How to Replace a Leaky Angle Stop (Shutoff Valve) Under Your Sink

Gather all necessary tools and materials before starting the project to ensure a smooth workflow. Place a bucket and several rags or paper towels under the sink where you will be working to catch any water that will spill out. Ensure your new angle stop matches the pipe type and size (e.g., 1/2-inch nominal compression for the wall pipe) and the faucet supply line size (typically 3/8-inch OD compression).

Locate the main water shutoff valve for your home. This is often in a basement, crawl space, utility closet, or outside near the water meter. Turn the valve handle clockwise until it is fully closed. To confirm the water is off, turn on any faucet in the house (preferably the one you are working on). The water flow should slow to a trickle and then stop completely.

After shutting off the main water supply, relieve the pressure in the lines. Open the hot and cold handles on the faucet connected to the leaky valve. This will allow any remaining water in the supply lines to drain out into the sink. Place your bucket underneath the angle stop to prepare for the next steps.

Using an adjustable wrench, turn the nut that connects the faucet supply line to the top of the angle stop counter-clockwise. A small amount of water will drain from this line into the bucket below. Once the nut is loose, fully disconnect the supply line and move it out of the way.

This step requires two wrenches. Use one adjustable wrench (or channel-lock pliers) as a 'backup' to hold the copper pipe coming from the wall securely, preventing it from moving. Use the second adjustable wrench to grip the large compression nut on the back of the angle stop and turn it counter-clockwise. Once the nut is loose, you should be able to slide the entire old angle stop, including the nut and the old compression ring (ferrule), off the end of the pipe.

Once the old valve is off, thoroughly inspect the end of the copper pipe. Use a rag to wipe away any old plumber's putty, dope, or debris. Take a piece of emery cloth and gently sand the last inch of the pipe where the new compression ring and nut will sit. The goal is to create a clean, smooth, and slightly scuffed surface for the new components to seal against.

Take the new angle stop and disassemble it. First, slide the new compression nut onto the copper pipe, making sure the threads face towards the end of the pipe. Next, slide the new compression ring (ferrule) on, with its tapered end pointing towards where the valve will be. Push the body of the new angle stop firmly onto the pipe until it stops. Slide the nut and ferrule up to the valve body and hand-tighten the nut. Now, use the two-wrench technique again: one wrench to hold the valve body steady (pointing in its final desired orientation) and the second wrench to tighten the compression nut. Tighten the nut about one-half to three-quarters of a turn past hand-tight. Do not over-tighten.

With the new angle stop installed, re-attach the flexible faucet supply line to the valve's outlet. Hand-tighten the nut to ensure it is not cross-threaded. Then, use an adjustable wrench to give it a final gentle tightening, usually about a 1/4 turn. These connections don't require extreme force.

First, ensure the new angle stop is in the 'off' position (handle should be perpendicular to the pipe). Go to your main water shutoff and turn it on SLOWLY. Listen for any sounds of rushing water. Return to the sink and meticulously inspect the new valve. Wipe all connections with a dry paper towel and watch for any beads of water forming, which would indicate a leak. If it's dry, place a dry towel under the valve and slowly turn the angle stop handle to the 'on' position. Let the water run at the faucet for a minute to bleed out air. Perform a final, thorough inspection of all connections for any drips or moisture.