Safe FC range for swimming

[Ray dm]

Good day all,

Can you please tell me if a safe swimming range for FC would be between 4-12ppm? Here is the reason I ask...

The pool store tells me my CYA is at 80. My (inexperienced) testing with TFT-100 shows CYA in the 35-50 range and DEFINATELY NOT 80. I shocked the pool a few weeks back to a level of about FC 36 (for 2 days) and have kept it no lower than 6 or 7. I've been using on average 1.5 bottles of 121 oz 8.25% bleach every day. I hope this is a normal rate for my pool. The water looks crystal clear. My only issue is what I believe to be metal related yellow on deep bottom end of pool (by the way, I don't have a lot of metal in the pool but it has been like this since I opened it a couple months back). I continue to brush the pool and added only 1 gallon of Natural Chemistry Instant Water Conditioner when I first opened the pool. I suspect a safe swimming FC range would be 4-12 based on the Chlorine/CYA chart. Any thoughts? Thank you.

 

[GuinnessPhish]

Anything below shock level is fine....so if it was in fact cya 35, you could swim in FC up to about 14.

 

[tim5055]

I would suggest an Overnight FC Loss Test (OCLT). I know it's a lot sunnier out in NM, but my similar sized pool consumes less than 1/2 bottle of 121 oz 8.25% bleach every day.

It just seems to be a lot of chlorine usage to me.

 

[timerguy]

Me too! A half jug was my usage last summer too. I bought 4 jugs a week or so ago--just in case-- haven't used a drop yet! I love my swg!

 

[Butterfly]

Hi Ray

Yep, an OCLT would rule in/out organics. Tonight, I suggest you take it up to SLAM FC level, based on 50 CYA.

It could just be that the CYA is closer to 35, but more testing is needed.
Have you seen the CYA test video? Link in my sig. Remember you need to perform it in the daytime with the sun at your back and the tube about waist high.

Have you tested the yellow stain with a cheap vitamin c tablet to determine if it is metals?

What did you add to the pool before the deep end stained yellow?

Do you use well water or municipal water to top-off your pool?

 

[Ray dm]

Thanks for all your comments. As I stated initially, I did bring the pool up to FC 36 (during the SLAM) for a couple days based on a CYA of 80 (and the OCLT was 1 or less overnight). I've since kept the pool at FC 7-14. The temperature here has been in the 90s for like 5 weeks. The CYA level seems the most tricky especially since it has been so hot outside. And yes, I have seen the CYA test video. I was just wondering if I could get more of an idea of my CYA level based on how much bleach I was adding to the pool daily. I'd really hate to add more stabilizer to my pool if it really is at the 80 level (highly doubtful based on my test). However, maybe it doesn't have enough since I still seem to be using a lot of bleach. I'll go ahead and rub a vitamin c tablet on the stain. The water does come from the city and is not well water. Also, the stain has been there since I opened the pool (along with some chipped pieces of tile from the waterline). I think the gallon bottle of 1 Natural Chemistry Instant Water Conditioner at the start of season only added 13.3ppm CYA to my 25K gallon pool. I hope I calculated that correctly.