What causes a gurgling sound when a bathtub or sink drains?
Wednesday, June 20, 2018
The gurgling is most likely to occur when the tub or sink has been filled with water and then drained. It is caused by the drain releasing air displaced by the volume of water draining and is is comparable to what happens when you turn a soda bottle upside down to drain it, as bubbles of air surge up to the top of the bottle with a “glug-glug” sound as it struggles to empty itself.
By far the loudest and most annoying gurgling sounds we find are at spa or garden tubs with plastic (PVC or ABS) drain piping that have inadequate venting. The overflow drain pipe seems to amplify the sound.
We recommend that you have a plumber evaluate the problem for you and recommend a solution. Here’s our short list of things that could be causing your problem:
- Obstruction in vent pipe through roof.
- Vent pipe too far from drain or no venting for fixture.
- Partially blocked drain pipe.
Adding an air admittance valve will sometimes solve the gurgling problem. But removing any obstructions in the vent or drain piping is the easiest and best solution most of the time.
Gurgling sound at the water heater is a different problem. See our blog post Why is my water heater making strange (rumbling, gurgling, knocking or banging) noises? for that.
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