The short answer
Check the Leak Source First
Look under the sink with a flashlight. Dry the pipes with a rag, then run water and watch where the drip starts. A leak at the top or bottom of the curved trap usually comes from a loose slip nut or a worn washer. A crack in the trap itself shows as a steady drip along the bend.
If the leak is at a joint, tighten the nut with a wrench by hand, turning clockwise. Do not overtighten, as that can crack the fitting. If the drip continues, the washer inside may be flattened or damaged. Take the nut off, inspect the washer, and replace it if it looks worn.
Tools and Materials You Need
A basic repair needs a channel-lock or adjustable wrench, a bucket, and a rag. Most hardware stores sell replacement P-trap kits that include the curved pipe, nuts, and washers. You may need a hacksaw if the old trap is glued or corroded. Wear gloves to protect your hands from sharp edges.
Before you start, place a bucket under the trap to catch water left in the pipe. Loosen the nuts carefully, as water will spill out. If the trap is plastic, use gentle pressure. Metal traps may need penetrating oil to loosen stuck threads. Work slowly to avoid damaging the drain pipes above or below.
- Adjustable wrench or pliers
- Replacement washers and nuts
- New P-trap kit if cracked
- Bucket and old towels
- Pipe wrench for stubborn fittings
- Safety glasses for debris
Step-By-Step Replacement
Turn off the water supply to the sink and open the faucet to drain the lines. Place the bucket under the trap. Loosen the two slip nuts that connect the trap to the tailpiece and the wall pipe. Slide the nuts and washers off, then pull the trap down. Clean the ends of the pipes with a rag.
Install the new trap by sliding the nuts and washers onto the pipe ends, then attach the trap. Hand-tighten the nuts, then give each a quarter turn with the wrench. Run water and check for drips. If a leak persists, adjust the nuts slightly. Avoid using plumber's tape unless the threads are damaged.
When to Call a Plumber
You can handle a simple leak, but some situations need a professional. If the drain pipes are galvanized steel or lead, or if the leak is behind the wall, stop and call a plumber. Corroded or rusted pipes may break during removal, causing a larger mess. A plumber has the cutting tools and experience to replace sections safely.
Also, if the trap is not the source and water pools around the floor or under the cabinet, the leak may come from the sink drain flange or the supply lines. Those repairs often require disconnecting the sink. A plumber can diagnose the exact issue and fix it without causing damage to the countertop or cabinetry.
Clean Up Water Damage
After fixing the leak, dry all wet surfaces under the sink. Wipe down the cabinet floor and walls with a clean rag. If water soaked into wood, use a fan to circulate air and speed up drying. Leaving moisture can lead to swelling, warping, and mold growth over time.
For significant water that spread beyond the cabinet, you may need water damage help. Local water damage pros can inspect for hidden moisture in the subfloor or drywall. They use moisture meters to find wet spots and set up drying equipment. If you live in Quincy, keep your shutoff valve location written down for future emergencies.
- Dry all surfaces with towels
- Run a fan for 24 hours
- Check for soft wood or stains
- Watch for musty odors
- Call pros for hidden moisture
Talk to someone now
Call (617) 404-2753 any time, day or night, and describe what happened.
Call Now (617) 404-2753Frequently asked questions
How do I know if the leak is from the P-trap or the sink drain?
Run water and watch where the drip starts. If it comes from the curved pipe or the nuts on either end, it is the trap. If it drips from the top flange where the drain meets the sink, the leak is the drain seal. Dry the pipes first to see the exact source.
Can I use tape or sealant to stop a P-trap leak?
Temporary tape or putty may slow a drip, but it will not hold long under water pressure. A cracked trap needs replacement. For a loose nut, tightening or replacing the washer solves it. Sealants often fail and make a mess, so a proper repair is more reliable.
What if the P-trap is glued to the pipe?
If the trap is glued with PVC cement, you cannot unscrew it. You will need to cut the pipe with a hacksaw or pipe cutter. Measure carefully and use a coupling to connect the new trap. If you are unsure, a plumber can cut and replace it without risking damage.