CYA testing

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carlscan26

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Dec 22, 2010
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I just got a new refill of R-0013 from tftestkits I also got the 50 ppm standard so I could make sure I'm doing the test correctly. With the standard I couldn't ever get closer than 55 - and that only with holding it at chest level. The color of the ground makes a big difference too - I have three different color concretes and the lighter grey one got me the closest to 50 at 55 or so.

Ok so I have an error of 5-10 maybe my eyes are going.

So then I test my pool pulling a sample from as low as I could. 2 months ago I measured it at 60 or 80 and my mom and pop pool store that I trust measured it at 60. Today I measured it at 30 or lower??? How could I possibly have lost 30 ppm? Is it possible that the rest reagent is bad? I ordered the big bottle so I could do this test multiple times to calibrate my testing process. It arrived yesterday so it's not like it's been sitting around. Could it have been damaged in travel from excessive heat?

I'm taking a sample to the pool store tomorrow but I'm stumped on this.
 
Thanks Richard. I don't know what is going on. My FC usage is all over the place today too - looks like it's slowing down and then it picks back up again. Maybe it just isn't my day for testing lol.
 
With the standard I couldn't ever get closer than 55
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The accuracy of the CYA test is plus or minus 15ppm. With practice, you can usually home it in a little better but not much.

Regardless, what you should look for is repeatability.......getting pretty close to the same thing on multiple testings.

High FC or any other parameter out of normal has no affect on the test.

The last place I would look for confirmation of accuracy would be a pool store....TRUST YOUR TEST RESULTS!

The R-0013 reagent is inert and, to my remembrance, there has never been a report of it going "bad".
 
Thanks Dave. Well that's good news then because I was reading the standard consistently at 60.

On my real pool water test I am reading 30-40 so I'm puzzled as I measured it at 70 (60 with my +10 adjustment) just a month ago. I took a same to my mom and pop pool store who I do trust - they do the turbidity test and we've been within 10 of each other the other two times I measured against them. They're not a big chain store; I've discussed BBB with them and they got it except for the adding borates for water feel and pH stability and algae guard.

Any ideas on how I lost half my CYA in 6 weeks? We have been using the pool almost daily for the last two weeks and about 3-4 for the month before that. I've topped off maybe a total of 4" most of which I think I lost to evaporation and not splash which we do have but nothing crazy. Or at least not in my mind; most of it is dripping off as we and the toys go in and out. Either way no where close to half my pool volume.

I'll be watching consumption which has been about 1 qt per day for 2 ppm. If it goes up by much then I'll be bumping the CYA up to around 50.
 

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Yeah. Big mystery. Is it possible that the poop accident could have caused this? Some bacteria GE Erato g nitrogen killing the cya? The pool smells fine and I measure 0 CCs.

I reran the test at 5:30 so not the brightest of light and I could still barely make out the dot with the tube filled to 30. It's definitely way down.

I have grass upwind and about 20 feet from the pool. They used granular fertilizer a few weeks ago. I didn't see any on the deck around the pool though. But maybe?
 
So I'm done shocking. FC is currently 15 or was at 7:30 this morning. I have the LQ off to let the FC level drop today. Is it possible to calculate approximate CYA based on FC drop over x hours with full sun? Or are there too many other variables I'm not considering?
 
carlscan26 said:
I have grass upwind and about 20 feet from the pool. They used granular fertilizer a few weeks ago. I didn't see any on the deck around the pool though. But maybe?
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I wonder about this too. My friend's pool had 0 CYA and has been hit by granular fertilizer, from the pellet sized iron stains on the steps. That would be heavy nitrogen from urea probably, plus phosphates and potassium and then some iron and other minor metals in mix.
 
So I said earlier that my CYA was close to 30 - I remeasured yesterday before adding CYA and filled it to the top so it was less than 30. So I added a gallon on liquid CYA (I didn't want to wait a week or have a sock hanging in the pool with how much use it's been getting and will get this weekend). Anyway so now today I'm reading it at 35. Consistently so I'm happy about that!

Is the test more accurate at lower cya levels? It would seem to be given that the gradations spread out more as you go lower? Based on this assumption I'm going to adjust my offset down from +10 to maybe a 5. So I'm at 30 plus then the accuracy of the test puts me at 15-45?

What do you guys recommend for a pool with full sun from 9 to 4 and partial until 6? Should I go for 40?
 

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