I recently completed a stenner pump project and am trying to fine tune it. Every day for the past couple weeks I've been checking my chlorine level with a FAS -DPD test ( using the 25ml sample and multiply drops by .2 to be as accurate as I can) Doesn't seem to be much rhyme or reason to it, but my daily fc losses are all over the board some times as little as 1.8 ppm per day but as much as 4.4 ppm per day. My question is: Is the variation in my results normal? Should I just aim to add 3 ppm per day? btw CYA has been constant @ 36-38 during entire testing period.
erratic free chlorine loss?
- Thread starter echo
- Start date
A fair bit of variation is normal. Chlorine usage varies with the starting FC level, the amount of sunlight, and how many people are swimming. Sunlight can actually vary quite a bit without most people noticing. The idea is to tune your chlorine addition so the level the next day is still at least the minimum FC level for your CYA level.
By the by, measuring FC/CC by steps of 0.2 is not really useful and it uses up your reagents more quickly. Steps of 0.5 are more than precise enough. In a similar vein, pretending that you can read the CYA test as finely as 36-38 is just an illusion. The test should be read to the nearest mark on the view tube, or 40 in this case. In both cases there are huge amount of "noise" in the system. You should not make the mistake of treating that noise as something that should be tracked.
By the by, measuring FC/CC by steps of 0.2 is not really useful and it uses up your reagents more quickly. Steps of 0.5 are more than precise enough. In a similar vein, pretending that you can read the CYA test as finely as 36-38 is just an illusion. The test should be read to the nearest mark on the view tube, or 40 in this case. In both cases there are huge amount of "noise" in the system. You should not make the mistake of treating that noise as something that should be tracked.
Thanks for the help.. I don't intend on testing to the .2 increment daily. I just wanted to set the chlorination system up to be as accurate as I can from the start. I have the stenner pump currently set to deliver 2ppm daily (during the early evening) I test my fc level daily at usually between 430 to 530 pm. After I test I aim for FC of 5ppm. Usually need to add just a little in addition to what the pump delivers but not always. CYA I am testing weekly for now and it seems to remain stable. Is this safe to test at intervals of two weeks?
many only test CYA monthly or even a couple of times during the pool season. If you are not using any forms of solid chlorine or are adding CYA itself the reading should remain stable.