How does a water well drilling rig work? Wells are the most reliable source of pure and clean drinking water. With one in ten people worldwide lacking access to safe water, it's more important than ever to know how to drill for water with a rig. Groundwater quality and long-term groundwater supply are the essential factors to consider while drilling a water well. The digging process will require less effort if the water is close to the surface. The contractors will dig with strong drilling machines if the area has granite bedrock.