You can buy depth stops to attach to drill bits to make blind holes at a certain depth. But for occasional jobs you can gauge depth by using masking tape around the bit at the right depth. Or, as shown, drill through the center of a dowel section, using the bit you need for the hole. Cut the dowel so the exposed bit will be the depth needed for the hole.
The majority of consumers rely on local utilities to produce a safe and ample supply of water. Your local water agency is responsible for sending you an annual Consumer Confidence Report that should list the source of your water, what contaminants may be in the water, and information on the safety levels of contaminants and their effects on health.