Drain or toilet gurgling? Causes and solution

Water flowing away pushes air ahead of it and draws air behind it. In a properly working drain, that air can escape freely via the vent pipe that extends above the roof, or air enters via an air admittance valve. If that doesn't work, the air forces itself through the water in a trap or in the toilet bowl. You hear that as gurgling.

Why does a drain gurgle?

A partial blockage

This is the most common cause. The water still drains, but more slowly, and the air has to squeeze past the narrowing. If one drain gurgles, the problem is usually nearby. If several drains gurgle, it's further down the pipe.

A blocked or missing vent

Leaves or a bird's nest in the vent pipe, or a drain installed during renovation without proper ventilation: the air cannot escape and goes through the water in the traps. A defective air admittance valve, the valve that lets air into the drain, can also cause gurgling.

A lot of water at once

A washing machine or dishwasher that drains quickly, or a bath that empties in one go, displaces a lot of air. A slight gurgle after a full bath can be harmless. If it gets worse or you suddenly hear it during normal use, it's a warning sign.

Heavy rain

In many older neighbourhoods, rainwater and wastewater go through the same sewer. During heavy rainfall, that sewer can temporarily fill up, causing air and water to push back and a drain to start gurgling. If it only happens during heavy rain, the cause isn't necessarily in your own pipe.

Subsidence

In a subsided section of pipe, water remains standing where air can't pass. This often goes hand in hand with recurring blockages. Read more about a subsided sewer or roots in the sewer.

The toilet is gurgling: what does that mean?

The toilet has the largest drain in the house and is usually closest to the soil stack or sewer. If the toilet gurgles when you use the shower, washbasin or washing machine, there's often something in the shared drain further along. The water from the other appliance then pushes the air back via the toilet.

Does the toilet gurgle mainly during flushing itself, and does the water stand higher than normal in the bowl afterwards, or does it drop very low? Then there's probably a partial blockage in the toilet drain. In the article solving a toilet blockage you can read what you can do yourself.

Step-by-step plan for a gurgling drain

1. Note what gurgles and when. Which drain, and when using which appliance?
2. Test the other drains. Do they drain quickly, or slowly too?
3. Only one drain gurgling? Clean the trap and try a plunger. For the kitchen or shower, follow the steps in kitchen drain blocked or shower drain blocked.
4. Is the toilet gurgling and is the water level high? Use a toilet plunger and don't flush again whilst the water level is high.
5. Does it only happen during heavy rain? Keep an eye on it. If water comes up from a drain, use as little water as possible until the downpour has passed.
6. Are several drains gurgling, or does it keep coming back? Then professional unblocking is needed, possibly followed by a camera inspection.

Why you shouldn't ignore gurgling

A gurgling drain is rarely immediately dangerous, but it is a warning. A partial blockage usually gets gradually worse, until the water comes up at an inconvenient moment. Moreover, the gurgling can empty the traps, allowing sewer smell in the house. By dealing with it early, you prevent water damage.

In The Hague and surrounding area: see drain unblocking The Hague centre; in Delft: drain unblocking Delft.