Things You'll Need
6-inch adjustable wrench
Small bucket or bowl
Plumber's Emory paper
New toilet stop valve
The small water valve that supplies water to a toilet, commonly called a "stop" valve, has only a few moving parts, but over time, mineral deposits from the water or deterioration of the internal gaskets can cause the valve to fail. In addition, many cheaper types of valves are made with plastic components that can easily crack or break from normal operation. Whatever the cause of the failure, replacing the valve is a common and economical repair. The simple procedure will restore the proper function of the supply line.
Turn the water supply off to the toilet at the home's main gate valve, typically located at the exterior of the house.
Drain the toilet tank by flushing the toilet.
Rest a small bucket or bowl under the toilet valve to catch any water left in the water line, then disconnect the water line from the toilet valve using an adjustable wrench to turn the small hex nut at the end of the line counterclockwise.
Turn the larger hex nut at the base of the toilet valve counterclockwise using an adjustable wrench to disconnect it from the valve, then pull the valve housing off of the copper water supply line.
Remove the toilet valve's large hex nut by sliding the compression ring off of the copper water line.
Remove any corrosion or mineral deposits on the copper water supply line by buffing the end with a strip of Emory paper.
Wrap the threads of both connections on the new toilet valve with two to three layers of Teflon tape wound clockwise.
Install the new toilet valve by sliding its large hex nut over the copper water supply line, keeping the open, threaded side facing outward, then slide the brass compression ring over the copper pipe. Slide the new toilet valve onto the copper line and hand-tighten the hex nut onto the end until snug.
Push the new valve completely onto the copper water line until it stops, then tighten the large hex nut one-quarter to one-half turn using an adjustable wrench.
Connect the toilet's water line to the new valve and hand-tighten the hex nut until snug, then tighten the hex nut one-quarter to one-half turn using an adjustable wrench.
Turn the main gate valve back on to restore the water supply to the toilet and check the new valve for leaks. Tighten the hex nuts, if necessary.
Open the new toilet valve and allow the toilet tank to fill.
Do not use any of the old toilet valve parts, such as the hex nuts or brass compression rings, with the new valve to prevent mismatching that might cause leakage.