[header] How to replace a toilet fill valve [title] Turn off the water supply. [step] Before doing any repairs to your toilet you should turn off the water outside of the toilet. You should have a water valve directly below the toilet tank. 
It should be located between where the water pipe comes out of the wall and where it attaches to the bottom of the toilet tank. [substeps] In most cases, you will turn the water shutoff valve clockwise to turn it off.