Cut the supply line with a pipe cutter leaving enough room between the escutcheon plate and the cut to allow installation of the valve fitting.
Replace water shut off valve under bathroom sink.
If you have a gas water heater turn the knob to the pilot position.
Shut off the circuit breakers to an electric water heater.
If this happens to you you can simply replace the valve with a new valve that matches the old one.
When cutting the supply line cut slowly and gently so.
Then open a faucet on the lowest level of your house and another faucet on an upper level to drain the pipes.
Place a bucket under the old valve.
Turn off the next valve up the line which may be the main water supply valve.
Deburr the pipe with a deburring tool.
Open the faucet to drain the line.
Under sink shutoff valves also called fixture shutoffs or stop valves allow you to turn off the water to the sink or other fixture without having to use the home s main shutoff.
Shut off the water at the main shutoff valve.
There are two basic types straight stops and angle stops and these valves normally remain on and are seldom closed functioning maintenance free for years.