I use RO+DI water from my local vending machine and build it back. My beer quality has skyrocketed since switching away from just using tap water. At $1.50/ 5 gallons, I find it economical enough that its now just a part of my process.
The closest machine is usually "sold out" and needs service about every third time I go there, so I have to go another mile to get water from a different maching, but that at least provides me the illusion that the machines are serviced regularly

~widget