There Is a Gurgling Sound in the Kitchen Sink When the Shower Is Running

Gurgling coming from any of your plumbing fixtures is a sign of a blockage, but not necessarily one in the drain. The blockage is more likely in the vents that supply air to the drains, and the sound you hear is that of air passing through the drain from which you hear the gurgling. This can develop into an unhygienic situation if there's enough negative pressure in the pipes to empty the sink P-trap.

Gurgling from Negative Pressure

When a fixture's vent is blocked or improperly installed, the fixture doesn't drain quickly. That's because the water creates negative pressure in the pipes that actually impedes its progress. The effect is the same as filling a drinking straw with water and then covering one end with your finger; the water won't flow out the other end. In the case of a drain pipe, the force of suction pulls on the water seal in any P-trap connected to it, eventually breaking that seal and allowing air to rush in. The bubbling of the water as air passes through it creates the gurgling sound you hear. It's the same gurgling you hear when you pour water out of a bottle.

The Drain/Waste/Vent System

The main artery in a home's drain, waste and vent system is the main soil stack, which is a 3- or 4-inch pipe that runs vertically from the highest bathroom in the house to the outgoing sewer or septic pipe. It connects to the main vent stack, a 2- or 3-inch pipe which extends through the roof. All the plumbing fixtures connect to the main stack, and each fixture must have an individual connection to the vent stack. The plumbing code has strict requirements for the size and placement of each vent relative to the trap it services. If the vent is undersized, too far from the trap or simply blocked, negative pressure can develop.

Long- Vs. Short-Term Problem

If your kitchen sink has been gurgling when the shower drains for as long as you can remember, there's a good chance that the plumbing vents are undersized or installed incorrectly. You should be able to solve the problem by retrofitting the vents on one or both of the fixtures, and the first step would be a consultation with a licensed plumber. If the problem is a more recent one, on the other hand, a blockage may have developed. The blockage may even be in the drain line, because the sink and shower may be connected by an oversized drain line that also serves as a vent -- a configuration called wet venting.

Clearing Blockages

Without the ability to see behind the walls, you can't be sure what the drainage system looks like, so start by clearing and plunging the shower drain. If the shower and sink are connected by a wet vent that's blocked, and you clear the blockage, the gurgling will stop. If clearing the drain has no effect on the gurgling, then it's time to suspect a blocked or undersized vent. The blockage may be in the main vent stack. To clear the main stack, climb on the roof, clear debris from the vent opening and spray water down the vent from a garden hose. If this has no effect, you may need to consult with a plumber.

About the Author

Chris Deziel


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