cost water chane

I wanted to document what I think are close $$$ numbers on the true cost of a 20g water change. I chose 20g bc on avg I think most ppl are around a 20g water change when done weekly, bimonthly, or monthly. TAP WATER TO RODI: Avg cost of tap water in the U.S. is around $2.50 per 1000 gal...