If your old toilet keeps on running after the tank has refilled with water after flushing, you may need to replace the old fill valve to stop wasting water. A broken fill valve won't shut the water off and it'll allow the water to keep on flowing into the tank and down the drain in the toilet – increasing your home water costs and waste. To fix the problem, you need to replace the fill valve. Here is how you can replace the fill valve on a standard toilet.
You need to turn the water off and remove all of it from the tank to avoid flooding your bathroom floor while you are working on the toilet. Turn the handle on the water supply line clockwise until it stops to turn off the water.
Flush the handle on the toilet a couple of times to drain as much water out of the tank as you can. You'll need to use a large sponge or rag to soak up the water in the bottom of the tank. Once the water is removed, you can take the nut off from the bottom of the toilet tank that holds the fill valve in place.
Remove Fill Valve
Remove the water line going into the fill valve with channel locks. Set the water line aside. Remove the nut to the bottom of the fill valve mechanism. Disconnect the float and the overfill tube from the fill valve. Lift the old valve out of the toilet tank.
Replacing the Fill Valve
You need to make sure you obtain a fill valve that is specifically made for your toilet. Fill valves, like toilet handles and other parts, can have subtle differences in their design that will prevent the fill valve from as performing as expected in your toilet. Make sure to mark the manufacturer and model of the toilet on a piece of paper before you go the plumbing or hardware store.
Slide the end of the new fill valve through the hold in the bottom of the tank. Put the nut back on that secures the fill valve to the bottom of the tank. The new nuts are usually made of out of plastic, so be extra careful not to overtighten it, as doing so can strip the threads on the fill valve.
Replace the float and the overfill tube. You will usually have to readjust the float so it shuts off the water before it reaches the overflow pipe. Place the overflow tube into the overflow pipe. Restore the water line to the fill valve. Allow the tank to fill up with water. Flush the handle a couple of times to make sure everything works correctly.
If you have any issues, consider calling a Plumbing Now plumber.