tf100 cya test help

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czb182

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Oct 20, 2020
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North Virgina
cya_40.jpgcya_50.jpgcya_60.jpgpH_Cl_test.jpg

I have concerns over the TF100 test kit CYA test. Opening my pool for first time, 12k gallon. CYA was never added except for several chlorine tabs during opening, so I figure CYA was maybe 5 max. I measured and added 6lbs of dry CYA over the past 4 days, as I was worried about pH lowering. Testing CYA, i know its subjective, but if I didnt know I had added 6 lbs, I would say its 40, not 60. I attached pictures of 40,50,60. Black dot is still slightly visible at 50 to me. At 40 I cant see it at all. Anyone else have trouble with this? I followed instructions exactly.

As a side note, I was worried about pH, but its higher now?! one day after pool company opened pool, pH was 7.5(was winterized, they raised TA from 40 to 80, CH from 175 to 375, pH from >= 8.2 to 7.5,, and SLAM'd pool) Now 10 days later pH looks about 8.0, even after adding 6lbs dry CYA. I do have a spa spillover running 15 hours a day, just surprised.
 
That’s my point of confusion, I know the pool is around 12k gallons( took two full water trucks, 5000 gallon, plus partial of third). I know I added 6 lbs dry stabilizer. Therefore my cya must be at least 60, but it doesn’t appear that way.

Reason for pH worry is the tfp pool math calc says 6lbs with lower pH by 1.1, so I was thinking it might lower from 7.5 to 6.4, but obviously that didn’t happen : )
 
czb182 said:
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I have concerns over the TF100 test kit CYA test. Opening my pool for first time, 12k gallon. CYA was never added except for several chlorine tabs during opening, so I figure CYA was maybe 5 max. I measured and added 6lbs of dry CYA over the past 4 days, as I was worried about pH lowering. Testing CYA, i know its subjective, but if I didnt know I had added 6 lbs, I would say its 40, not 60. I attached pictures of 40,50,60. Black dot is still slightly visible at 50 to me. At 40 I cant see it at all. Anyone else have trouble with this? I followed instructions exactly.

As a side note, I was worried about pH, but its higher now?! one day after pool company opened pool, pH was 7.5(was winterized, they raised TA from 40 to 80, CH from 175 to 375, pH from >= 8.2 to 7.5,, and SLAM'd pool) Now 10 days later pH looks about 8.0, even after adding 6lbs dry CYA. I do have a spa spillover running 15 hours a day, just surprised.
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The CYA test is supposed to be a glance (and glance only) at the tube with sun behind you and tube held at waist height. IIRC the test makes use of light refraction through the solution. If you stare at the dot it probably won’t give you the correct value.
PH rises with aeration. Running the spillover 15hrs a day will be increasing ph.
 
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Don't be surprised that adding TA and having a spill-over running 24hrs will raise pH, that is exactly what should happen. Aeration will drive a lower pH up and TA down a bit, so slow/stop the spill-over to help stabilize and let the pH find its level but keep it in the 7s with MuraticAcid only.
 
czb182 said:
Will a pool store do better?
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No! Absolutely not. As long as you did the test outdoors with good sunlight at your back, you have a good baseline reading. I see it as 40, someone else as 50, but that's still close. It may still rise a bit more over the next few days, so I would just re-test over the weekend.
 
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czb182 said:
I added cya by putting sock in skimmer and letting dissolve.
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It could still be in the cartridge filter, it's best to hang/float it in socks in the pool or in front of return

czb182 said:
Anyone know of a more clear way of testing CYA?
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You can purchase a Standard Testing Solution (I think it's 50ppm CYA). It teaches you what CYA/50ppm looks like in YOUR testing procedure ;)
 
This is a response from Taylor to @Ecoke posted on TFP in 2017: CYA testing....Taylor's response.

"Hi Ed:

Your email was forwarded to me as I handle all the tech calls and emails into Taylor.

The CYA test is a turbidimetric test and, honestly, the lease "accurate" of any of the tests in your kit because everyone will interpret "when the black dot just disappears" differently--regardless of techniques and even using the same sample water! That's why there's no need to be specific when trying to get an answer. You don't need to see if you have 42 ppm CYA in a sample--you just need to make sure it's between 30-50 ppm (the industry-recommended ideal range).

With that all being said, how you do the test is dependent on the user. I've found that doing it outside with the sun on my back and the tube waist high versus "cloudy" days makes no difference. The only recommendation we make is to not face the sun directly (and that's for any test)."

The CYA's inherent testing variability is another good reason to always keep your FC levels on the north end of the ideal range for your best estimate of CYA ppm and well above the minimum.
 
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For what it's worth I had a similar experience this year. I knew what I had and I know what I added and I know what it should have been, but a week and half later it's still reading under what I expected.
Can I ask what brand you used for CYA?
 
I think I will try adding another 15 ppm, see if it registers. I’m wondering if it’s possible cya reacts with something in pool that makes it not show up in test. Maybe not having any before, maybe some loss. Just a guess
 
I added 1.5lb (15ppm) and i can just barely see black at 60, so it seems to raised cya level accordingly. I've added 7.5lbs now, so I should have been at 75ppm. The fact that latest dose raised appropriately makes me think somehow the inital dosage got neutralized somehow by about 15ppm, if that's possible even. I'll probably just added the remaining half pound i have left now, should bring me to 65ppm or so.
 
Monitor your FC to get an idea if you are gaining ground on your daily FC loss. No need to rush raising your CYA now rather monitor your FC by testing at lowest expected point of the day, confirm your CYA again in a few days and fine tune it as needed.
 
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CYA is tough -- sometimes it goes up more than I expect and sometimes not as much. I always add a little less than is recommended to reach a level and wait about 5 days to get my level and even then think to myself to plus or minus 10 as the test is very subjective.

In the end I wouldn't worry about it too much. I know the recommendations on TFP are for higher CYA but at the end of the day its just a supporter of for your chlorine. If you test your chlorine at the beginning and end of day and are generally close to your target levels then you are probably ok. If you haven't changed your chlorine creation (i.e - increased percentage on SWG or pump run time), and no other variable has changed dramatically (i.e. - pool party) and you find you are losing more chlorine than usual then that is the best indicator that you might need more CYA (rather than an arbitrary number).
 
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