SLAM if CYA is zero?

cholmes28

Well-known member
Jun 9, 2014
120
Marietta, GA
I used the sock in front of return jets method, which was way faster for me than the sock in skimmer method.

Yes, I meant Soda Ash, not baking soda.

I guess CYA of 50 seems like a good place to be. The advantage of 30 is that my SLAM shock FC is almost half, which keeps the SLAM cost down, but I am hearing that 50 will help chlorine last longer, than 30?

As far as pool size, my pool is pretty easy to calculate. First, it is 20'x40', it has a 4' shelf, then drops at a 45 degree angle to 8' on other side. The only part that is a bit subjective is that 3 of the sides in deep end are also angled. I divided it up into chunks, and got pretty close to the 27k the pool company said it was.
 

cholmes28

Well-known member
Jun 9, 2014
120
Marietta, GA
Realistically, it would show a lower amount not being fully dissolved. Read my comment above I added some after you replied. I would be interested to know what your test shows if you make your CYA look exactly like my picture.
I read your post, and I am confused. If I run the test again, and shoot for the dot not completely dissappearing like in your picture, that means I will be adding less test solution, which would make the reading even higher. I am good with the 50 it is now, but if I follow your method, it would for sure be at least 10 higher. I ran out of reagent, and I wont have new bottle until Thursday, but can test again then, and let you know.
 

mknauss

Mod Squad
TFP Expert
May 3, 2014
13,657
Laughlin, NV
When you do the CYA test, try this next time.

Once you have your solution ready, back to the sun, etc. Fill the vial to a line, say 80, lower the vial to your waist level and glance for the dot, you see it, add solution to the 70 line, glance, see it, repeat until you no longer see it with a glance. Then use the CYA value one step above the line you read. So if you stopped at 50, use 60 ppm CYA.

The vial is in logarithmic scale. So it is not viable to interpolate between the lines. Just use the whole numbers, such as 50, 40, 30, ....
 

cholmes28

Well-known member
Jun 9, 2014
120
Marietta, GA
It's also possible your pool is smaller then you thought. Especially if you are going by what the builder told you. ;)
So you got me thinking about pool size, so I went out and measured everything, and plan to use my geometry skills to calculate each section, but I also ran my dimensions into several online calculators that ask for length, width, deepest depth and shallowest depth, and it came out at 26,730.
 
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borjis

LifeTime Supporter
Aug 19, 2014
2,705
Pacific NW
I did dimension calculations on the water gallons and it was still off.
Actually found it much more acurate and usefull to use pool math.
I ended up testing the chlorine, then added 1 gallon of bleach (chlorine test was showing low chlorine level)
based on the test outcome AFTER adding the 1 gallon of bleach then plugging that into pool math,
it indicated my pool was more like 19,000 gallons instead of 23,000.
Also whenever I needed to add baking soda for TA or washing soda for PH poolmath gave me
the spot on amounts to add, after I had put the pool capacity at 19,000 gallons.
 

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
2,798
Damascus, MD
So you got me thinking about pool size, so I went out and measured everything, and plan to use my geometry skills to calculate each section, but I also ran my dimensions into several online calculators that ask for length, width, deepest depth and shallowest depth, and it came out at 26,730.
With a rectangle pool it's fairly easy to accurately calculate the size. Not sure why else you would be measuring too much unless you happened to hit a pocket of water where the CYA was unusually concentrated. Wait a couple days and try again. What is your water temp?

I also suggest you get the standard solution of CYA to test your testing methods.

R-7065 CYA Standard 50 ppm (2 ounces)
 
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PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
2,798
Damascus, MD
I read your post, and I am confused. If I run the test again, and shoot for the dot not completely dissappearing like in your picture, that means I will be adding less test solution, which would make the reading even higher. I am good with the 50 it is now, but if I follow your method, it would for sure be at least 10 higher. I ran out of reagent, and I wont have new bottle until Thursday, but can test again then, and let you know.
Just to emphasize testing is about accuracy. The CYA test is the test people have the most problems with.
 
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cholmes28

Well-known member
Jun 9, 2014
120
Marietta, GA
With a rectangle pool it's fairly easy to accurately calculate the size. Not sure why else you would be measuring too much unless you happened to hit a pocket of water where the CYA was unusually concentrated. Wait a couple days and try again. What is your water temp?
My water temp is pretty cold right now, it is about 55 degrees. The issue with calculating size, is that the sides for about 75% of the length are straight for 3', then they slope. So when you get to the deep end, there is a 6' square section in the middle that is 8', but beyond that on all sides, the depth gradully decreases from 8' to 3'. Hard to explain without showing a picture, but it is a common design for vinyl IG pools. When I pulled the water for the test, I pulled it from the same corner that I had the sock hanging, but that sock had been empty for at least 15 hours, so I doubt it was still concentrated there. I am going to order a standard solution of CYA to better calibrate my test, then go from there. For now, I am going to base my target shock FC on a CYA of 50.
 

splashpad

Bronze Supporter
My water temp is pretty cold right now, it is about 55 degrees. The issue with calculating size, is that the sides for about 75% of the length are straight for 3', then they slope. So when you get to the deep end, there is a 6' square section in the middle that is 8', but beyond that on all sides, the depth gradully decreases from 8' to 3'. Hard to explain without showing a picture, but it is a common design for vinyl IG pools
Something like one of these?
https://www.poolproducts.com/images/cms-images/blog/blog-bottom-contour-inground-pool-liners-1024x309.gif
 

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
2,798
Damascus, MD
Thanks, I just ordered one. Of course after reading other TFP posts about varying results using the standard solution, I am not sure what it will tell me though. We shall see what readings I get and go from there.
I think it is because some people don't want to believe that you will still be able to see the dot. The standard solution is simple. Treat it like a pool water sample, except you don't need to look at the dot until you add reagent to the 50ppm mark. Then look and this is what you will try to replicate when you test your actual pool water. You should test your pool water in the same location and lighting as the standard solution.
 

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