Why Does the Sink Gurgle When I Turn the Water On?

Imagine it's laundry day, and you've separated the darks from the lights. You put in your first load and start the washing machine, and it begins to fill as normal. A few minutes later, as the clothes start to wash, you hear a strange sound coming from the kitchen nearby. You might even hear the noise in the bathroom down the hall: a gurgling, bubbling sound coming from the drain. It's more than just an unsettling noise.

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If your sink gurgles when the water is on, it could be a sign your plumbing system is in trouble. It's best to address the issue sooner rather than later, and here's why.

Where the Gurgling is Coming From

To understand why your sink gurgles when the water is on, you need to know the basics of how your plumbing system works. Your plumbing system has three main parts:

Drain pipes. Drain pipes move water from your house to your septic system or the local municipal drain system. In most modern homes, they're made from PVC, ABS or copper. These pipes are all positioned so they slope slightly downward, letting gravity carry water out of the home.

P-trap. The p-trap is a U-shaped pipe found underneath any sink in your home. These pipes always hold a small amount of water in the bend to act as a barrier, blocking sewer gases from coming up through the drain.

Plumbing vent. The plumbing vent is a pipe that runs up through the walls and out of the roof. It resembles the open end of a straw. This vent helps equalize the pressure inside your pipes, allowing water to flow freely.

During the drain cycle of your washing machine, gallons of water move through the drain pipe in a short amount of time, which creates a vacuum. If your pipes are working as they should, air is pulled in through the plumbing vent to fill the vacuum and the water flows freely.

If your vent has a clog or gets blocked by leaves or other debris, the system won't be able to get enough air. Instead, the pipes will pull air from the closest opening, usually a nearby sink or even your shower or toilet. The gurgling noise is air moving through the water in the p-trap.

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Is This a Plumbing Issue, or Is It Harmless?

The gurgling noise is a plumbing issue, and like all plumbing problems, it should never be considered harmless. The noise won't damage your system, but the issue behind it could require a costly repair the longer you wait. It's important to contact a plumber to have the system inspected while the problem is still just a noise.

Here are some issues you might experience if you ignore the gurgling for too long.

Exposure to Sewer Gases

The gurgling noise indicates that the water inside the p-trap is being disturbed and even siphoned out due to the pressure inside your plumbing pipes. When this water is gone, there's nothing to stop the sewer gases from entering your home. These gases include methane, ammonia and carbon dioxide. Exposure can cause headaches, dizziness, nausea and drowsiness and may also lead to a persistent unpleasant odor.

Backups and Flooding

A gurgling noise is just the first warning sign. If the blockage continues or gets worse, the water from your washing machine may have nowhere to go. Eventually, the water will start to back up in your drains, and soapy, dirty laundry water will be on your floors. The overflow can cause significant damage to your walls, floors, subfloors and personal property.

Slow-Moving Drains

The blocked plumbing vent can affect your washing machine and eventually your entire plumbing system. You may start to notice the water in your sinks and shower drains much slower than normal. The same vacuum that causes the gurgling sounds also holds back water, preventing it from flowing freely.

Pressure on Your Plumbing System

The constant pressure inside your plumbing system stresses the seals and joints of your pipes. Over time, this pressure can lead to leaks and even burst pipes, causing widespread damage.

If your sink gurgles when the water is on, it could be an issue with your plumbing system. Now you know why this is happening and what you should do.