Mustard algae therefore slam started (thanks to the recommendations given by those who replied to my last post!). I am concerned by the precision of my FAS-DPD test. I haven't added chlorine in hours and collected 3 samples and performed the FAS-DPD test all within minutes of each other:
1st sample: 36 drops=18 ppm, 2nd sample: 34 drops=17 ppm, 3rd sample:37 drops=18.5 ppm.
I have < 0.5 ppm of combined chlorine, pool is clear (has basically always been clear as the algae takes a couple days to grow even with nonshockable levels so just by scrubbing the walls daily a clear pool would be expected in this case), but I am particularly concerned regarding the third step re: < 1 ppm loss in 1 night, this seems almost impossible to measure given the variability in my readings.
Here are the things I have done to maximize precision: #1) bought a speedster, #2) adding reagents within a couple of minutes (thanks to the speedster), #3) measuring 10 ml with a syringe from a medical shop, #4) holding the dropper vertically.
I don't know how others can be getting the precision needed to measure < 1 ppm loss in 1 night. I believe from this forum there are 24 drops in 1 ml, but I am thinking there must some variability between drop sizes, even if it's 3% that would be enough to throw off the calculation.
Am I missing precision here compared to what I should be getting? If so, what should I do? If not, how can anyone measure a 1 ppm loss overnight with this variability? Thanks!
1st sample: 36 drops=18 ppm, 2nd sample: 34 drops=17 ppm, 3rd sample:37 drops=18.5 ppm.
I have < 0.5 ppm of combined chlorine, pool is clear (has basically always been clear as the algae takes a couple days to grow even with nonshockable levels so just by scrubbing the walls daily a clear pool would be expected in this case), but I am particularly concerned regarding the third step re: < 1 ppm loss in 1 night, this seems almost impossible to measure given the variability in my readings.
Here are the things I have done to maximize precision: #1) bought a speedster, #2) adding reagents within a couple of minutes (thanks to the speedster), #3) measuring 10 ml with a syringe from a medical shop, #4) holding the dropper vertically.
I don't know how others can be getting the precision needed to measure < 1 ppm loss in 1 night. I believe from this forum there are 24 drops in 1 ml, but I am thinking there must some variability between drop sizes, even if it's 3% that would be enough to throw off the calculation.
Am I missing precision here compared to what I should be getting? If so, what should I do? If not, how can anyone measure a 1 ppm loss overnight with this variability? Thanks!
