there really is no 1 answer....almost all water has to have ph adjusted with ph up or down after adding nutes..my tap is 8.0..ro water is supposed to be about 7.0
Distilled water is supposed to be 7.0 also. You can make your own pH down using acids like lemon juice, vinegar, or even sulfuric acid. pH up can be made using baking soda. You might be able to find some pH up/down at wally world if memory serves me correctly.
You should be able to get pH up/down at a store that sells fish or aquariums if you don't have or don't want to go to a hydroponics store, but a hydroponics store would be your best bet.
There is no such thing as "the correct pH" for the input water for every grow. You measure your runoff pH, which represents the interaction of your water, soil, nutes, amendments, etc. That is what your plants' root are experiencing so that is what you measure. You then adjust your water as needed to get to the correct runoff. If I get to the correct runoff pH by using 5.0 water and you get to the correct runoff pH by using 8.0 water then those are what is "correct" for each of us.
