Replace a Dishwasher Supply Line

Water doesn't announce its intentions. The dishwasher supply line running from your shut-off valve to the machine inlet works quietly for years until it doesn't—and by then you're looking at a puddle spreading across the kitchen floor. Most supply lines fail not from dramatic ruptures but from slow seepage at compression fittings or pinhole leaks where the line bends behind the machine. The rubber-and-plastic lines installed by builders rarely last more than a decade. Braided stainless steel lines outlive them by twenty years and cost twelve dollars. Replacing the line before it fails means you choose the timing. The job requires no special skills, just methodical hands and fifteen minutes of access to the space under your sink. You'll disconnect the old line at both ends, measure for the correct replacement length, and install new fittings that seal properly on the first attempt. When you're done, you'll have the mechanical confidence that comes from fixing something before the emergency dictates the schedule.

1. Kill the Water First. Locate the dishwasher shut-off valve under the kitchen sink—it's a small angle valve on the hot water line, usually brass or chrome with a red or blue handle. Turn it clockwise until it stops. Then go to your electrical panel and flip the breaker labeled for the dishwasher, or unplug the unit if it uses a plug connection under the sink.
2. Disconnect from Valve. Place a shallow pan or folded towel under the valve to catch residual water. Use an adjustable wrench to turn the compression nut at the shut-off valve counterclockwise. The nut connects the supply line to the valve outlet. Once loose, unthread it by hand and pull the line free. Water will drip from the line—this is normal.
3. Expose the Inlet. Open the dishwasher door and remove the lower dish rack. Unscrew the kickplate at the bottom front of the machine—usually four screws along the top edge. With the kickplate removed, you'll see the inlet valve on the left side where the supply line connects. Use a flashlight to locate the brass compression fitting.
4. Free the Old Line. Place a towel under the inlet valve. Use your adjustable wrench to loosen the compression nut connecting the supply line to the inlet—turn counterclockwise. Once loose enough to turn by hand, unthread it completely and pull the old supply line out from behind the dishwasher. Note how the line was routed so you can follow the same path with the replacement.
5. Attach at Valve. Measure the old line or estimate the distance from the shut-off valve under the sink to the dishwasher inlet—most installations need a 60-inch line. Thread the compression nut onto the new braided stainless steel line first, then insert the ferrule. Push the line onto the shut-off valve outlet and hand-tighten the nut clockwise. Use your wrench to give it one additional quarter-turn past hand-tight—no more or you'll damage the ferrule.
6. Connect to Dishwasher. Feed the new supply line through the cabinet opening and behind the dishwasher, following the same path as the old line. Avoid sharp bends that kink the line. At the inlet valve, thread the compression nut onto the inlet fitting by hand, then use your wrench for one quarter-turn past hand-tight. Make sure the line has a gentle curve with no tension pulling on either connection.
7. Check for Leaks. Turn the shut-off valve counterclockwise to restore water flow. Watch both connections closely for sixty seconds—any seepage will show immediately as beads of water at the compression nuts. If you see leaks, turn off the valve and tighten the leaking nut another eighth-turn. Once both connections are dry, flip the dishwasher breaker back on.
8. Verify Operation. Replace the dishwasher kickplate and secure it with the original screws. Check under the sink one final time for moisture around the shut-off valve connection. Run a full cycle and inspect the area under the dishwasher and sink during the fill phase to confirm everything stays dry.