I must be doing something wrong. I am using the TF-100 test kit. I have watched the videos and tried different light conditions. The CYA level was at 20 ppm, then I added 33 oz of cya. A week later the test showed 30 ppm. I took a sample to the pool store and they says it was 60 ppm. Then I added 16 oz of cya and after two weeks later the test shows 30 ppm. I will take a sample to a couple of different stores and compare. What could I be doing wrong performing the test?
CYA Test
- Thread starter gonzo
- Start date
If the water is cold, it is best to take the sample inside and let it warm up to room temperature before doing the test. Also, be sure you provide enough time, at least 30 seconds, of mixing after adding reagent and before viewing the results. If you rush through the mixing step you can get lower than actual results.
33+16 oz of cyanuric acid granules would raise the CYA level by about 30. If it started at 20, it should be 50 right now. However, the test isn't perfect, so +-15 from there is perfectly plausible. You are a little further off than that, so something may be going wrong (like pool not the size you think it is), but you are close to plausible results.
As a general rule, it is safer to believe your own test results, and not get hung up on comparing them to pool store results. Pool stores are frequently way wildly wrong on test results, especially CYA.
33+16 oz of cyanuric acid granules would raise the CYA level by about 30. If it started at 20, it should be 50 right now. However, the test isn't perfect, so +-15 from there is perfectly plausible. You are a little further off than that, so something may be going wrong (like pool not the size you think it is), but you are close to plausible results.
As a general rule, it is safer to believe your own test results, and not get hung up on comparing them to pool store results. Pool stores are frequently way wildly wrong on test results, especially CYA.
The test itself is fairly straight forward, mix the pool water and reagent and slowly pour into the tube until the dot disappears. Ideally you should be in full sun conditions, with the sun to your back - holding the tube waist level. Now, I am always second guessing myself as to "when" the dot disappears, so I pour the mixture back into the mixing bottle and do it again, and again, and sometime again.
Pool stores do the test indoors with lower light conditions and it is easy for the dot to disappear sooner, thus a higher reading.
Just be careful not to add too much CYA.
Pool stores do the test indoors with lower light conditions and it is easy for the dot to disappear sooner, thus a higher reading.
Just be careful not to add too much CYA.
I will try again at full sun, but I suspect I will get lower readings, because I usually test at sunset.
I agree this test is difficult. I purchased the CYA "standard" to validate my readings. The Standard is supposed to be 50 ppm. However, I can clearly see the dot at the 50 mark. The dot actually disappears at 40 for me. So either I am mixing it incorrectly, have great eyesight, or the standard isn't correct. Any suggestions?
Welcome to TFP! 
Did you get the standard from TFTestkits? If so, give them a call and they can make sure your standard is OK. Some other people reported a similar problem. You might try adding some R-0007 sodium thiosulfate reagent drops (just one should be sufficient) to your water sample before adding the CYA reagent and mixing. High chlorine levels may affect the CYA test causing it to read artificially low. Also, be sure you are not in direct sunlight. Have the sun to your back with your body shading the tube held in front of you waist-high with you looking down straight into the tube.
Did you get the standard from TFTestkits? If so, give them a call and they can make sure your standard is OK. Some other people reported a similar problem. You might try adding some R-0007 sodium thiosulfate reagent drops (just one should be sufficient) to your water sample before adding the CYA reagent and mixing. High chlorine levels may affect the CYA test causing it to read artificially low. Also, be sure you are not in direct sunlight. Have the sun to your back with your body shading the tube held in front of you waist-high with you looking down straight into the tube.
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