Algae keeps coming back even when your test reads “plenty of chlorine”? Here’s the missing piece: cyanuric acid quietly ties up most of your free chlorine, leaving only a small slice as active HOCl. We dig into the real chemistry behind clear water, then translate the math into one simple rule you can use on every stop. We walk through the practical percentage target that actually prevents algae: set free chlorine to 7.5% of your CYA, or drop that target to 5% when you run borates at 50 ppm. You’ll hear why pools with 150–200 ppm CYA can still turn green at 6 ppm FC, how pH shifts HOCl to weaker OCl−, and why weekly shock isn’t a strategy. If you’ve ever fought a trichlor-heavy pool through summer and wondered why “within range” fails, this conversation gives you the framework to fix it. We also unpack LSI fundamentals to predict scale and corrosion, then explain why balance on paper isn’t enough if the pool won’t stay put between visits. Targets beat broad ranges: tune alkalinity to control pH rise, maintain appropriate calcium hardness, and let borates smooth pH swings so sanitizer stays effective. By focusing on stable set points instead of chasing numbers, you protect plaster and equipment, reduce callbacks, and keep water reliably clear. • CYA binding lowers active chlorine and HOCl • The 7.5% of CYA free chlorine rule • Borates at 50 ppm reduce the FC target to 5% • High CYA pools need higher FC despite “good” tests • LSI as a prediction tool, not a cure-all • Targets for stability versus chasing ranges • Balance that holds week to week, not just on paper Are you a pool service pro looking to take your business to the next level? Join the Pool Guy Coaching Program. Get expert advice, business tips, exclusive content, and get direct support from me. Learn more at swimmingpoollearning.com The Pool Guy Podcast Show is teamed up with UPA to bring you affordable, reliable liability insurance starting at just $64 a month. Sign up with UPA today by clicking the link in the podcast description Send us a text Support the Pool Guy Podcast Show Sponsors! HASA https://bit.ly/HASA The Bottom Feeder. Save $100 with Code: DVB100 https://store.thebottomfeeder.com/ Try Skimmer FREE for 30 days: https://getskimmer.com/poolguy Get UPA Liability Insurance $64 a month! https://forms.gle/F9YoTWNQ8WnvT4QBA Pool Guy Coaching: https://bit.ly/40wFE6y Support the show Thanks for listening, and I hope you find the Podcast helpful! For other free resources to further help you: Visit my Website: https://www.swimmingpoollearning.com Watch on YouTube: https://www.youtube.com/@SPL Podcast Site: https://the-pool-guy-podcast-show.onpodium.com/ UPA General Liability Insurance Application: https://forms.gle/F9YoTWNQ8WnvT4QBA Pool Guy Coaching Group Join an exclusive network of Pool Service Technicians to access the industry’s leading commercial general liability insurance program. Protect your business. Premium is $64 per month per member (additional $40 for employees and ICs) $59 per month for Pool Guy coaching Members - join here! https://www.patreon.com/poolguycoaching Limits are $1,000,000 in occurrence and $2,000,000 in the aggregate - Per member limits [ $1,000,000 per occurrence and $4,000,000 aggregate available for $75 per month ] $50,000 in HazMat Coverage - clean up on-site or over-the-road Acid Wash Coverage - Full Limits
