does this sound right? FC loss

[my2kidsmom]

My CYA is 90 and I've been getting my FC to 12 at dusk for the last few days. It's been sunny all day and hot with temps in the 90's. We've had people swimming every day, pretty much all day.
For the last few days, when I've checked my FC at the end of the day, it's been 7. So, does that sound "normal". I raise it to 12 and then the next evening when I check, it's dropped to 7 and then I raise it to 12 again and then the next evening, it's 7. I'm thinking that tonight, I'll go out at put in 2 jugs of bleach and then check in a couple of hours and the FC will be 12. Then, tomorrow we will swim and check at the end of the day at it will be 7.

TIA

 

[JohnT]

It's not abnormal. Your swimmer load can consume a lot of chlorine. Normal is 2-3ppm per day, but heavy use could raise it to 5ppm pretty easily. The thing to check is your loss overnight. Check it first thing in the morning and you should be pretty close to what you had the night before.

 

[SMWill42]

Your CYA is to high. You need to get it down. Read through Pool School in the upper right hand corner of any page. There is an article about cya/chlorine.

Susan

 

[my2kidsmom]

I know my CYA is too high. I have worked to get it down from closet to 200. I've been sitting with it at 90 because I wanted to swim and I'm moving out in the next couple of months.

 

[my2kidsmom]

My question is not about the CYA being too high, it's about the FC dropping from 12 to 7 from dusk to dusk (in basically 24 hours) with full sun, temp in the 90's, pretty much swimmers in the pool all day. Is this normal?

 

[duraleigh]

it's about the FC dropping from 12 to 7 from dusk to dusk (in basically 24 hours) with full sun, temp in the 90's, pretty much swimmers in the pool all day. Is this normal?

It's pretty close but maybe a little high.

If you suspect you are losing some to algae rather than bathers and sunlight, do an overnight FC loss test (see Pool School). If you lose more than 1ppm overnight, it's time to shock.

 

[RV]

I do not know if there is any such thing as normal, but it was about 3 ppmFC loss due to the sun and 1-2 drop due to the swimming and vacuum etc. for me but at 45-50 CYA and FC of 12 as starting point. It is probably too high for a 90 CYA, but again it may be normal for you and your location. If overnight loss is less than 0.5, it is likely normal in your case.

With a solar cover, the FC loss dropped to about 1 to 1.5 ppm ppm loss.

RV

 

[JasonLion]

FC lost because of swimming can be far more than 2 if there are several people in the water for hours.

Given the original description, "people swimming every day, pretty much all day", a loss of 5 seems completely normal to me. If there wasn't anyone swimming at all, the expected FC loss would be much lower.