I get better beers from treating our water. Lots of the treatment out there assumes a start from RO water and that everyone's a super-taster and can tell the difference when you manipulate the chloride-sulfate ratio. I start from a variable municipal water source that's treated with chlorine. Let's see, job one is dechlorinate. If I do nothing else, I have to do that. Job 2 is making sure I have enough calcium. Mash and yeast need it, so the water should have at least 50 ppm. We are starting with 36 ppm on average here. So I need to add at least 14 ppm, which I'll likely add in the next step, controlling residual alkalinity. I have to add it as a salt and I prefer malty to hoppy, even when brewing very hoppy beers my go-to is calcium chloride. Then I work on the residual alkalinity to predict my mash pH. A mash at pH 5.4 clarifies better, converts better and makes a better beer. Again, my go-to is calcium chloride for that, simply because I like malty. If necessary, I'll add some lactic acid to bring the pH down to within a half a point of 5.4. I batch sparge so I don't bother acidifying the sparge water - it's nearly impossible to over-sparge when batch sparging. The final treatment with salts comes at bottling. I add a touch of table salt with my priming sugar to punch up the malt a bit more.
That's Nosy's quick-and-dirty water primer. The only mandatory step is dechlorination. Otherwise, as mentioned earlier, people have been adjusting recipes to water for centuries. Got hard water, brew dark beers. Our water lends itself to ambers and browns so I see a lot of them here. Very soft water lends itself to fizzy yellow beer but you can brew any with any water source, armed with knowledge and a few vials of salts and acids.