CYA test clarification

Suzanni

New member
Sep 25, 2019
4
Jacksonville, FL
Hi from a new member! Just took over testing my own pool water last month. I'm sure I'm making this CYA test reading more difficult than it should be. For an accurate reading, results are recorded in 10 ppm increments like 30 or 40, not 35, for example? So, if the water level is between those two when the dot disappears from view, the result is recorded as which?

I need to SLAM my pool today due to yellow algae appearing after heavy rains yesterday and want to make sure I raise the chlorine level adequately.

Thanks!
 

Suzanni

New member
Sep 25, 2019
4
Jacksonville, FL
Appreciate your quick response! Thanks!
Would anyone mind looking over my pool log? I hope I've attached that correctly. I'm wondering how to use the pool calculator mid slam process so it will tell me how much chlorine to add to keep it @ a slam level? Or how do i figure that on my own? I'm sure that should be obvious. :/

Pls and thank you. I'm using the 2.5 gal, 10.5% jugs from the pool store that I had already accummulated.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,741
Northern NJ
On the HOME page tap on FC. You then get a page to calculate the addition. Confirm your pool volume and CYA of 50 is correct.

You have a slider toggle for SLAM - turn it on.

Enter your FC of 10.4. Your SLAM Target FC for CYA 50 should be filled in as 20.

PoolMath says you require 234 oz or 1.8 (128 oz) jugs of 10.5% LC.

That is more then the 96 oz your log shows you added.
 

Suzanni

New member
Sep 25, 2019
4
Jacksonville, FL
My pool looks clear and blue but my chlorine went from 7.5 yesterday - 4ppm this morning. I pressure washed the pool deck area. Some of the cool deck material is chipping off and went into the pool though i tried to keep the spray going away from the pool water. Could that have added mildew into the water? Brushing indicates algae is present. Will SLAM.

As you can see from my CYA test, I'm a bit unsure of that level. I don't know why that's hard for me to read consistently. I understand it's impossible to fluctuate as my log indicates. I realize that's important when determining chlorine needed for SLAM.

Also, I have a leak in my pool. Thought we fixed that this weekend but it's down about .5" since Sat.

Thank you for any thoughts on cause of algae. I have some tall trees near the pool and thus particles/leaves entering the pool. It needs daily cleaning and after each vacuum I spray off the filter.

Suzanni
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,741
Northern NJ
Do an Overnight Chlorine Loss Test To determine if you need the SLAM Process

Your PoolMath logs show all your CYA tests are 40-50. Thats normal testing variance. We round up. If the dot disappears between 40 and 30 you call it 40. You cannot eyeball a value between the lines since the scale is logarithmic, not linear.

Don’t agonize over the CYA test. Just call it as you see it.

After reading, pour mixture back into the mixing bottle and try it again; repeated readings on the same sample will lend confidence in the result.

Read CYA Testing - Further Reading for more tips

and watch


 
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