Walmart and my local Food Lyon grocery store, as well as others, plus 'drug stores' all carry distilled water, which I'm use to paying 79¢ US to $1.09 for, per gallon, which is why I'm no distilling my own, at this time, but since I use distilled water for all processes, including washing film and papers using "The Ilford Method" if I begin to have a much larger volume of developing tasks, I would start my own distilling just to save space in my small darkroom, where more than han a dozen gallons of distilled water jugs present a storage issue.
By the way, if you make a distilling rig, using copper tubing, joints, etc, silver braze the connections, no silver solder, which is no even close to brazed silver strength and is a danger.
Do no forget to include a pressure release fitting as well.