Elementary school about three years old. Spent the major portion of the day removing concrete and mud to get close enough to see what was causing the leak. Finally discovered that the 4" main line had pushed out of a tee causing the leak. Tee supplies a valve that operates some tree well bubblers. Probably had been leaking from the get-go and finally got big enough to push its way out of the sidewalk. Repairs and backfilling with wetted sand are on the agenda for tomorrow.