Chlorine loss

[mrmrshenke2005]

I recently stopped the SLAM on my pool because it past all three tests. One day after I stopped I tested the water in the evening with my TF-100 test kit.

FC 4
CC .5
CH 175
TA 90
CYA 30
PH 7.5

In the morning the FC was at 11.5 so there was a 7.5 ppm drop in 12 hours during the day. Is this amount of drop normal? I added enough liquid chlorine to get it back to a 7 then this evening it was 1.5 (about 5.5 drop in 24 hours).

I was thinking about bringing my CYA up to 40 or 50 but not sure if that will correct the amount of lost chlorine.

Any thoughts on how much loss I should expect and if the amount I am dropping is indicating a different issue?

Also, for the CYA test can you use a flashlight or does it need to be daylight or even direct sun light for the most accurate test?

 

[mknauss]

Pool School - CYA. It is best to have full sun at your back when you do the test.

You are seeing too much FC loss. Normal pools consume 2-4 ppm FC daily during the summer.

 

[demilio56]

Marty,
would you consider 2-4 ppm per day normal for no use, normal use, or heavy use? Or all of the above?

 

[mknauss]

Normal use. If you have children in the pool for extended periods, that is extraordinary use, as they tend to not get out to pee. And thus your FC loss is much higher.

 

[Demegrad9]

mrmrshenke2005, sounds similar to my situation early this season. After opening and getting up to SLAM level it seemed that I could pass OCLT but I seemed to be losing ALOT of FC during the day. I was at 30ppm CYA and I didn't want to raise it because that would just make SLAMing a little harder if it was still necessary. I guess I was just doubting myself and my testing but eventually I just went ahead and used 1 whole canister of CYA (which I think was 4lbs) to increase CYA by about 15ppm if I remember right and my daily FC loss went back to normal which is about 1ppm per day. Just fyi though, I think Marty is right 2-4ppm FC loss per day is more typical, my pool is only lightly used (i.e. by me after work each weekday and friends on weekends), has a solar cover on most of the time, and because of surrounding trees the pool doesn't get sun all day.

So in short, I can just say that going from 30 to 45ppm CYA made a big difference for me. If you're testing and getting CYA level of 30, I would suggest using Pool Math to figure out how much to add to increase CYA by 10ppm and see what your FC loss does. If that seems to help, then maybe increase all the way up to 50ppm CYA.

 

[niteshift38]

Just as Demegrad9 stated, my daily FC loss also dropped a lot when I upped my CYA from 30 (pool opening reading) to 50 or just under (made sure I could see the dot at 50, but no way at 40).

Good Luck !!!

 

[s_vidden]

Just as Demegrad9 stated, my daily FC loss also dropped a lot when I upped my CYA from 30 (pool opening reading) to 50 or just under (made sure I could see the dot at 50, but no way at 40).

Good Luck !!!

Had the same issue myself earlier this summer. In my case access rain fall diluted my CYA from 50 to less than 30. We had over 10 inches of rain fall for the month of June. As a result I was burning 7-10 ppm of FC daily. Bumped my CYA back up to 45 (rounded to 50) and back to normal 3-4 ppm loss per day. In my case I will aim to keep my CYA between 40 and 50 (round my pool math to 50).