Hello — I shocked my pool last night around 8pm, added 56% cal hypo and some bleach, enough to bring the FC levels to 20 to 30ppm (getting rid of black algae). Brushed the pool good that evening twice. At 7am the next day (11 hours later), checked the FC levels twice taking samples from 2 different parts of the pool. FC measured 19 and 20. Brushed the pool again. Noon, brushed the pool again. Later that day (5pm) checked FC twice, water samples different parts of pool, and got 2.6ppm both times. Its hot 102 degrees and sunny, but still can’t figure out how the FC dropped so quickly? Thoughts?
Rapid decline in FC
- Thread starter r0st0q
- Start date
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- Tags
- algea chlorine chlorine drop
How are you testing ? With an approved kit, do a proper Overnight Chlorine Loss Test. Verify the FC after mixing the evening (dark) dose. If you keep your FC overnight but lose during the day, your CYA is likely low. If you lose FC overnight, it's SLAM Process time.