How to Fix a Leaky Plumbing Line Under a Kitchen Sink

Replacing drainpipe washers and nuts often solves leaks.

Dampness or puddles beneath a kitchen sink indicates a leak in the sink's drainpipes or in the faucet's supply lines. To determine which type of leak is responsible, carefully inspect your under-sink cabinet with a flashlight and use your hands to detect dampness around pipe fittings and valve connections. Once you locate the damaged components, repairing leaky plumbing lines is a relatively quick and simple task.

Things You'll Need

• Bucket
• Rags
• Adjustable wrenches
• Basin wrench
• Replacement water supply line
• Pliers
• Replacement drain assembly

Instructions

Water Supply Lines

1. Position a bucket and rags beneath the sink faucet's water supply valve. Twist the supply valve's handle clockwise to tighten and close the valve. Attach an adjustable wrench to the flat-sided collar of the valve. Attach an adjustable wrench to the supply line nut that meets with the supply valve.

2. Grip the wrench attached to the supply valve. Use this wrench to stabilize the valve's position while you twist the supply line's nut. Turn the wrench attached to the nut counterclockwise to loosen the nut. Keep loosening the nut until you can turn it by hand. Remove the nut by hand and allow the loose end of the supply line to drain into the bucket or onto the rags.

3. Attach an adjustable wrench or basin wrench to the remaining supply line nut. Turn the nut counterclockwise to loosen. Remove the nut by hand to release the damaged supply line from the faucet's inlet.

   Locate the side of the replacement supply line that corresponds to the sink faucet's inlet. The sink side of the line is often larger than the supply side. Press the sink side of the replacement line against the sink's inlet and twist clockwise to tighten.

4. Press the supply side of the replacement line against the supply valve's outlet. Twist clockwise to tighten. Attach an adjustable wrench or basin wrench to the sink side of the line and twist roughly one-quarter rotation beyond hand tight. Attach a wrench to the supply side and turn roughly one-quarter turn beyond hand tight. Turn on the water supply valve and check the new joints for leaks.

Drainpipe Repairs

1. Place a bucket beneath the drainpipe that you plan to remove. Locate the nuts that join the damaged drainpipe to the drain assembly. A sink's drainpipes connect to adjacent components with a slip-joint nut at each end.

2. Grasp one of the damaged pipe's nuts and rotate counterclockwise to loosen it. If you are removing a vertically-oriented pipe, such as the sink strainer tailpiece, begin at the top nut. Loosen the nut until it disengages from the pipe's threads. Slide the nut and washer away from the pipe.

3. Grasp the opposite nut and rotate counterclockwise to loosen. Loosen the nut and slide the nut and washer away from the pipe. To remove a stubborn nut, drape a rag around the nut's circumference and mount pliers over the rag.

4. Pull the loosened pipe from adjacent components. If necessary, gently bend the adjacent pipes to create more pulling room. Find a replacement pipe among the components of a replacement drain assembly. Slide the replacement pipe into place and secure the pipe to the drain assembly with washers and slip joint nuts.

Tips & Warnings

• Don't coat supply line or drainpipe threads with pipe thread sealant, as sealant compromises the connection between these types of fittings.

References

• Home Depot: Installing a New Kitchen Faucet & Side
• Keeney Manufacturing Company: P-Trap Installation