Quote Originally Posted by mary jo View Post
I've had dozens of (mostly) girls in the pool with very health-conscious mom's who indeed slather and spray them right before they swim…even tho I tell them repeatedly it's just going to come off in the water. I've never had anything black before. Is it the high FC levels "leeching" stuff out?
Dozens of girls, heavily coated with suntan goo, would DEFINITELY create a higher than expected chlorine load on a small home pool.

@BigDave: Any remaining ammonia would show up as CC's. Ammonia reacts VERY quickly with chlorine, so it's not likely that that is still an issue, though it may have been one before.

On the other hand, most IN-GROUND pools are very lightly used. An IG pool with lots of coated girls will have a chlorine demand that is a MULTIPLE of the typical of the 1 - 2 ppm per day.

@mary jo: If you have more than 1 - 2 girls at the pool at one time, and they stay longer than 1 hour at a time at the pool, there's a high chance they are peeing in the pool, too. If any of them are competiive swimmers, that chance approaches 100%: virtually all USS (year round) swimmers, middle school and up, routinely pee in the pool.

This is not a health risk -- urine is normally sterile -- and on well chlorinated outdoor pools exposed to full sun, it's not even a chemical problem, because chlorine + UV quickly break down the chemicals in urine. But it WILL produce a major increase in chlorine usage.