Good growing conditions are used not only to maximize yield but to improve potency, taste, etc. and to complete the cycle quicker.
Using proper pH is a contributing factor to all of those attributes.
Startring with water that is too acid or alkaline can block the uptake of nutrients, slowing growth and eventually potency and taste.
You can buy a simple pH test kit at most garden stores for about $10.00. It's not super-accurate but it's hella better than nothing. Growhops/hydro stores carry better digital pH testers starting at about $30.00.
And pH up and pH down are cheap.
Spend a max. of $40.00 to have improved yield taste & potency and get it quicker--worth it?
It is to me.
P.S. Tip: put water into a bucket and leave it (preferably outside) for several days before use. That lets the chlorine evaporate.
Distilled water is ok for seedlings, but it's not good for most plants, animals or people. Distilled water is water without all the minerals removed, and most living things need minerals.
Many markets in my area have water machines outside (some inside) that vend water for about 25 cents/gal.
They usually offer 2 kinds--distilled (mainly for irons and mixing up baby formula) and another kind that's called either spring or drinking water. If you want better water this is a good place to get it from.
When I lived in SoCal I hosted a campground up in the mountains that was near a spring. Since I went there every weekend I bought 10 five-gallon water bottles and would fill them up every week for my hydro garden. I was the only guy in the city I knew of that used what my chemist friend called "living water".
It was the best tasting weed if I do say so myself.