Chlorine drop pretty fast

[rdefino]

My cya was 60 and Chlorine was about 4, then we got about 4ins of rain over 2 days. I tested the water today (stop raining about 2 days ago) and my numbers are:

ph 7.8
alk 70
chl 1
cya 75

Would the 4in of rain cause the chl to drop so much and cya to go up?

thanks

[FormerBromineUser]

Hi, redefino! Good questions. Here are my thoughts:

First off, I doubt it the rain is the only reason your FC went down. Did you test and adjust during the rain? Many of us don't even though we should.

As for your CYA: I know you have a K2006. 75 is not a valid reading. If it was half way between 70 and 80, your CYA is closer to 72ish. Call it 70 then, or report as 70-80, closer to 70 or whatever. If you look at the spacing of the numbers on the testing vial, you will see that they are not evenly spaced.

Your CYA cannot rise if you don't use tabs or add stabilizer. You added stabilizer only 5 days ago. If it was granular CYA, it can take up to a full week to fully register. Therefore, the increase you see in your CYA is due to that addition.

As for your FC (you call it chlorine) I hope you raised it to match the new CYA level which for CYA of 70 would be between 6-9 ppm; never below 6. See this link and click "jump to chart" http://www.poolsolutions.com/gd/best...ine-chart.html

Your CYA may even settle higher in a few days, so retest it then and adjust your FC requirements as necessary using the chart linked above.

Lastly, in the future, please post your chlorine testing results as FC and CC. I couldn't find a recent CC reading in your posts. Thanks.

Hope all that helps. Let us know if you have more questions!

[rdefino]

Thanks for the reply.

So I needed to drain some water due to to much rain.
Latest tests are:

FC 1
CC 0
ph 7.8
alk 70
cya 50


So I just added some bleach and will see where it's at in the morning, then adjust from there to get it up to about 4. Then I'll bring the PH down a to 7.6.

How fast should I expect the FC to drop having my cya at 50?

[CarlD]

Why are you pushing for a low FC? If your CYA is 50 (and if you're still dissolving CYA it's going to go up) your suggested FC range is 3-6. That's for CYA of 30-50--and you want to go to the low end of that while on the high end of the range.

And if your CYA goes up some more, you'll be in the 60-90 range where suggested CYA i5-10.

So again, I have to wonder if you're looking to keep your FC too low.

BTW, I am in no way contradicting FBU's assessment.

[rdefino]

I wasn't sure with a range of 3-6 for Fc, if I should be in the middle with 4-5. Should I always stay closer to the high end?

thanks

[CarlD]

Personally, I prefer to, but that's me. But I do suggest that you look at your CYA range, you probably should pick the same part of the FC range. So if you're in the 60-90 CYA range, with a recommended FC of 5-10, if you're closer to 60, then an FC of 5-7 should be fine. If you're closer to 90, you may want to keep your FC in the 8-10 range.

But, if your FC is dropping by more than 1ppm overnight, you're either too low or you actually need to shock your water.

[FormerBromineUser]

Yup. I hope Carl's explanation made sense to you. He is one of my mentors and has the experience to go the distance. Trust him!

I also shoot for the high end, stuff happens... and the added insurance can pay off.

As for CYA, if you have made no additions since May 29, go ahead and retest your CYA. Then you will know the appropriate range you need for FC to keep your pool sanitary.

Once you have that new CYA value, remember to test regularly and add enough chlorine so that your FC will never fall below the lowest recommended ppm. (Keep in mind what Carl said about looking at where you are on the CYA range and adjusting your recommended FC accordingly).

I mentioned on your other thread to shoot for FC around 10% of your CYA. That's a ballpark value for normal CYA ranges.

Good luck!