Will tap water work?

As a general rule, if you drink your tap water, your sourdough probably can, too. However, if it's chlorinated, it might not work because sourdough is supposed to be a colony of healthy bacteria, and water is chlorinated to kill bacteria. So if you have chlorinated water, consider at least starting your sourdough starter with other water such as spring water. Once you have a healthy starter established, then you can experiment by dividing your starter into two jars and using chlorinated water for one jar and spring water for the other. After you do this for a few weeks, you should be able to tell if the chlorine is hindering the sourdough at all.