Chlorine consumption during SLAM

[Bvacchiano]

I’m in my second day of my first SLAM. I got crystal clear water and CC at 0. Going to do the OCLT tonight. My CYA the best I can tell is 50 (pretty confident) but I’m slamming at 60 CYA level (24). Figure more is better than not enough. Anyways I’m wondering if it is common even with the crystal clear water and no CC to bump up to 24 then in an hour be down 1-2 ppm to 22-23 in the hot sun. It’s 90 here. I feel like I keep bumping back to 24 constantly or is it just at the higher CL levels it’s easier to lose a couple PPM constantly during the sunny hot day. Maybe some lurking algae? I guess I’ll know after this OCLT. On the OCLT can I just take the measurement at say 10 pm tonight and check at 7:00 am tomorrow. Not home to do right when sun went down.
Also what’s the accuracy of the TF100 chlorine test at these high CL levels??

 

[ajw22]

See what the Overnight Chlorine Loss Test says. 10PM - 7AM period will work fine.

CL level higher then shock level just lose CL faster. 20 vs. 24 should not make a big difference.

FAS/DPD CL test is accurate up to 50 ppm.

 

[Bvacchiano]

Will chlorine burn off faster in the day at higher FC levels than at lower FC levels or is it the same? Just wondering if I’m at 20 should I expect a drop to 15 or so pretty quickly with my cya at 50 than if I was at FC of 8 to start? In other words I think I’m done with the SLAM. Crystal clear water with no CC. The OCLT was kind of odd. My first reading was 22ppm. I then did a few more to verify and was getting 25 and 27 which didn’t make any sense as there’s no way I added that much LC. Anyways checked this morning and was at 22 ppm. I’m just wondering if I go home now (5 hours later) and I’m at 15 is that normal or may I have an issue? 90 deg and sunny here today.

 

[tim5055]

Chlorine does burn off faster at higher levels. The higher you are above your "minimum" the faster the burn. The minimum is protected by CYA for the most part, above that it is fair game to the UV rays of the sun.

 

[mknauss]

Your FC loss may be a bit above what would be seen at target level, but not double.

 

[Bvacchiano]

As an example I have CYA 50. If I was at 20 this morning would it be normal To go home and test and be at 15, 6 hours later?? Again 90 deg and very sunny.

 

[mknauss]

A drop of 5 ppm during the day with an elevated FC is entirely reasonable.

 

[Bvacchiano]

Is the CYA test valid during/right after a slam? Can I take a CYA test with FC at 10?

 

[JoeSelf]

Yes, not affected by higher levels of FC.