Chlorine Disappears

[Reg]

Cannot get chlorine to stay in pool

Put in 5 lbs of Bioguard 99% - next day 0 chlorine

Put in 3 bags of burnout – same thing

Salt generator is working, but no chlorine

Stabilizer is OK

Salt is OK – maybe a bit high – can’t get a reliable measurement

Put in Phosfree

Put in hardness additive

Something is causing chlorine to burn out very quickly

Any idea? I’ve been to 2 pool stores for testing and did everything they suggested

Pool is clear and bright; was getting black algae so I treated for that; better now

[chem geek]

"OK" means nothing as pool store testing is notoriously wrong a lot of the time and they often think a CYA of 200 ppm is "OK". Please get your own good test kit -- either the Taylor K-2006 or the TF-100 with the latter kit having more volume of reagents so is comparably priced per test.

At what point in time did the chlorine reading start to get to zero? Was this upon spring opening? Or was it right after a black algae treatment? If the former, then you could have ammonia in the pool from bacterial conversion of Cyanuric Acid (CYA) to ammonia. If the latter, then the product you used could consume chlorine for a while so you should shock with chlorine -- not just a one-time addition but keep adding chlorine until it registers.

Note that a DPD chlorine test kit (one that shows varying intensity of pink/red) will bleach out above 10 ppm making you think you have no chlorine when you have a lot. An inexpensive OTO chlorine test kit (one that shows varying intensity of yellow) or the high-quality FAS-DPD chlorine test kit (where you count the drops until pink turns clear) won't bleach out.

You can read the Pool School to learn more about how to maintain your pool.