Replacing a residential water main in NYC involves several key steps. Step 1: Initial inspection and assessment. Step 2: DEP permit application with engineering plans. Step 3: DOT street opening permit if needed. Step 4: Utility markouts to identify underground infrastructure. Step 5: Excavation to expose the old water main. Step 6: Disconnection and removal of the old pipe. Step 7: Installation of new copper or ductile iron pipe. Step 8: Connection to the city water main. Step 9: DEP inspection and testing. Step 10: Backfill, compaction, and street restoration. The entire process typically takes 3-7 days from start to finish.