bob Lowry: Party-Ready Pools and Alkalinity Control

Crowded pool days can turn clear water cloudy fast, but a few smart steps before guests arrive protect clarity, comfort, and budget. Bob Lowry lays out a simple plan: raise free chlorine a few ppm, add a measured dose of non-chlorine oxidizer, and keep the circulation system running throughout the event. The surprise hero is the shower. A quick rinse removes sunscreen, deodorant, lotions, and oils that devour sanitizer in the first minutes after swimmers enter. Studies show pre-swim rinsing can cut chemical demand dramatically, which means fewer chloramines, better smell, and happier eyes. Pair that with a steady filter and you trap organics early, letting chlorine focus on disinfection instead of cleanup.

Many service techs run into a different headache: sky-high cyanuric acid from heavy trichlor use. For every 10 ppm of chlorine dosed via trichlor, about 6 ppm of cyanuric acid remains. Over weeks, that creeps upward, forcing the required free chlorine residual to rise to maintain the same level of protection. Bob’s rule of thumb without borates is 7.5 percent of CYA as a target free chlorine level. If CYA climbs 25 ppm per month, the needed free chlorine rises about 1.5 ppm monthly. Ignore that, and algae risk spikes, shock frequency goes up, and costs follow. The smarter path is to manage CYA down to a workable 50 to 60 ppm and set chlorine accordingly, reducing runaway demand and improving kill rates.

High CYA also distorts how water balance looks on paper. The saturation index should rely on carbonate alkalinity, not total alkalinity, because cyanuric acid ties up part of alkalinity. Subtract roughly one-third of the CYA reading from total alkalinity to estimate carbonate alkalinity. At CYA 200 ppm with TA 70 to 80 ppm, the adjusted value can approach zero, meaning corrosive water even if the “visible” TA seems normal. That drives etching, plaster color loss, and metal staining as surfaces dissolve and later re-precipitate. Trying to mask the problem by raising TA higher creates a new fight as pH drifts upward and acid additions push TA back down. Break the cycle by partially draining to reset CYA, then balance pH, TA, and calcium in a stable range.

Correcting extreme low pH is best done in stages. If a large vinyl pool tests near pH 5, dumping massive soda ash in one shot risks a pH spike, calcium clouding, and days of filtration to clear fallout. Bob suggests a blended approach: lift pH a bit with soda ash, build alkalinity with baking soda, and use aeration to finish the pH rise without overshooting. Point return jets up, or run a submersible to agitate the surface. CO2 off-gassing raises pH without moving alkalinity, helping you fine-tune balance while saving chemicals. When the target dose is large, add chemicals in thirds with retesting between rounds to verify pool volume assumptions and reaction progress, avoiding the whiplash of adding acid to correct an overshoot.

Filtering strategy matters during and after a party. Keep the pump on so the filter captures the load that would otherwise burden chlorine. After swimmers leave, run at least one full turnover—longer if the water looked stressed—to clear fine particulates and let sanitizer recover. If you rely on stabilized chlorine, watch CYA monthly and plan for dilution as part of routine care. When you respect the relationship between CYA, free chlorine, and carbonate alkalinity, algae control becomes predictable, plaster stays protected, and you spend less time on emergency fixes. Simple habits—pre-swim rinsing, proactive chlorine and oxidizer use, continuous circulation, and careful chemistry adjustments—turn heavy bather loads into a non-event.