The spa has been in operation for almost a month, and we use it every day, usually twice a day. My wife and I usually soak for about half an hour every evening, and my wife does exercises each morning in the water. I've been learning as much as I can for the past six weeks or so. Before I really understood enough about testing, I decided to go with the DPD test kit k-1004 to conserve on funds. I then also purchased a k-1000 test kit along with CH reagents, thinking I would use the DPD and OT tests alternately, assuming I would get more reliable accuracy from the DPD test. I had been wanting to get the reagents for the FAS-DPD test for a couple of weeks so I finally ordered them this past week, and they arrived in the mail yesterday afternoon. In hindsight I should have purchased the Taylor k-2106 test kit from the beginning.
Once I had completed my first FAS-DPD test, I was very surprised by the results. I first tested with DPD getting ~3 ppm and OTO getting 2 ppm. This was done in strong sunlight, so since the values were low, I think the color matches were pretty close. Thinking that the FAS-DPD test would be somewhere in the same ballpark, I decided to do the 25 ml test for my first test. It took 28 drops giving a result of 14 ppm. I then repeated the test with 10 ml using 12 drops for 15 ppm. I don't know if the k-1004 test kit was old or fresh since I purchased it from someone through Amazon, but the k-1000 test kit should be relatively fresh since I purchased it from TFTestKits. The discrepancy seems greater than one would expect. I've read some old posts discussing the inaccuracy of the two color comparison tests, but I don't recall anyone mentioning a discrepancy this great. I couldn't run additional comparisons because I'm doing a bromine demand test today and the bromine level is too high for the color comparison tests to be useful. But if this level of discrepancy is consistent, then the color comparison tests will be useless, even as a rough guide between more infrequent FAS-DPD tests.
As far as I know, we have been having pretty good success with keeping the water balanced and sanitized. However, if the above holds true, then we have probably been soaking in fairly high concentrations of active bromine, since I have been keeping the bromine level at 4-6 ppm as best I could with the color comparison test kits. Just for background I have listed the other water parameters below.
Temp ~100 (varies 96 - 101)
pH 7.5
TA 80
CH 225
Borates ~50 ppm
Interested in any comments. Thanks, Michael
Once I had completed my first FAS-DPD test, I was very surprised by the results. I first tested with DPD getting ~3 ppm and OTO getting 2 ppm. This was done in strong sunlight, so since the values were low, I think the color matches were pretty close. Thinking that the FAS-DPD test would be somewhere in the same ballpark, I decided to do the 25 ml test for my first test. It took 28 drops giving a result of 14 ppm. I then repeated the test with 10 ml using 12 drops for 15 ppm. I don't know if the k-1004 test kit was old or fresh since I purchased it from someone through Amazon, but the k-1000 test kit should be relatively fresh since I purchased it from TFTestKits. The discrepancy seems greater than one would expect. I've read some old posts discussing the inaccuracy of the two color comparison tests, but I don't recall anyone mentioning a discrepancy this great. I couldn't run additional comparisons because I'm doing a bromine demand test today and the bromine level is too high for the color comparison tests to be useful. But if this level of discrepancy is consistent, then the color comparison tests will be useless, even as a rough guide between more infrequent FAS-DPD tests.
As far as I know, we have been having pretty good success with keeping the water balanced and sanitized. However, if the above holds true, then we have probably been soaking in fairly high concentrations of active bromine, since I have been keeping the bromine level at 4-6 ppm as best I could with the color comparison test kits. Just for background I have listed the other water parameters below.
Temp ~100 (varies 96 - 101)
pH 7.5
TA 80
CH 225
Borates ~50 ppm
Interested in any comments. Thanks, Michael