How to Install a Water Shut-Off Valve
Replace an old or leaking under-sink water shut-off valve with a reliable quarter-turn compression angle stop to protect your home from water damage.
- Read the tools, materials, safety notes, and steps below for free.
- Tap Start Camera Coach when you want hands-free voice help.
- Allow camera and microphone. Point your phone at the work; the coach watches your progress and tells you the next step.
🧰 Required Tools & Equipment
- ✓ Adjustable wrench (2 required)
- ✓ Mini tubing cutter
- ✓ Small utility bucket
- ✓ Emery cloth or fine wire brush
- ✓ Deburring tool
📦 Materials & Supplies
- ✓ 1/2-inch nominal x 3/8-inch OD compression angle stop valve
- ✓ Brass compression ferrule (sleeve)
- ✓ Compression nut
- ✓ Clean absorbent rags
⚠️ Safety Checkpoints & Warnings
- • Verify the home's main water shut-off is 100% closed before turning any nuts under the sink.
- • Open the lowest faucet in the house to bleed line pressure before cutting or loosening fittings.
- • Keep electrical cords and outlets clear of dripping water beneath the sink basin.
📋 Step-by-Step Guide (6 Steps)
Shut Off Water Supply and Relieve Pressure
Turn the main water shut-off valve completely clockwise or perpendicular to the pipe. Open the target faucet and the lowest faucet in your home to drain residual water and depressurize the plumbing line. Place a catch bucket directly underneath the old shut-off valve.
- • Target faucet stops dripping completely when opened.
- • Catch bucket positioned directly underneath the pipe stub-out.
- • Failing to open a lower faucet, leaving pressurized water trapped in the pipe.
Disconnect Old Valve and Supply Line
Use one wrench to hold the valve body still and a second wrench to loosen the upper supply line nut. Once disconnected, grip the valve body with one wrench and turn the rear compression nut counterclockwise to detach the old valve. Slide the old valve off the copper stub-out.
- • Braided supply line hanging freely with threads fully exposed.
- • Old valve body removed from the copper pipe stub.
- • Twisting only the nut without backing up the valve body, bending the copper pipe inside the wall.
Clean and Prep the Copper Stub-Out
Examine the exposed copper pipe for deep scratches, ovaling, or old ferrule damage. If the old ferrule is stuck or the pipe is deformed, cut off the last 1/2 inch squarely using a mini tubing cutter. Polish the outer pipe surface with emery cloth until the copper is bright and smooth, then ream the inside rim.
- • Clean, shiny copper pipe end with a perfectly square cut and no green corrosion.
- • Inner and outer edges smooth with no sharp burrs.
- • Tightening the tubing cutter wheel too fast, crushing the pipe out-of-round.
Install Compression Nut and Ferrule
Slide the new compression nut onto the copper pipe with its internal threads facing the cut pipe end. Slide the brass compression ferrule (brass ring) onto the pipe immediately after the nut. Ensure the pipe extends past the ferrule cleanly without cocking the ring sideways.
- • Nut resting on pipe behind ferrule with open threads facing forward.
- • Brass ferrule sitting straight and level on the copper tube.
- • Installing the compression nut backwards with threads facing the wall.
- • Using pipe thread tape (Teflon) or pipe dope on compression threads.
Seat and Tighten the Valve Body
Push the new angle stop valve firmly onto the copper pipe until it bottom outs completely against the internal stop shoulder. Slide the ferrule and nut up to the valve threads and hand-tighten until snug. Hold the valve body in position with one wrench and tighten the compression nut with the second wrench 3/4 to 1 full turn past hand-tight.
- • Valve outlet pointing directly toward the fixture supply intake.
- • Compression nut fully seated with only 1 to 2 threads visible behind it.
- • Over-tightening the nut, which distorts the brass ferrule and causes permanent leaks.
Reconnect Supply Line and Pressure Test
Thread the braided faucet supply line onto the top outlet of the new shut-off valve, tightening by hand plus 1/4 turn with an adjustable wrench. Ensure the new valve handle is in the OFF position (perpendicular to body). Turn on the main home water supply slowly, inspect the valve joints with a dry paper towel, then turn the new valve handle to ON to check the final fixture.
- • New valve handle turned parallel to flow with zero water droplets forming at joints.
- • Dry paper towel wiped around all connections comes away completely dry.
- • Opening the main water valve at full velocity, creating a hydraulic water hammer.
Credit: inspired by an original tutorial by seejanedrill — watch the original on YouTube.
Don’t have everything?
- No Mini tubing cutter? Fine-tooth hacksaw blade (32 TPI) with masking tape wrap as a cut guide
- No Emery cloth? 220-grit wet/dry sandpaper or 0000 steel wool