Just tested my effluent. I had to cut it in half with DI water twice again. So only 2ml of effluent in a 10ml hanna vial, the rest is RODI with 0 TDS. So I believe I double the result TWICE to get the answer.
Measurement was 10.9 dKh, so doubled twice that is 43.6 dKh. It was 52 dKh on October 7th. So I will check again in another week and see where it is at. If it keeps going down, maybe I need to purge it.
Accuracy of a hanna alk checker is about +/- 0.3 dKh. so if you double that twice, the accuracy of a twice diluted sample is about +/- 1.2 dKh. (if my thinking is right).
So if my measurements are good, and that accuracy is correct, then my effluent has decreased in strength by about 20% over a week.
For kicks, I will let it go another week and measure. Then I will purge it, let it settle, and see if it goes back up to 52 dKh. If so, then I will have shown that I have the purge requirement too (which would be weird because my sump is SUPER calm with zero microbubbles so the air must be getting in elsewhere, or perhaps impurities in CO2 are gathering in reactor).
If that is the case, maybe Aquarium Engineering can send me a controller that has the new auto-purge function to try out.