There are many thing that you have to be careful of drinking when you are travelling to Bali. One of them is water.
When l was young kid, l lived in the mountain village named Kintamani. I used to drink water straight from the underground spring. For me it was no problem. But today, that under ground spring feeds houses, villas, and hotels, and it has become polluted.
Now I have to boil the water that comes from the spring to my house through my tap. Boiling the water typically kills all the bacteria. Then I keep it cold for drinking.
For travelers, it's best to drink bottled water only. Brush your teeth with bottled water. Try not to let the water from your bath or shower into your mouth. Tourists usually don't have the option of boiling their water before consuming, like I do. So please don't drink the tap water and stick to water you buy in a bottle.
I am an English Speaking, local Balinese driver and guide. I'd love to help you have a great visit to the Island of the Gods