Smell after plumbing repair

Under-sink plumbing after repair where odor began

Quick Answer:

If a new smell appears at a sink after recent plumbing work, first check for an open fitting or a dry P-trap. Small mistakes during a repair — a loose drain connection, an empty trap, or an overlooked fitting — are the most common causes and are usually fixable without major work.

Why This Happens

  • When a trap (the curved pipe below the sink) is empty or disturbed, sewer gases can come up the drain.
  • A fitting left open or a disconnected hose under the sink lets odors escape into the cabinet and the room.
  • Work on related parts (dishwasher, garbage disposal, or vent) can affect seals or allow air paths that produce smell.
  • Occasionally the odor is coming from the overflow or residual water in the sink rather than a plumbing connection — see Odor from overflow hole for details to check.

Step-by-Step What to Do

1. Smell to confirm and locate

  • Stand near the sink and try to pinpoint if the smell is strongest at the drain, under the cabinet, or at a nearby appliance.
  • Open cabinet doors and sniff around plumbing joints to localize the source.

2. Look under the sink for open fittings

  • Look under the sink for any open fittings left after the repair. Don’t forget to check supply lines, drain connections, and hose clamps.
  • Feel for moisture or drips — a small leak often accompanies a loose or poorly seated connection.

3. Check the P-trap and run water

  • Run hot and cold water for a minute to refill the trap and flush any lingering gases or debris.
  • If the trap is removable and you are comfortable doing so, put a bucket underneath, remove and inspect it for blockages or loose joints, then reinstall securely.

4. Inspect the garbage disposal and dishwasher connections

  • Make sure the disposal is seated properly and the dishwasher drain hose is connected and clamped.
  • Run the disposal with water to clear trapped food and check whether the smell lessens.

5. Check the overflow and sink surface

  • Clean the overflow slot and sink rim; trapped residue can smell. If the odor seems to come from the overflow, review information on Sink smells only at night and related checks for timing and patterns.
  • Use a small brush and a mixture of warm water and mild detergent to wipe away buildup.

6. Final verification

  • After tightening or reseating any fittings, run water again and recheck for smell and leaks.
  • If you found and fixed an open fitting, monitor the area for the next day to ensure the smell does not return.

What Not to Do

  • Do not overtighten new fittings trying to stop an odor. Overtightening can crack plastic parts or strip threads, causing bigger leaks.
  • Do not mix chemical cleaners in the drain — some combinations are dangerous and can damage pipes.
  • Avoid lighting candles or using strong fragrances to mask a smell before locating the source; that hides the problem instead of fixing it.

When to Call a Professional

  • Persistent sewer-like smell after you’ve checked fittings, traps, and appliances.
  • Visible leaks you can’t isolate or repair safely, or signs of water damage in cabinets or floors.
  • If you suspect a venting problem, sewer line issue, or the smell is coming from multiple fixtures.
  • If you’re not comfortable disassembling the trap or working under the sink, call a plumber to avoid accidental damage.

Safety Notes

  • Turn off water supply valves before disconnecting supply lines or drains to avoid flooding.
  • If using gloves or tools, use ones appropriate for plumbing work; protect the cabinet area with a towel or container to catch drips.
  • Avoid mixing chemical drain cleaners with other substances; if a chemical has been used recently, ventilate the area and follow label safety instructions.
  • If you smell a strong rotten-egg odor (natural gas), leave the house and contact your gas company — this is not a drain issue and requires immediate attention.

Common Homeowner Questions

  • Why did the smell start right after the repair?
    A small loose or open fitting, or a dry/shifted P-trap, is the most common immediate cause.
  • Can I fix this without a plumber?
    Often yes — locating and reseating a fitting or refilling the trap fixes it. Call a pro if you find leaks you can’t stop or if the smell persists.
  • How long before the smell goes away after fixing it?
    If the source is corrected, the smell should fade within minutes to a few hours as trapped air clears and affected surfaces are ventilated.

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