Replacing a damaged toilet inlet valve on your own makes sense environmentally as well as economically. A leaky toilet can waste up to 80,000 gallons of water a year, and there is no point in paying a professional to do a relatively simple job that you can do yourself.
Turn off the water supply shutoff valve, which is located to the left of the toilet and close to the floor. Remove the cover of the tank. Flush the toilet to empty all water from the tank into the bowl. Use a sponge or towel to remove the remaining water from the tank so that nothing leaks onto the floor once you remove the toilet inlet valve.
Use the adjustable wrench to disconnect the water-supply line from the bottom of the outside of the tank, where it enters the fill valve.
Use the adjustable wrench to remove the retaining nut that holds the inlet valve to the bottom of the outside of the tank. The inlet valve, also called the fill valve or the tank valve, is the tall column standing off-centre in the tank, with a float attached to it.
Remove the small plastic tube that runs from the top of the toilet inlet valve to the overflow tube, which is the column standing in the centre of the tank.
Lift the toilet inlet valve out of the tank. Wash the ceramic where it was attached to ensure a tight seal with the replacement valve.
Place the new washer from the new inlet valve over the inlet-valve hole in the tank. Insert the new valve on top of the washer. Tighten the retaining nut on the outside of the tank. Tighten the nut with your fingers, and then give it another half-turn with the adjustable wrench. Over-tightening the nut can crack the toilet tank.
Reattach the inlet hose with your fingers, and then give it a half-turn with the adjustable wrench. Reattach the small tube that runs from the new toilet inlet valve to the overflow valve. Turn the water supply on, and check for leaks in the tank and around the inlet hose.
Check the fill level of the tank. It should be about 3/4 inch from the top of the overflow valve. If it is not, you need to adjust the float up or down until you have reached the desired point. Either use the float-adjustment screw on top of the inlet valve, if your inlet valve has one, or bend the float arm if it does not.