Floor drain gurgles at night

Quick Answer:

If you hear a gurgling noise coming from a floor drain overnight, it is often an air movement or trap issue rather than an immediate gas leak. Run a few simple checks: run the drain fixture by itself and then with another nearby fixture, watch nearby trap water levels, and listen at the drain opening to tell whether water is being sucked away or pushed back. If the sound keeps returning or several fixtures are affected, have a licensed plumber inspect venting and the main line.

Why This Happens

• Traps losing or gaining water: A dry or partially emptied trap can let air move through the drain and cause gurgling.
• Vent problems: Blocked or restricted vents can prevent air from flowing normally, so air is pulled through traps when fixtures drain.
• Partial blockages: A restriction in the drain or main line can cause air and water to force each other, producing bubbling or gurgles.
• Intermittent loads: Appliances or other fixtures used at night (like a timed sump or an off-hour washer cycle) can change flow and trigger sounds.

Step-by-Step What to Do

1. Start by listening and noting timing

• Listen at the drain when you hear the noise. Is it happening only at night or anytime there is flow?
• Note whether the sound is a sucking or bubbling push. Sucking suggests air being pulled past a trap; bubbling/pushback suggests water or air being forced up through a trap.

2. Run the triggering fixture alone

• Turn on the fixture that seems to trigger the noise (for example a basement floor drain) by itself for a short test drain.
• Watch the nearby trap seals (toilet, sink P-trap, floor drain trap) for visible movement or loss of water.

3. Run the triggering fixture with another fixture

• While the first fixture is draining, run a second nearby fixture (sink or tub) and see whether the gurgling changes or stops.
• If the gurgle disappears when another fixture is open, that points toward a venting or pressure-equalization issue.

4. Check trap water levels

• Look for water level drop or bubbles in traps near the drain. If trap water moves or drains, the trap seal can be compromised and allow odors in.
• If a trap is dry, pour a small bucket of water into the drain to refill the trap and see if the gurgling stops temporarily.

5. Note patterns and related causes

• If the gurgling started after work in the home, consider renovation-related changes — see Gurgling started after remodel.
• If the washer or another appliance is nearby, test during a wash cycle — see Gurgling when washer drains.

What Not to Do

• Don’t pour harsh chemical drain cleaners down the drain. They won’t fix venting or main-line problems and can damage pipes and traps.
• Don’t cap or seal roof vents or other vent openings on your own to try to stop the sound; that can create pressure problems and unsafe sewer gas conditions.
• If multiple fixtures are affected, don’t assume it’s a single local clog — a professional should check venting and main-line conditions rather than you chasing each drain.

When to Call a Professional

• Call a licensed plumber if the gurgling keeps returning after simple tests, if multiple fixtures are involved, or if traps are repeatedly losing water.
• Ask the plumber to evaluate venting, test for partial main-line blockages, and inspect trap seals. A camera inspection of the drain line may be needed to find a hidden obstruction.
• If you ever smell strong sewer gas or suspect a hazardous leak, contact a professional immediately and ventilate the area.

Safety Notes

• Work in well-ventilated areas if you need to check floor drains.
• Avoid chemical cleaners; use water to refill traps. Chemicals can splash and cause skin or respiratory irritation.
• If you must access roof vents, don’t climb roofs alone and use proper fall protection — better to have a pro handle vent inspections if you’re not experienced.

Common Homeowner Questions

• Will the gurgling let sewer gas into my home? Not usually immediately; gurgling often means air movement. If traps are losing water, though, odor entry becomes possible and needs attention.
• Can I fix this by pouring water down the drain? Temporary yes—refilling a trap can stop noise short-term—but it won’t fix venting or line problems that recur.
• Is this an emergency? No in most cases, but if you smell sewer gas strongly or many fixtures are affected, have a plumber inspect promptly.

For more related articles, see the Gurgling Sounds From Drains or Fixtures hub.