How to Replace a Toilet Water Supply Line

Begin by preparing your work area. Place old towels or a shallow bucket on the floor beneath the toilet's water supply line and shutoff valve to catch any residual water. Locate the shutoff valve, typically an oval-shaped handle on the wall or floor behind the toilet. Turn the handle clockwise until it stops. Do not force it. To empty the toilet tank, flush the toilet and hold the handle down until as much water as possible has drained from the tank. A small amount of water will remain in the tank, which is normal.

With the bucket in position, start by disconnecting the supply line from the shutoff valve. Use an adjustable wrench or channel-lock pliers to grip the coupling nut on the supply line and turn it counter-clockwise. You may need a second wrench to hold the valve body itself to prevent it from turning. Once loosened, you should be able to unscrew it by hand. Next, locate the plastic coupling nut connecting the supply line to the underside of the toilet tank's fill valve. This nut is usually plastic and can often be loosened by hand. If it is too tight, use channel-lock pliers gently to start it, then unscrew it the rest of the way by hand. Be prepared for a small amount of water to drain from the line.

Take your new Toilet Water Supply Line. First, attach the top coupling nut (typically plastic) to the threaded shank of the toilet fill valve extending from the bottom of the tank. Thread it on by hand, turning clockwise until it is snug. Ensure it is not cross-threaded. Once hand-tight, use a wrench or pliers to give it an additional quarter-turn. Do not overtighten. Next, align the bottom coupling nut (typically metal) with the threaded outlet on the shutoff valve. Thread this nut on by hand until it is snug. Then, using an adjustable wrench, tighten it another quarter to half-turn until it feels secure.

Before turning the water on, double-check that both connections are snug. Slowly turn the shutoff valve handle counter-clockwise all the way to open the line. You will hear water flowing into the toilet tank. As the tank fills, carefully inspect both the upper and lower connection points for any signs of water. Look and feel for drips. To be certain, wipe both coupling nuts and the surrounding area with a dry paper towel. Check the paper towel for any moisture. If you detect a leak, turn the water off and tighten the leaking connection slightly (about an eighth of a turn), then test again. Once the tank is full and the fill valve stops, flush the toilet once to ensure everything operates correctly under pressure, and check for leaks one last time.