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**HELP!** I'm at my wit's end here. My Hayward AquaRite system keeps failing the overnight chlorine loss test (OCLT) in my gunite pool. The water looks crystal clear, but green algae keeps creeping back within days! I'm in Arizona, so it's hot and sunny, but I'm running the pump 10+ hours a day. Between this and the baby waking up every two hours, I'm getting ZERO sleep. Has anyone else dealt with this? Do I need to replace the whole chlorinator cell? I just shocked it again yesterday, but I'm scared it won't hold.

Whoa, that sounds rough, FloatFreak42. I feel you on the budget front—I'm a student and pool stuff gets expensive fast. Before you drop cash on a new cell, have you checked the basics? My Hayward system acted up last summer, and it turned out the salt level was too high (over 4000 ppm). The manual says 2700-3400 ppm for optimal performance. Also, what's your CYA (stabilizer) level? If it's too low in that Arizona sun, the chlorine burns off too fast, and if it's too high, it locks up the chlorine. A $20 test kit could save you hundreds.

Fascinating problem! As a science enthusiast, I'd approach this systematically. The OCLT failure indicates something is consuming chlorine overnight when photosynthesis isn't a factor. That points to **organic contaminants** (like algae spores or bacteria) or **inorganic oxidants** (like ammonia). Clear water doesn't rule out a nascent biofilm on your gunite surface. Have you inspected the pool thoroughly? Brush all surfaces—walls, floor, steps, behind lights—and check for slimy spots. Also, test for combined chloramines (CC); if CC > 0.5 ppm, you need to shock to breakpoint. What are your exact test results (FC, CC, pH, TA, CH, CYA, salt)? Data is key!

Thanks, both! @CurrentCaptain: Salt is at 3200 ppm (I checked last week), and CYA is around 50 ppm—I used test strips, so maybe not perfect. @FilterFan: I brushed the pool yesterday before shocking, but I'll do it again more carefully tonight. No slime that I saw, but I'm so tired I might have missed it. Test results from strips: FC ~1 ppm (low, I know!), CC ~0, pH 7.6, TA 100, CH 350, CYA 50. The chlorinator is set to 80% output. Could it be the cell is just old and not producing enough? It's 3 years old.

3 years isn't ancient for a cell in Arizona—mine lasted 4 before I replaced it. But if FC is only 1 ppm with the chlorinator at 80%, that's a red flag. First, clean the cell with a mild acid solution (1:4 muriatic acid to water) to remove scale buildup—mineral deposits from hard water can kill production. It's cheap and easy. Also, test strips can be off; consider a Taylor K-2006 test kit for more accuracy (it's pricey but worth it long-term). If cleaning doesn't boost FC, check the cell's lifespan indicator on the AquaRite display or inspect for wear. Maybe borrow a friend's cell to test before buying?

Great points, CurrentCaptain! To add: FloatFreak42, your CYA of 50 ppm is in range, but with your low FC, you're below the recommended minimum FC for that CYA level (around 4 ppm per the Langelier Index for algae prevention). The chlorinator might be struggling to keep up due to high demand. I suspect a **persistent algae bloom** that's not visible yet. Since you're in Phoenix with high temps, algae metabolism accelerates. Perform a **SLAM (Shock Level And Maintain)** process: raise FC to shock level (20 ppm for CYA 50) and hold it there until you pass OCLT (<1 ppm loss) AND CC ≤ 0.5 ppm. Brush daily during this. Monitor with a reliable test kit—strips won't cut it for SLAM. This oxidizes organics thoroughly.

Okay, I'm taking notes! I'll clean the cell this afternoon—I have some muriatic acid leftover from pool opening. Then I'll run to the store for a better test kit and start SLAMing tonight if FC is still low. FilterFan, how long should I SLAM for? Days? And CurrentCaptain, thanks for the tip on borrowing a cell; my neighbor has the same system, so I'll ask. Pray for me—and my sleep schedule! I'll update tomorrow. Really appreciate the help; this forum is a lifesaver.