Wow, this is the first time I looked at this thread. Three pages on whether the acid/base demand tests are useful. My two cents (and that is probably generous on what its worth). I never use it on my pool. Add a little, wait add some more. But on my spa, it is quite useful, particularly the acid demand reagent. An extra tablespoon of acid can cause a drastic overshoot. I find that the test brings me very close to a desired result.