Safe to swim w/ FC > 10ppm?

dchan

Member
Aug 13, 2010
12
San Jose, CA
First time owning a pool this year, and it's been very educational! Thank you TFP Pool School!

Short story:
Do I understand this chart correctly... if the CYA level is 90 or above for a non-SWG pool, it's safe to swim with FC at 10ppm?
pool-school/chlorine_cya_chart_shock

Long story:
Made the rookie mistake of using nothing but Trichlor tabs for the first 6 months. Over time, algae kept blooming and became harder to kill. After going to Pool School, I learned it was due to increasing CYA levels. I stopped using the tabs and switched to bleach. I elevated the FC > 10ppm for about week and finally got rid of the algae. Water is a nice clear blue now.

I have not added any chlorine since the last shock treatment on 8/16. The pool gets a lot of sun during the day and it has been very warm and sunny here in San Jose CA. I do have a clear solar blanket on the water (don't know if that affects FC). But I'm surprised the FC has remained high for so long. I confess that I did not have a good test kit during the shock treatment, so I suspect I went overboard with the bleach / Cal Hypo to eliminate the algae.

I just received my TF-100 XL kit today, but it was too dark for an accurate test. Instead I did a quick check with strips:
TC 10 (strip cant test above 10)
FC 10 (strip cant test above 10)
TA 80
PH 6.6
TH 500

My CYA is somewhere between 50 and 90 based on two tests from two local pool shops. I'll get my own reading tomorrow with the TF-100 kit.

So, if my CYA is near 90, is it safe to swim with FC at 10 (assuming I increase my PH to the proper levels)?
 

Shane1

LifeTime Supporter
Apr 29, 2010
621
Buckeye, AZ 85326
Welcome to the site. You will not have any issues swimming in your water. Post up a full set of test results ASAP so the experts here can get you 100% dialed in.
 

dmanb2b

TFP Expert
LifeTime Supporter
Apr 4, 2009
3,734
NY
If CYA is truly 90, then yes swimming in water with FC of 10-35 would be considered safe. Post the results with the TF100 1st so we can make sure you #'s are accurate. PH at 6.6 is too low.

Welcome to TFP :wave:
 

dchan

Member
Aug 13, 2010
12
San Jose, CA
Here are the results from the TF-100 kit:
FC 9.5
CC 1
TC 10.5
PH 7.2
TA 90
CH 530
CYA 50

FC of 9.5 is a bit high for CYA of 50, but is well below recommended shock level of 20. Should be OK to swim, right?

I welcome any and all feedback.

Thanks!
 

dmanb2b

TFP Expert
LifeTime Supporter
Apr 4, 2009
3,734
NY
Ch is kind of high, but that's OK as long as you keep PH below 7.8 and that seems to be fine.

My concern is not your FC #, that's fine for swimming with CYA at 50 but the CC of 1 is not. Perform the overnight FC loss test to confirm, but you'll need to shock to get the CC down to 0.5 or less.
 

dchan

Member
Aug 13, 2010
12
San Jose, CA
High CH probably due to the Cal Hypo shock. I'll stick w/ bleach for now.

OK, I'll check out my overnight FC loss and get the CC down.

Thanks for your help.
 

dchan

Member
Aug 13, 2010
12
San Jose, CA
Overnight Test:
FC night 8, morning 7.25
CC night 0.5, morning 0.25

I tested twice in the morning and averaged the two, which is why I have the ".25" granularity. Looks like the pool is OK... now if only the weather would warm up again.

Thanks everyone!
 
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