I calculate the pool about 13k gallons, so 3 gallons of 12% would give 30 or so chlorine- very easy to bleach out some tests! try a cheap OTO test, or your own FAS-DPD test... the OTO test will turn brown, I think at high FC levels...
We really need complete tests to advise- he could have extreme ammonia build up if a lot of CYA was used before, or other issues...
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