Pipe under sink leaking at connection

Quick answer

Turn off the water supply, dry the area, and inspect the connection for loose fittings or worn washers. Tighten with a wrench if possible, or replace the washer or coupling to stop the leak.

Confirm the symptom

• Water pooling under the sink near a pipe joint
• Dripping from a visible pipe connection
• Dampness or corrosion around a coupling or fitting
• Leak appears after tightening the faucet or aerator

Tools and prep

• Adjustable wrench or pipe wrench
• Plumber's tape (Teflon tape)
• Replacement washers or coupling (if needed)
• Bucket or towel to catch water
• Turn off water supply before starting
• Protective gloves and safety glasses

Step-by-step troubleshooting

1. Shut off water supply
   Do: Locate and turn off the shut-off valves under the sink. If none exist, turn off the main water supply.
   Observe: Water stops flowing from the faucet.
   Means: Water is safely off for repairs.
   Next: Dry the area and inspect the leak.
2. Dry and inspect the area
   Do: Use a towel or let the area air dry to clearly see the leak location.
   Observe: Identify the exact connection point (e.g., P-trap, supply line, or faucet connection).
   Means: You can target the correct part for repair.
   Next: Check for loose fittings.
3. Check for loose fittings
   Do: Use an adjustable wrench to gently tighten the connection. Avoid over-tightening.
   Observe: Leak reduces or stops.
   Means: The connection was loose and needed tightening.
   Next: If the leak persists, inspect the washer or coupling.
4. Inspect washer or coupling
   Do: Look for worn, cracked, or missing washers or damaged couplings. Remove the connection if necessary to examine parts.
   Observe: Damaged or missing sealing components.
   Means: The washer or coupling is compromised and needs replacement.
   Next: Replace the faulty part.
5. Replace faulty part
   Do: Install a new washer or coupling, applying plumber's tape to threads if needed. Reassemble the connection.
   Observe: Leak stops and connection is secure.
   Means: The repair is successful.
   Next: Test the connection by turning water back on slowly.
6. Test the repair
   Do: Turn the water supply back on and check for leaks at the connection.
   Observe: No water leaks from the repaired connection.
   Means: The repair is complete and effective.
   Next: Monitor for recurring issues.
7. Monitor for recurring issues
   Do: Check the connection periodically over the next few days for any signs of new leaks.
   Observe: No new leaks or dampness.
   Means: The repair is stable and long-term.
   Next: Finalize the repair.

Common causes

Parts matching

Choose the right part based on the connection type and damage observed.

• Measure the pipe diameter and thread size to ensure compatibility.
• Select a coupling or washer that matches the material (e.g., brass, plastic).
• Use a threaded coupling for metal pipes and a slip coupling for plastic.
• Check for a manufacturer's part number on the existing component if possible.
• Purchase a P-trap kit if the issue involves the drain connection.

Take the old part to the hardware store for an exact match if unsure about measurements.

When to call a professional

• The leak continues after replacing all visible parts and tightening connections.
• You notice significant corrosion or damage to the pipe itself.
• You're unable to shut off the water supply effectively.
• The connection involves gas lines or electrical components.
• The repair requires cutting or soldering pipes beyond basic skills.

FAQ

Related guides

• under sink plumbing leak

Related searches: sink pipe leak repair, under sink water leak, leaking pipe connection fix, sink P-trap leak, faucet supply line leak, drain pipe under sink leaking, sink pipe coupling replacement, leaky water supply line under sink, sink pipe washer replacement, sink pipe tightening tool