How to Replace Sink Supply Lines

Water supply lines are the unsung heroes of your vanity, quietly delivering pressure until the day they begin to bulge, corrode, or leak. While we often overlook these braided connectors, they are the single point of failure that can lead to a flooded cabinet if neglected. Upgrading to high-quality stainless steel braided lines is an inexpensive insurance policy against water damage. Done well, this project is a clean, dry, and straightforward task that anyone can handle in under an hour. The key is in the tension; you want a connection that is secure enough to hold under pressure but never so tight that you compromise the rubber gaskets or crack the plastic threading. Treat this as a routine maintenance cycle to keep your home's plumbing healthy and reliable.

1. Stop the Flow First. Locate the shut-off valves under the sink and turn them clockwise until they stop. Open the faucet handles to bleed any remaining pressure from the lines.
2. Make Your Workspace. Remove all stored items from the cabinet to give yourself room to maneuver. Place a shallow bowl or towel directly under the supply line connections to catch residual water.
3. Detach from Faucet. Use an adjustable wrench or a basin wrench to loosen the nuts connecting the supply lines to the faucet shanks. Carefully unscrew them by hand once they are loose, keeping the lines upright to minimize spills.
4. Free the Valve Connection. Loosen the nuts connecting the supply lines to the shut-off valves under the sink. Pull the lines out and place them into your collection bucket.
5. Connect the New Lines. Thread the new supply lines onto the shut-off valves first, then attach the opposite ends to the faucet shanks. Tighten by hand until you feel the gasket seat against the threads.
6. Seal It Tight. Use your wrench to tighten the nuts an additional quarter-turn past hand-tight. Do not overtighten, as this can crack the plastic or crush the gasket.
7. Verify No Leaks. Slowly open the shut-off valves and monitor the connections for moisture. If dry, turn on the faucet and let it run for two minutes while observing the joints.