What type of water should i use to mix formula?

Tap water is fine: Unless you live in a rural area, use well water or don't like or trust your local water supply, tap water is fine and boiling is usually not necessary. Nursery water is also an unnecessary expense.

Safe, clean water: One should use safe, clean drinking water to mix formula. If there are possible germs in the water, the water can be boiled the day before, and left to cool down. If there are contaminants in the water, it should be filtered (or bottled water can be used). Some parents use fluoridated bottled water, so they don't have to give the baby supplemental Fluoride drops.

Tap water: If you are on municipal water use the water from your tap. If you are using well water make sure that your water tests clean for coliform bacteria and heavy metals.