Replace a Water Supply Line

Water supply lines fail without warning. The flexible tube connecting your shutoff valve to a faucet or toilet starts as a quiet drip, then becomes a spreading puddle, then becomes an emergency at three in the morning. These lines wear out from constant pressure, mineral deposits, and metal fatigue. Replacing one before it fails is preventive maintenance. Replacing one after it fails is damage control. Either way, the work takes twenty minutes and requires no special skills. The old supply lines were chromed copper or vinyl-wrapped plastic. They kinked, corroded, and cracked. Modern braided stainless steel lines are flexible, durable, and rated for decades of service. Switching to them is cheap insurance. The connection points are simple: one end threads onto the shutoff valve under the sink or toilet, the other onto the fixture tailpiece. No soldering, no pipe dope, no glue. Just hand-tighten, then a quarter-turn with a wrench. Done properly, you'll never think about that supply line again.

1. Kill the Water Flow First. Turn the shutoff valve clockwise until it stops. It's the small oval or round handle on the water line coming out of the wall or floor. Open the faucet or flush the toilet to release pressure and drain any remaining water. Place a bucket or towel under the connection point to catch residual drips.
2. Loosen and Detach Top. Use an adjustable wrench or basin wrench to loosen the coupling nut where the supply line connects to the faucet tailpiece or toilet fill valve. Turn counterclockwise. If it's stuck, apply gentle pressure and work it back and forth. Once loose, unscrew by hand and pull the line free.
3. Disconnect the Base. Loosen the coupling nut at the bottom end of the supply line where it connects to the shutoff valve. Turn counterclockwise with your wrench. Once loose, unscrew by hand and remove the old line completely. Inspect both connection points for debris or old rubber gasket fragments and wipe clean with a rag.
4. Choose Your New Line. Measure the distance from the shutoff valve to the fixture connection point, adding a few inches for the curved path the line will take. Braided stainless steel supply lines come in standard lengths from 12 to 60 inches. Choose the size that allows a gentle curve without kinking or stretching tight. Check that both ends have the correct fitting size for your connections, typically 3/8-inch compression on both ends for faucets, or 3/8-inch compression to 7/8-inch ballcock for toilets.
5. Attach the Base First. Thread the coupling nut at one end of the new supply line onto the shutoff valve outlet by hand. Turn clockwise until it's finger-tight and the rubber gasket inside seats against the valve. Then use your wrench to tighten an additional quarter-turn. Don't overtighten—you'll crush the gasket and cause a leak.
6. Secure the Top Connection. Route the free end of the supply line up to the faucet tailpiece or toilet fill valve, allowing a natural curve. Thread the coupling nut onto the connection point by hand, turning clockwise. Tighten finger-tight first, then add a quarter-turn with your wrench. Again, snug is enough—overtightening damages the gasket.
7. Spot Leaks Immediately. Slowly turn the shutoff valve counterclockwise to restore water flow. Watch both connection points closely for drips or seepage. Let the water run for thirty seconds. If you see moisture, turn off the valve and tighten the leaking connection another eighth-turn. Repeat until dry.
8. Confirm Under Pressure. Wipe down the area and remove your bucket and tools. Run the faucet at full pressure or flush the toilet twice to confirm the line holds under working conditions. Check the connections one more time after ten minutes of use. If everything stays dry, the job is complete.