How to Replace a Broken Pipe Under Your Sink

2026-2-28

How to Replace a Broken Pipe Under Your Sink

Few plumbing problems cause as much immediate panic as water gushing from a broken pipe under your sink. Whether it's a cracked P-trap, a leaking supply line, or a corroded drain pipe, a failure under your sink threatens your cabinets, flooring, and the structural integrity of your home. At Judd's Plumbing, we've helped countless homeowners navigate these repairs—and we're here to guide you through both the DIY approach and when to call in the professionals.

Assessing the Problem: What's Actually Broken?

Before you start any repair, you need to identify exactly what's leaking.

Common Under-Sink Pipe Failures:

P-Trap (Drain Pipe): The curved pipe that holds water to block sewer gases. These often crack or loosen at connections.

Water Supply Lines: Flexible braided or plastic tubes that connect shut-off valves to faucets. These burst, crack, or leak at connections.

Shut-Off Valves: The small valves where supply lines connect to wall pipes. These can fail internally or at the packing nut.

Faucet Connections: Points where supply lines attach to the faucet itself.

Trap Arm: The straight pipe extending from the P-trap into the wall.

Gathering Your Tools and Materials

Tools You'll Need:

Adjustable wrenches (two for loosening stubborn connections)
Slip-joint pliers
Bucket or large bowl (for catching water)
Towels and rags
Pipe cutter (for cutting new pipe sections)
Plumber's tape (Teflon tape)
Pipe wrench (for stubborn connections)
Flashlight (for seeing in tight spaces)

Materials (Based on Your Pipe Type):

For PVC/Plastic Pipes:

New P-trap kit (includes trap, trap arm, washers, nuts)
PVC primer and cement (for permanent connections)
Replacement washers

For Metal Pipes:

Replacement trap assembly (chrome or brass)
Replacement washers and nuts
Plumber's putty

For Supply Lines:

New flexible supply lines (measure length needed)
Replacement shut-off valve (if needed)
Plumber's tape

Step-by-Step P-Trap Replacement

Step 1: Prepare the Work Area

Clear everything from under the sink
Place a bucket directly under the trap
Lay down towels to protect cabinet floor
Have good lighting available

Step 2: Shut Off Water and Remove Standing Water

Turn off both hot and cold water supply valves
Open faucet to relieve pressure and drain remaining water
Place bucket beneath trap
Loosen slip nuts with wrench or pliers
Allow water to drain into bucket
Remove trap completely

Step 3: Inspect and Clean Connections

Check trap arm (pipe going into wall) for damage
Clean all threads and surfaces
Remove old washers and nuts
Inspect wall connection for corrosion or damage

Step 4: Assemble the New Trap

Dry-fit all pieces to ensure proper alignment
Apply plumber's tape to threads (for metal connections)
For PVC, test fit before applying cement
Start with trap arm into wall connection
Attach the J-bend (curved section)
Connect the sink tailpiece (pipe from sink strainer)
Tighten all slip nuts hand-tight, then 1/4 turn with wrench

Step 5: Test for Leaks

Place bucket under connections
Slowly turn water supply back on
Run water and watch for drips
Tighten connections slightly if needed (don't overtighten)

Replacing Water Supply Lines

Step 1: Shut Off and Drain

Turn off angle stop valves (hot and cold)
Open faucet to release pressure
Place towels beneath connections

Step 2: Remove Old Supply Lines

Use wrench to loosen nut at shut-off valve
Use second wrench to loosen nut at faucet
Remove old line completely

Step 3: Install New Supply Lines

Check that new line is correct length (not stretched tight or excessively coiled)
Apply plumber's tape to valve threads if needed
Hand-tighten connections, then 1/4 turn with wrench
Ensure lines are not kinked or twisted

Step 4: Test

Slowly open shut-off valves
Check for leaks at both connection points
Run faucet to test flow

Replacing a Shut-Off Valve

This repair requires more skill and carries higher risk. Call Judd's Plumbing if you're unsure about any step.

If You Proceed:

Shut off main water supply to the house
Open faucets to drain remaining water
Use two wrenches (one to hold pipe, one to remove valve)
Clean pipe threads thoroughly
Apply plumber's tape (3-4 wraps clockwise)
Install new valve hand-tight, then snug with wrench
Turn main water back on slowly and check for leaks

PVC vs. Metal Pipes: What You Need to Know

PVC/Plastic Pipes

Advantages:

Easier to cut and assemble
Resistant to corrosion
Less expensive

Installation Notes:

Use PVC primer before cement for proper bond
Cement sets quickly—have all pieces positioned before applying
Allow proper curing time before testing

Metal Pipes (Chrome, Brass)

Advantages:

Traditional appearance
Durable when properly maintained

Installation Notes:

Use two wrenches to prevent twisting
Plumber's tape essential for threaded connections
Avoid overtightening (can crack fittings)

When to Call Judd's Plumbing

While many under-sink pipe repairs are DIY-friendly, certain situations demand professional expertise:

1. You Can't Access the Problem

If the leak is behind walls, inside cabinets with no clearance, or requires removing cabinets or countertops, call a professional.

2. Pipes Are Corroded or Stuck

If connections won't budge with reasonable force, forcing them can cause pipe failure behind walls.

3. The Wall Connection Is Damaged

If the pipe coming from the wall is corroded, broken, or the connection is failing, this requires wall opening and professional repair.

4. You've Attempted Repair and Still Leaks

Sometimes what seems like a simple P-trap leak is actually a failing pipe behind the wall. A professional can properly diagnose.

5. Multiple Leaks or System-Wide Issues

If you're experiencing multiple pipe failures, this may indicate systemic problems (corrosion, pressure issues, aging pipes) requiring comprehensive assessment.

6. You're Uncomfortable with Any Step

Never proceed with a repair if you're uncertain. A small mistake can cause extensive water damage.

Preventing Future Under-Sink Pipe Failures

Regular Inspections

Check under sinks monthly for drips or moisture
Feel around connections for wetness
Look for early signs of corrosion or discoloration

Proper Usage

Avoid storing heavy items that could bump pipes
Don't hang items from pipes
Avoid pouring harsh chemicals down drains

Maintenance

Tighten loose connections promptly
Replace old supply lines every 5-10 years
Consider upgrading aging shut-off valves

Temperature Protection

Keep cabinet doors open during extreme cold (even in Arizona)
Insulate pipes in exterior walls

Protect Your Home with Proper Repairs

A broken pipe under your sink is more than an inconvenience—it's a threat to your home's structure and your peace of mind. Whether you tackle it yourself or call for professional help, addressing the problem quickly and correctly prevents costly water damage.

Need Professional Help with Under-Sink Plumbing?
Call Judd's Plumbing at 623-304-5833
Visit: juddsplumbingaz.com

Your home deserves the right approach to every repair. Whether you're tackling it yourself or calling for backup, Judd's Plumbing provides the expertise and support you need.