Safe to Swim in High Chlorine levels


LifeTime Supporter
Aug 7, 2009
Hi all,
I have been fighting a bit of yellow algae, hence some shocking has been going on in the last two days:

FC: 24
pH: 7.6
TA: 100
CH: 290
CYA: 40
CSI: .84
Water temp: 86F, mostly on sun all day.

I have two questions, when is it time to stop shocking? and, is it safe to swim with these levels of chlorine?

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
SouthWest Alabama
You know you're done shocking when:
1. You lose 1ppm FC or less overnight.
2. You have .5ppm CC's or less.
3. Your water is clear if you don't have a FAS-DPD test kit.

It's safe to swim up to shock level for your CYA.


LifeTime Supporter
Aug 7, 2009
Thanks for the quick response!!! I have two eager little boys and I didn't want them to come out with bleached hair :shock: , they have green light to swim now!
I will monitor my FC with the FT100 test kit and hope to be done with the algae at once! I forgot to add that my CC was 0.

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
San Rafael, CA USA
The 24 ppm with 40 ppm CYA at your pH is roughly equivalent to a pool with 1.5 ppm FC and no CYA so similar to many indoor pools. Nevertheless, the high FC level means you don't want to be drinking lots of pool water so if your kids are real gulpers/drinkers then consider keeping them out. Getting a little water sipped in is no problem -- I'm talking about serious drinking which I presume is unlikely. This exposure is also presumed to be short-term since at some point hopefully soon your shocking will be over.

The EPA limit of 4 ppm FC assumes drinking around 2 quarts of water every day so at 24 ppm this would be equivalent to 1-1/3 cups of your current pool water every day for months. CYA essentially doesn't absorb through the skin so it is unlikely that the chlorine bound to the CYA (which is 93% of the FC) does either.