A main shutoff valve controls water flow from the local supply into your home. When it doesn’t close properly, you might be unable to stop the flow for emergencies or repairs. However, it’s easily replaced with the right knowledge and tools. Richard Trethewey, This Old House‘s plumbing and heating expert, shows you how.
Signs of a Failing Shutoff Valve
Early detection is key to avoid water damage from a failing main shutoff valve. Look out for any of these signs you might need a replacement:
- Difficulty turning the valve on or off
- Incomplete shutoff when the valve is closed
- Leaks around the valve stem or body
- Visible corrosion or mineral buildup
Tools and Materials You’ll Need
Aside from the new valve, you’ll need these tools for a safe, efficient replacement project:
- Acetylene torch
- Bucket and towels
- Fitting brush
- Pipe wrench
- Sandpaper
- Solder and flux
- Tubing cutter
Gate Valves vs. Ball Valves
Trethewey recommends using a ball valve to replace an older gate valve. Ball valves have a stainless steel ball with a hole at their center that lets water through when the valve is open. They’re more reliable, require only a quarter turn to open and close, and have a longer lifespan since there are fewer moving parts.
Preparing To Replace the Valve
Most homes have an additional outdoor shutoff valve under the street and below the frostline. Before starting the repair process, call your local officials and have them close the valve with a special wrench. “People don’t realize that there’s one more last line of defense outside somewhere,” says Trethewey.
Once city workers have turned off the valve, Trethewey opens all faucets in the home to drain any remaining water from the pipes.
Replacing the Valve
Follow these steps to replace the valve once the water supply is off and the pipes are drained.
- Clean the main water line with sandpaper to remove corrosion and debris. “It’s always easier to do when the pipe’s in place,” comments Trethewey.
- Determine where you’ll install the new valve, and cut into the water line with a tubing cutter. You might find residual water inside the line that needs to drain out.
- Clean the inside of the new valve with a fitting brush.
- Apply flux to both the outside of the pipe and the inside of the valve for a strong solder joint.
- Use an acetylene torch to solder the new valve in place. Heat the joint until the flux bubbles, then touch the solder to the pipe opposite the flame. “The melted solder will pull right around the fitting to make a watertight seal,” says Trethewey. Allow the joint to cool.
Testing the New Valve
After installing the new valve, make sure it’s functioning correctly. Have your city turn the water back on at the street and slowly open the new valve so water can flow into your home’s pipes. Check for leaks around the valve and turn it off and on to verify everything’s functioning as expected.
