Clear, but no chlorine???

[BigDave]

How much bleach did you use yesterday?

[mary jo]

one jug in the morning, and about 1/3 jug that i poured into the skimmers when wiping them down again.

[PoolDoc]

Commonly, a black line around the pool water line (and the inside of the skimmer) is a combo of people goo and lotion. At pools where many of the users are what my employees used to call "slip & dippers" (slop on the oil till they were slippery, then rinse it off in the pool, then repeat) the accumulation could be heavy.

I've also seen it occur when trichlor tabs with unusually high amounts of silicone mold release (from the process that presses trichlor powder into tabs) compound were used.

Regardless, you DEFINITELY want to clean it off if you can; time + sunlight + chlorine tend to make the black mark permanent.

[mary jo]

That certainly makes sense. What I find odd (and why I mentioned it) is the timing…I've been shocking my pool for a solid week now (to 30-35 FC), with nothing/no one in the pool during this time (other than my arm to retrieve water samples) so why would a black ring of goo suddenly show up on Sunday morning? I check and empty my skimmer/baskets daily and Saturday there was no line at all.

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?

[BigDave]

@PoolDoc, I don't know if you've read through this whole thread, so here's my quick summary from post #59:
mary jo's pool has CYA of about 150ppm, CH of 750, a history of trichlor use, periods of zero measurable chlorine, and low pH. There's no visible algae, and high chlorine demand. The Nature 2 cartridge is in place but hasn't been replaced in the last two years. There is a possibility that some amount of fertilizer made it into the pool. My guesses are that some CYA may have been converted to ammonia causing chlorine demand (no bad smell so probably not); the fertilizer may be causing chlorine demand directly; or that a nascent algae bloom (possibly aided by fertilizer) is causing chlorine demand.

Since I wrote the summary, the pool has been brought and kept at 30ppm FC and has been there for some time. During the shock, the chlorine demand seems to be subsiding but still about 7-8ppm /day with a consistent 3ppm CC.

Thanks for looking in.

[mary jo]

btw: just tested again @ 12:30 FC=30 CC=2.0
should I add a jug of bleach or wait and test later this afternoon?

[CarlD]

With an FC of 30 I'd hold off on adding more chlorine.

[PoolDoc]

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.

[BigDave]

@PoolDoc: mary jo hosted a pool party before starting the shock and has had no swimmers since - sorry, I should have included that in the summary. I agree that any ammonia would show as much higher CC and smell. After over a week at 20% shock level with clear water I doubt it's algae. So... maybe the fertilizer? Maybe space aliens? Any other ideas or more importantly, course of action? Thanks again.

[mary jo]

OK- off track here but have to comment: the pee in the pool thing really grosses me out. I may have to initiate a mandatory "pee before you get in" rule (right after the "don't splash mom" rule). I already have strict rule about always, ALWAYS having a dedicated adult watching any junior swimmers in my pool. If I'm spoiling their social scene then too bad, kiddo. I heard about the public pool stats but seriously- in a private pool people do this???