Hi - I have only recently got my tap water analysed. Up to now I have used rule of thumb additions of Gypsum and Epsom salt. Results are very drinkable, but there's always room for improvement, so I am looking at more refined additions in my next brew. I've found a number of calculators, some of which are more intuitive than others. I liked the simple layout of your one, but it seems to require me to use some form of acid - I tried not selecting one and it wouldn't proceed. I've not used acids in brewing so far - is it possible to have an option of None?