Well there is health guidelines the well companies abide by,rural areas may let home owners have a well for a secondary water source outside the home,not sure about your area but surface water table for this purpose lies just below the glacial drift (if any) and lies on the 1st layer of clay,a 4" well with a 3/4hp submirsiple pump will put out plenty of water with a coarse screen for this purpose,drinking water they need to go beyond the 1st clay layer to insure quality/safe drinking water.Check with the city to see where your water table is and also the average depth of wells in your area.