If the break is outside the house (between house and street, no coverage. If the line is under the house and the line cracks/breaks/collapses, digging up the floor to get to the pipe would be covered, but you would pay of cost of the actual pipe. This would be on a deluxe policy; confirm with your agent.
Similar situation: My bathroom tub drain line cracked and water went below to my kitchen ceiling. Insurance paid for tearing up the bathroom ceramic floor, removing toilet/sink and reset, new ceramic floor and plaster/paint to repair the kitchen ceiling. My out of pocket was the deductible and the cost of the new copper drain line.
General rule of thumb: sudden and accidental is covered; things that wear out are not.