Travelers always worry about this one. Water in Mexico has gotten cleaner and cleaner every year, and it's considered drinkable... but there are still good reasons to avoid serving yourself straight from the tap.

The first one is obvious. Any time you change your environment, you're vulnerable to stomach problems. Especially when you go to an area where water is harder and heavier. It can't be helped.

The second one is to do with the water distribution system. Water is purified and then sent through the underground distribution system, just like in most countries. In Mexico, the water flow is directed by the opening and shutting of valves, but it isn't kept under pressure all the time-that depends on the water source. So during low pressure times, there's no force pushing water out and keeping contaminants from entering the pipelines through little cracks from leaks. So your tap water might have stuff sneak into it.

And the third is to do with the cisterns or tinacos. These water reservoirs are mounted on the roof, and they collect water when local wells are being pumped so that the home or building has water during outages, when the wells pumps are off. Tinacos go on the roof because gravity provides water pressure. Anyway, if the cistern isn't kept clean, bacteria can grow, and that can mess with your insides.

Drink bottled water or boil your tap water. And only use ice when you're reasonably sure it was made with clean water. That said, if you drink tap water, nothing too bad is likely to happen. You don't have to go Monk, just keep diarrhea medicine handy. And no, you won't get sick from showering or brushing your teeth unless you habitually gulp water when you do these things.