Why Does My Pool Lose Chlorine So Fast?

Quick answer: Pools lose chlorine fast when stabilizer (cyanuric acid, or CYA) is too low, so sunlight destroys it, or when algae and organic waste use it up. Test CYA, correct it, and shock if the pool is dirty.

Common causes

• Stabilizer below about 30 ppm
• Algae or heavy bather load
• Hot, sunny weather
• Weak circulation

What to do

• Test free chlorine and stabilizer
• Add stabilizer per the label if it is low, then retest in a day or two
• Shock if the water is dirty or smells strongly
• Add chlorine in the evening so it has time to work
• If stabilizer is far above 50 ppm, chlorine works more slowly, and a partial drain and refill is the usual fix

When to call a pro

If you cannot keep chlorine steady after correcting stabilizer, ask a pro to run a full water test.