Depends on what your water source pH is. If it’s between 6-7 then most don’t pH adjust the water. If it’s above 7.0 or below 6.0, many people will adjust, although, there are lots of people who don’t and claim success. Sorry for being so general but this is a question that is a bit controversial and you will get different answers depending on who you ask.
I don’t use flushing agents; I’ve always just stuck to water-only and had good results.