Sink Trap Replacement: Fixing Leaks and Odors Below
The curved pipe under your sink, the P-trap, is a frequent source of trouble: it drips onto the cabinet floor, clogs with grease and debris, or lets sewer odor drift up into the room. You might notice a musty smell, a damp cabinet base, or a slow puddle that returns no matter how many times you wipe it. Because it's tucked behind cleaning supplies, a slow trap leak often goes unnoticed until the cabinet bottom swells.
A P-trap is the U-shaped section of drain pipe below the sink, and it does something deliberate: it holds a small amount of standing water that seals off the drain line so sewer gases can't rise into your home. Over time the trap can corrode, crack, clog, or loosen at its slip-joint connections, which leads to leaks or smells. Replacing it means matching the pipe size and material, usually PVC or metal, and reassembling the slip joints with their washers seated correctly. The trick is getting every joint square and snug so it seals without overtightening, which cracks plastic and creates the very leak you came to fix.
How the job is done
- 1
Clear the cabinet and place a bucket
We empty under the sink and set a pan or bucket beneath the trap, since the trap is full of water and will spill the moment it's loosened.
- 2
Loosen the slip-joint nuts
We hand-loosen the nuts at the tailpiece and the wall arm, supporting the trap so it doesn't drop, and let the standing water drain into the bucket.
- 3
Remove and inspect the old trap
We take the trap out and check the tailpiece and wall arm for corrosion, cracks, and the cause of any clog or odor, so we fix the real problem, not just the symptom.
- 4
Match the new trap
We select a trap of the correct diameter and material that lines up with the existing tailpiece and wall arm, since a mismatched trap forces the joints out of square.
- 5
Assemble with fresh washers
We fit new slip washers in the right orientation, hand-thread the nuts, and align the trap so it sits level with a proper downward slope from the sink.
- 6
Tighten and run a leak test
We snug the nuts hand-tight plus a small turn, run water through, fill the sink and release it for a heavier flow, and feel every joint for dampness.
What a pro checks
- The trap holds water on purpose; that water seal is what keeps sewer gas out, so a dry or missing trap is why a sink smells.
- Slip-joint washers must face the right direction, and reusing old hardened washers is a common reason a reassembled trap still weeps.
- We tighten slip nuts by hand plus a slight turn; cranking them with pliers cracks PVC and distorts the washer, causing leaks.
- The trap must keep a downward slope toward the wall; a trap that sags or is forced uphill drains slowly and traps debris.
- If the metal trap is corroded thin, we replace the whole assembly rather than patching one fitting that's about to fail next.
- When the leak or odor traces past the trap into the wall drain or vent, that's beyond a trap swap and may need a licensed plumber.
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Frequently asked questions
Why does my sink smell like sewage?
Usually the trap has lost its water seal, either because it dried out from disuse, leaked out, or the trap is cracked or improperly installed. That water barrier is the only thing blocking sewer gas from rising through the drain. Restoring a properly filled, sealed trap typically clears the smell.
Should my P-trap be metal or plastic?
Both work. PVC plastic resists corrosion and is common today, while older or exposed traps are sometimes chrome-plated metal for looks. We match the new trap to your existing pipe size and the connection it ties into, and either material seals well when assembled correctly.
Why does my P-trap keep leaking even after I tightened it?
Over-tightening is often the cause, since it cracks plastic nuts or deforms the washer. Other times the slip washer is old, installed backward, or the trap isn't aligned squarely. We use fresh washers, align the joints, and tighten just enough, which is what actually stops the drip.
Can I clean a clogged trap instead of replacing it?
Often yes. If the trap is sound but clogged with grease or debris, it can be removed, cleaned out, and reinstalled. We replace it when the trap is corroded, cracked, or the connections no longer seal, but a simple clog usually just needs the trap cleared.
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