Crescent wrench or channel lok pliers
Replacement fill valve (available at home, hardware and plumbing stores for about $10)
How to Check a Fill Valve
1. Remove the lid from the toilet tank
2. When you flush a toilet, water is released from the tank and the float falls to the bottom of the tank, it opens a valve allowing water to run back into the tank. When water level is over the top of the tube, your toilet will run continuously.
3. Adjust water level by either adjusting the float arm or if your existing valve has an adjusting screw, turn the screw so the valve will shut off at a lower level.
4. Even after changing the water, if water keeps on running after the float rises. Then you have to replace your fill valve.
How to Replace a Fill Valve
1. Turn off the water and flush the toilet.
2. Take off the toilet tank lid.
3. Use a large sponge to remove any water left in the bottom of the toilet tank.
4. Use a crescent wrench or pair of channel lock pliers to undo the nut on the bottom of the tank that’s holding the fill valve and the valve should lift out, then remove the rubber tube running from the valve to the overflow tube.
5. While you have the valve out, clean around the hole in the tank to make sure there aren’t any small particles in the tank that could cause leaks at the base.
6. Your new fill valve should come in a kit that includes new washers for the base of the valve. Place one washer on the bottom of the valve and place it in the hole in the bottom of the tank.
7. Put another washer on the bottom of the valve on the outside of the tank and replace the nut holding it in place. Be careful not to tighten too much or you could crack your toilet tank. Inside the tank, attach the overflow tube to the valve.
8. Turn the water back on, flush the toilet and check for leaks to make sure the new valve is working properly. If necessary, adjust the water level to the proper depth.
9. Finish up by replacing the toilet tank lid.
When in doubt call a plumber!