Quick Answer:
If you come home after a long trip and see bubbles in a sink or hear gurgling, it’s often not a failed or vanishing trap. The most common cause is the trap losing its prime through slow evaporation or air movement in the drain system. The simple first fix is to refill the sink and drain to re‑prime the trap; that usually stops the bubbling and any sewer smell if it was caused by an empty trap.
Why This Happens
- Traps hold a small water seal. In dry conditions or with long gaps between use, that water can evaporate and allow sewer gas or air to move through the drain, producing bubbles or gurgling.
- Other fixtures or appliances on the same drain line can push air back through the pipes. For example, a washing machine or dishwasher moving water can cause short air reversals and sounds. You may recognize similar symptoms to Sink gurgles when washer drains in those situations.
- Partial blockages or slow venting can also cause strange refilling behavior or bubbling as water and air try to move past obstructions.
- Occasionally, noises come from behind walls where a vent or drain line runs; if you hear continuous or loud gurgling away from fixtures, think about a hidden line issue like **Gurgling from wall cavity**.
Step-by-Step What to Do
Step 1 — Do a quick visual check
- Look for standing water, leaks, or obvious damage under the sink and around fixtures.
- Smell briefly: a faint sewer smell that disappears after adding water is a sign the trap had dried.
Step 2 — Re‑prime the trap (fill and drain)
- Fill the sink basin with a few inches of water. Let it sit for a minute.
- Then drain it normally. The act of filling and draining refills the trap and restores the water seal.
- If you have a double sink, repeat on the other side and run a little water in nearby fixtures (toilets, tubs) to balance the system.
Step 3 — Run other fixtures briefly
- Run a sink, shower, or flush a toilet to see if the bubbling returns. That helps reveal whether the issue is isolated or affects the whole branch of plumbing.
- Note any correlation with appliance cycles (washer, dishwasher) and whether the sound or bubbles happen only during those times.
Step 4 — Look for persistent signs
- If bubbling continues after re‑priming, check for slow drainage or gurgling that suggests a partial clog or venting problem.
- Keep track of when it happens and where — this information helps a pro diagnose the cause.
What Not to Do
- Do not ignore the problem if odors persist — a lingering sewer smell can indicate a real plumbing or venting issue that needs attention.
- Do not pour large amounts of harsh chemicals down the drain in an attempt to “fix” gurgling; they can damage pipes or fixtures and usually won’t fix vent problems.
- Do not assume every post‑vacation bubble is harmless; use the re‑priming step first, then monitor.
When to Call a Professional
- Call a plumber if bubbling or sewer odor continues after you’ve refilled the trap and run nearby fixtures.
- Contact a pro if multiple fixtures gurgle, water backs up, or you notice slow drainage—these can be signs of blockages, broken vents, or line damage.
- Hire a professional if you detect leaks, persistent odors, or gurgling from inside walls or ceilings; those situations can indicate hidden leaks or vent issues that need inspection.
Safety Notes
- If you smell a strong sewer gas odor, ventilate the area and avoid using open flames until the source is found. Sewer gas can contain combustible gases in rare cases.
- Don’t stick your hand deep into a drain. Use tools like a plunger or a drain snake safely; if you’re unsure, call a professional.
- When working under a sink, support the cabinet and watch for sharp pipe edges and hot water lines.
Common Homeowner Questions
- Why did this happen only after my trip? Short answer: the trap likely lost water over time. Re‑priming usually fixes it.
- Will boiling water help? A small amount of hot water can help dislodge light debris, but don’t pour boiling water into plastic pipes or near fixtures that can be damaged.
- Can I prevent it? Run water in seldom‑used sinks before long trips or pour a small cup of mineral oil into the trap to slow evaporation for long absences.