When I do my drop test, the sample doesn't turn completely red at 50 ppm, but at 60 ppm it goes bright red, so I just split the difference and call it 55. Maybe I'm not doing that correctly, but I figured it was better than under or over shooting it.
It’s unclear in the directions from Taylor, but in the Extended Test Kit directions here (which have been gathered from various sources including additional info from Taylor) the instructions are to test until there is no further color change. The last drop that causes no further color change does not count, but everything up to it does. So your TA is at least 60 right now.
Total Alkalinity - Trouble Free Pool
I know CYA is probably a moot test to run for my tub considering it is covered when not in use so the sun can't really destroy it very quickly, but I do add a small amount of hot tub chlorine powder weekly to regenerate the bromide base and take it to shock level. I know the chlorine powder will raise CYA in the tub and I monitor it to make sure it doesn't get too high and out of control.
CYA is moot when running bromine, is has no effect on bromine for buffering harshness or UV breakdown. This is actually why nobody really uses bromine pools, with the exception of some indoor pools, as unlike CYA for chlorine there’s nothing that keeps bromine from breaking down in UV.
This is also why the K-2005, the bromine test kit, does not come with a CYA test.
For my bromine test, I use the FAS-DPD powder test with the bromine reagent. I have the speed stir and in my 25ml tube, it says one drop equates to .5 ppm of bromine. I don't use the double test tube thing in the kit for that. I like my speed stir for bromine, alkalinity, and hardness.
Ah, good. Just checking. It is possible to use the FC reagent to test bromine, but you have to scale the result. If testing with the actual bromine reagent then follow those directions, as you are.
I appreciate the comments and advice. I'll keep my TA around 50 and hopefully the PH swing will slow down. When the PH gets up to around 8.0 due to aeration, should I use muriatic acid to lower it back down to 7.2 and then make sure my alkalinity is at 50, or should I just add enough muriatic acid to lower the PH down to around 7.5? I'll do my best to keep the alkalinity around 50. I know adding acid lowers the alkalinity so I'll monitor it whenever I add acid.
Usually when I get down to 50-60 ppm of TA I will target 7.5-7.6 when I add acid, instead of 7.2. A lower TA will result in lower pH rise, but a lowe pH will always result in a faster pH rise than a higher pH.
I have at times gone as low as 40 ppm TA, but that’s probably the absolute lowest you’d ever want to go. The lower the TA, the more a given amount of acid will drop the pH. Poolmath corrects for this in pH calculations pretty good, but if you do get the pH steady at a lower TA don’t forget dichlor is acidic and adding it can lower the pH.
