Why Is My Bathroom Sink Gurgling? (How to Fix)

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Do you hear a gurgling sound from your bathroom sink? Gurgling can be heard from the sink when water drains through the flange, flushing the toilet, or even when the washing machine water drains. It is an indication of improper ventilation in the drain pipes.

If you’re hearing such a sound, then it’s recommended to fix this issue as soon as possible before the problem gets bigger.

In this guide, I have tried to keep everything simple so that a homeowner with no knowledge about plumbing can easily understand and take necessary actions. This post will address:

  • Some common causes of bathroom sink gurgling.
  • How to stop gurgling in bathroom sink?

Here’s Why Your Bathroom’s Sink Gurgle:

The most common problem that causes gurgling sink is blocked vent pipe. There must be some blockage in your plumbing ventilation system that is causing an improper flow of water. This blockage can occur when small debris is released into the drain, overtime forms clog, and blocks the pipe system. Besides, incorrect or illegal installation of plumbing traps can cause gurgling in the bathroom sink.

Let’s understand what vented pipe means.

When water is released, the vent pipe is intended to let the air in. This ensures that the water can flow steadily without causing pressure issues. It allows the water to flow smoothly without creating a gurgling sound.

To be much clear about this, you can try out an experiment.

demo experiment to check how gurgling happens
  • Take a bottle filled with water. Hold the bottle upside down, allowing the water to flow through the exit hole. You will notice a gurgling sound coming from the bottle. Here gurgling is air bubbles flowing through the water bottle.
  • Now, take another bottle. But this time, create a vent by introducing a small hole in the bottle. Again, hold the bottle upside down and allow the water flow. You will notice, water will flow steadily without making that gurgling sound.

Why is it so? That’s because introducing a small hole allowed the air in, which made water flow without any disturbance or gurgling.

Signs Of Blocked Vent Pipe

Most blockages in vents are caused by collecting dust, hair, and other debris. Here are some signs of blocked sewer vents:

  • Slow Draining of Sink Water: Over time waste and small debris released in to the drain gets collected and form clog. Thus, reduces the size of the drain, causing slow draining of sink water.
  • Toilet Flush Slowly: Vent clog caused by the hair, debris, etc can cause toilet to flush slowly.
  • Water Overflow: Blockage in vent pipe can restrict the flow of water. This makes the water return back causing overflow.
  • Smell from Sink: The junk in the drain pipe can rote when vents are blocked for a long time. It will stinks like rotten eggs when water runs. Sewer gases like ammonia and hydrogen sulfide can be toxic and produce a foul smell like rotten eggs. According to Wikipedia, Methane is also a component of the sewer gas that can cause harmful impacts on health like headaches, nausea, and dizziness. If you notice such symptoms, then probably you’re inhaling methane gas.

How to Fix a Gurgling Bathroom Sink? (Unclog Vent Pipe)

clog in pipe vent infographic

Using A Plunger

Weaker clogs in the vent pipes can be easily pulled out using a plunger. I will recommend you first use a plunger to clear the clog present in the vent pipe.

If you are unsure about what is a plunger, take this note. A plunger is a tool that has a rubber cap on the end that works effectively to clear a blocked pipe in a sink or toilet.

How to Use A Plunger to Unclog Vent Pipe:

  1. First, you need to have an inch of standing water in the sink. You can use a sink stopper to stop the draining of water.
  2. Next, To get a better seal, apply a little petroleum jelly to the plunger cup.
  3. Remove the stopper. Then, place the plunger on the drain and start plunging in and out vigorously until water drains steadily.
  4. Repeat this process if needed.

Most of the time, this process works effectively and unclogs the vent pipe. But in the case of a larger pipe system, it may not work. There are a few other methods that you can try.

Using A Drain Auger

Drain augers also known as drain snakes are tools specially designed to clear clogs in vent pipes. This tool appears like a snake that can reach deep down the drain through the pipes as a real snake does. That’s why it is called drain snakes.

