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:

1. Obstruction in vent pipe through roof.
2. Vent pipe too far from drain or no venting for fixture.
3. 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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Here’s links to a collection of our other blog posts about PLUMBING:

• How can I protect my pipes to keep them from bursting during a hard winter freeze in North Florida?

• Why is there sand in the bottom of my toilet tank?  

• What causes a gurgling sound when a bathtub or sink drains? 

• Are drop-in toilet bowl cleaner tablets safe? 

• What can I add to my septic tank to help it work better?

• What are the code requirements for layout of drain piping under sinks? 

• Why is there mold inside my toilet tank?  

• What are the pros and cons of a wall-mounted toilet?

• Which plumbing fixtures require water shut off valves in a home? 

• How can I tell if a house is connected to a septic tank system or sewer?

• Are plastic pipes (PVC, CPVC, and PEX) safe for drinking water? 

• What are the common problems to look for when the plumbing has been replaced in a house? 

• What's that powdery crust on the pipe connections at the water heater? 

• How can I tell what type of plumbing pipe I have? 

• What causes low water pressure in a house?

• Should I call a plumber or septic tank contractor when my septic tank backs up into the house? 

• How do I get rid of the sewer gas smell in my house?  

• What are the pipes on my roof? 

• Should I wrap the water heater with an insulation blanket? 

• My water bill went way up last month. How do I look for a leak?

• Why does the water have a rotten-egg smell in some empty houses? 

• Is it alright to disconnect the washing machine drain from the septic tank and divert it to the ground in the yard?

      Visit our PLUMBING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.