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How to Repair a Damaged Main Shutoff Valve

Ask This Old House plumbing and heating expert Richard Trethewey demonstrates solutions for replacing a water main shutoff


  1. Replacing the main shutoff valve is a risky job that should be left to professionals only.
  2. If the homeowner-accessible shutoff is not holding, the water utility usually has access to another shutoff in the street.
  3. When working in a multifamily home or if the main shutoff is damaged, water can be held back temporarily by freezing the pipe. Freeze the pipe just before the main shutoff valve. Let the pipe-freezing tool work for a little while to ensure all the water in that section of pipe is frozen.
  4. Cut out the damaged main shutoff with the pipe cutter and solder on the new connection as quickly as possible. Upgrade older gate valves to a more reliable ball valve.
  5. Turn off the pipe-freezing tool and let the pipe unfreeze.


If the house’s water main shutoff malfunctions, the water utility usually has a shutoff outside the home that they can access.

Richard showed two methods of freezing a pipe when working in a multifamily home or where no outdoor shutoff is available. One uses carbon dioxide; the other is a refrigerant-based machine. Pipe freezers can be found at plumbing supply stores or rented from tool rental shops.

Richard recommends upgrading older gate valves to the more reliable ball valve, which can be found at plumbing supply stores and home centers.

Expert assistance for this segment was provided by A.E. Carter Plumbing and Heating.