Most main breaks occur in the most prevalent diameters of pipe, 6 and 8. The MWW repairs an average of 575 main breaks per year (Average 2007-2017). Because water mains are under great pressure, even a small hole can allow large amounts of water to escape. The average cost of repairing a broken water main is $2,400.00. The water main repair response When a main break or water leak in the street is reported, our Control Center dispatches a Field Investigator to assess the situation and determine the appropriate utility response, authorize the call-out of repair crews if needed, and assist in obtaining materials, supplies, maps, and records to expedite repairs.