Cannot maintain FC levels w/ BBB

[Watermom]

The black dot should totally disappear. It is definitely the hardest test to read.

I'm not sure if you are also posting over on TFP, too, or not. TFP was created long after Pool Forum and was basically a spin-off of PF built on the ideas they learned here. (In fact, many of there original members are former members of PF.) However, if you are posting for help on both forums, it is best to choose one or the other. Though mostly similar, we don't totally give the same advice and it makes it hard for everybody if you are trying to use bits of both. Plus it makes it hard for us (and them) to help since we have no idea what advice is being given on the other forum.

Personally, I would not take my vinyl pool up to 39 or 54 unless lower shock levels wouldn't kill whatever type of algae I might have in my pool. Really high levels can bleach out liners. So, I would go with 18-25 and brush and see if that will take care of your issue.

[Slachey]

Watermom.

I am not posting on both forums, I simply did a search for calculating bleach quantities, and that came up. I will use your methods in the Best Guess Chlorine Chart. As there are "ranges" of FC on the chart for "ranges" of CYA, what normal FC range should I be in for a CYA of 90-100?

Thanks again for all of your assistance. Yours and others experience on this forum are invaluable!

[PoolDoc]

There are no absolute ranges, and the data and analysis has continued to develop since I first published the 'Best Guess" chart nearly 14 years ago. Currently, we're not completely sure what happens at very high levels of chlorine, even when the CYA is also very high. It doesn't seem to be a problem for people -- over the past week a local 200,000 country club pool I service has been at CYA=~100 ppm and FC=~25 ppm, with no complaints or problems.

But we're still not sure that a level like CYA=100 and FC=40 won't bleach suits or liners, though we're pretty sure it won't be a problem for 90+% of swimmers. We do KNOW that it's not dangerous, because bleach baths (CYA=0, FC=50 - 100 ppm) have been used by dermatologists for years to treat both adult and pediatric patients.

[Slachey]

Thanks PoolDoc. So would I be safe in a FC range of 8 - 12 for normal everyday use or would you go lower?

[PoolDoc]

With CYA=100, FC = 8 - 12 ppm would be fine.

If you were in an arid region, and using a DE filter, you could probably go lower. But in Pennsylvania, you'd be risking algae if you did so.

[Watermom]

Please don't think I was 'fussing' at you ------ I wasn't. It's just hard to mix and match advice from multiple forums. I hope that we have been able to answer your questions.

Let us know how your overnight test goes tonight.