This tool is flexible and long enough to reach deep into the drain and clear the clogs causing a blockage in the vent system. If you plan to use a drain auger, don’t forget to get the correct cable size.

Below is a chart that guides about pipe sizes and recommended cable sizes:

Drain TypeVent Pipe SizeRecommended Cable Size
BATHTUB1-1/2″ — 2″1/4″ OR 5/16″
SHOWERS2″ — 3″5/16″, 3/8″ OR 13/32″
FLOOR DRAIN3″ — 4″3/8″, 13/32″, 1/2″, 5/8″, 3/4″ OR 0.55″
FLOOR DRAIN4″ — 5″1/2″, 5/8″, 3/4″, 0.55″ OR 0.66″
FLOOR DRAIN6″ — 8″5/8″ (NON ROOTS), 3/4″ OR 0.66″

Using Clog Removing Chemicals

Another way of cleaning a clogged drain is by using chemical clog removing products. Most people have a misconception that any clog remover will do the work, but that isn’t true.

There are different drain cleaners based on the severity of clogs. For instance, a drain cleaning chemical used for a slow-flowing drain won’t work for a complete blockage.

For unclogging vent pipes, I will recommend using Max Gel Clog Remover by Drano. This thick gel helps in dissolving clog build-up such as hair, soap scum, grease, etc.

How to Use Drano Max Gel Clog Remover:

  1. First, open it carefully by psuing the childproof cap and turn the cap counterclockwise.
  2. Then, gently pour 16oz of the liquid gel over the drain. Avoid squeezing the bottle as it might come in contact with your skin.
  3. Now, wait for 15 minutes and let the chemical do its work. (Leave it Overnight for better result)
  4. Finally, flush the drain with hot water and its done.

*Safety Precautions to Take While Using Clog Removing Chemicals*

  • Read the instructions properly before using.
  • Take safety measures by wearing gloves and eye protection.
  • Do not squeez or splash the chemical.
  • Do not clear toilet clog using clog removing products.
  • Flush the drain properly after application.
  • Do not mix clog remover with other cleaning products.

Illegal Plumbing Trap Can Cause Sink Gurgling

Sometimes installing the wrong type of plumbing trap can cause your bathroom sink to make a gurgling sound.

Generally, the “S” shaped plumbing traps are considered illegal because they aren’t vented and can suck the water out of the trap as the water flows down the drain, allowing sewer gas to enter your house.

That’s not a properly ventilated trap you should have installed.

So what’s the correct plumbing trap? “P” shaped plumbing traps are recommended. The curve in P-traps always maintains a water seal, which limits air and gases to move through the pipe. This prevents harmful sewer gases to enter your house.

What if I have an “S” trap? Is there anything we can do? Well, you can fix it with a replacement.

  • Replace whatever plumbing trap type by introducing a “T” fitting. And extend the pipe from the bottom of “T” towards the main drain line.
  • Then, extend the pipe from top of the “T” towards vent system in your house. If your house is not having a vent system, try extending a pipe to the roof.
  • Some country code allows you to place retrofitted mechanical vent, it allows air to come in that will break the vaccum on the slug of water and don’t let sewer gas enter.

Must Read | 14 Types of Traps In Plumbing by CivilJungle

Wrap Up

Fixing a blockage in your vent pipe requires effort. To be honest, fixing a blockage in the vent pipe has some risks like damaging the plumbing system. So the best possible solution is to ask for help from professionals who have previous experience in this work.

However, if there is a minor clog blocking the vent pipe, try a plunger. You only have to plunge in and out vigorously until water drains steadily. That’s something I will recommend to try on your own.

Besides, if you have the wrong type of plumbing trap installed in your house, it’s better to contact a professional to check what can be done to fix it. They can assist you better.

I hope you are now clear on why your bathroom sink is making a gurgling sound. If you have any query drop a comment, I will get back within 24 hours.


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