Not sure if it's still in operation but there was a business in Teacapan that filtered and sold tap water - it was an elaborate setup with lots of equipment - customers could watch the process. I used 5 gallon gas cans (never put gas in them) because they wouldn't tip over like jerry cans do at the first turn.
Hotel ice machines use tap water, and up till a few days ago I trusted the ice they made. We're in Mazatlan currently and both the wife and I have some mild stomach problems. For the time being I'm back to purified ice.
Teacapan was an eye-opener. We had RV'd there a lot back 15 years ago. I didn't see a single RV or a US or Canadian plated vehicle while in Teacapan. The Onac/Color Marino was too far off the road to see but it sounded like they are very slow there as well. It's a shame the RV trade has dropped off so significantly.