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Tub Drain Gurgles When Flushing Toilet

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Does your tub drain gurgle when you flush your toilet? Or do you hear a gurgling sound whenever you flush your time? Well, this can be disturbing, especially if you don't know where the problem is coming from.

A gurgling noise coming from your tub drain can be caused by a variety of different things. This article will go over some of the potential causes and what you can do to fix them. Keep reading.

What Causes the Toilet to Gurgle?

There are a few different things that could be causing your tub drain to gurgle when you flush the toilet.  Just like when flushing your toilet sink gurgles, the causes are all the same as when your tub drain gurgle when your toilet is flushed. These causes include:

What Causes the Toilet to Gurgle?
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Plumbing Vent System

One of the most common causes of a gurgling sound coming from your tub drain is that there is an issue with your vent pipe. The vent pipe allows the water in your plumbing system to flow smoothly. If there is a clog or leak in it, then the water will not flow as it should.

When there is no water in your plumbing pipes, air fills the pipes. All plumbing systems have vent systems that transfer air out through the roof. Obstruction in your plumbing vent system can cause bathroom drains to gurgle. Bathroom plumbing pipes are all connected to the same system.

When a connecting branch to a fixture group becomes clogged, you'll hear a gurgling sound. The proper function of each drain is connected because of the way the plumbing systems are designed.

Shower Drain P Trap

The p-trap is a U-shaped pipe located under the sink. This trap holds water in order to create a seal that prevents sewer gases from entering your home through the drain. The water also provides weight to keep the trap seal.

If there is not enough water in the p-trap, sewer gases can escape and cause your drain to gurgle. You can add more water by pouring some down the drain or simply filling a container with water and setting it into the p-trap until it is full.

Shower Drain P Trap
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Also, a gurgling drain can be caused by a shower drain that doesn't have a p trap. Maybe the p trap is busted, or the trap has been empty because the shower has been unused for long periods of time. You can test to see if you have a p trap or f it's busted by inserting a small wire or thread down into the drain.

When you pull the wire back up, you should find about 4-6 inches of water on the wire. This lets you know that you have a working p trap. If you don't find any water, then it's likely that the drainpipe is broken and needs to be repaired. Make sure you fix it immediately.

Problem With Sink Vent

One common cause of gurgling sounds is a problem with the sink vent. The sink vent is responsible for drawing any water and air out of the drain pipes so that the plumbing can run smoothly and efficiently. If this vent becomes clogged or damaged, it can cause gurgling in your drains.

One way to test this is to run water in the faucet while listening for gurgling sounds. If you're experiencing these sounds, then your sink vent may be clogged and needs to be cleared out. You can do this by using a plumbing snake or by simply cleaning it out yourself.

Narrow Drain Pipes

If you're experiencing gurgling drains when you flush your toilet, maybe your drain pipes are too narrow. This can create a suction effect that pulls air from the sewer line and causes your drains to gurgle. Some of the toilet waste inevitably gets stuck over the pipe walls.

With time, this waste starts to decompose, resulting in a hard clog. This won't directly clog your pipes but will make them incredibly narrower. So, when the slightest amount of water flows in, pressure builds, and air gurgles in your bathtub drain.

If you're lucky, your plunger might be able to push some of the hardened waste to widen the pipes. Make sure you close all your bathtub drains, sinks, or any other fixtures with rubber plugs. This way, all of your plunging forces would remain inside the pipes.

If the gurgling persists after 3-4 rounds of plunging, consider using a toilet auger. An auger is a long, flexible snake that can be used to clear hard clogs. A toilet auger shares the same principle as the regular drain auger but is equipped with a long arm to drive the wire deeper.

Use the auger carefully to avoid scratching your toilet bowl. The auger plastic shaft is curved to the end for this purpose. Therefore, you shouldn't push or pull the auger wire unless it's fully tucked into the plastic. Once you've removed the waste clog, flush down some drain cleaner to dissolve any remaining debris.

Old Cast Iron Pipes

Cast iron has been widely used in the plumbing system before the emergence of ABS and PVC pipes. Unlike its successors, cast iron has a corrosion tendency and is difficult to cut without professional help.

If your house was built before the 80s and you still have the old cast iron drain pipes, they're likely corroded and need to be replaced. You may notice some leakage in the joints or cracks in the pipes. In this case, you should call a professional plumber to have them replaced.

Blocked Sewer Line

If your tub drain gurgles when you flush the toilet, it's likely because there is a blockage in the main sewer line. This can be caused by waste buildup, tree roots, or other objects that become lodged in the pipe. You'll need to contact a professional plumber to clear the blockage and restore proper drainage.

How to Fix a Gurgling Toilet

How to Fix a Gurgling Toilet
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Plunge Your Toilet

For smaller, minor clogs, a toilet plunger that has an extension flange may work. The extension flange helps give the plunger a snugger better fit on the jet hole and the drain hole. Before placing the plunger on your toilet, make sure you don at least a face mask and gloves.

Slowly and carefully place the plunger over the drain hole. Push and pull the plunger up and down with consistent, even pressure. After about 30 seconds to a minute, flush your toilet to see if the gurgling has stopped.

Clear Venting System Clogs

One common reason toilets gurgle is because the home at s venting system is clogged. The venting system for a toilet runs from the toilet drain through the roof. This system helps remove sewer gases and keep your bathroom smelling fresh.

Obstruction in the plumbing vent lines can occur at the main vent stack, which is located on the roof. Most of the time, debris will fall from the vent opening and collect in an elbow in the ventilation system. Birds and small animals can climb in these vents, therefore, you'll need to clear this out to make the gurgling stop.

You can clear this out by using a garden hose or plumbing snake, as these will help remove any debris that is causing the obstruction. If you're unable to clear the obstruction, then you'll need to call a professional plumber for assistance. If you don’t want to be bothered with this problem you can do away with the venting system if you know how to vent a toilet without a vent.

FAQs on Why Your Bathtub Drain Gurgle When Toilet is Flushed

What causes a gurgling sound in bathtub when flushing toilet?

There are several possible causes for a gurgling sound in the bathtub when you flush the toilet, including debris buildup in the ventilation system, clogs or blockages in your plumbing pipes, and increased water pressure in your home.

Noise from shower drain when flushing toilet. Why?

Shower drain noise when flushing the toilet is usually caused by a clog or blockage in the pipes, which can create increased water pressure and cause gurgling sounds.

How can you permanently do away with the gurgling sound in your tub drain?

You can as well forget this problem once and for all by doing away with the old tub drain and the toilet if you suspect they may be the major cause. Make sure you shop for some of the best flushing toilets in the market to allow smooth flowing in your toilet.

Final Thought on Why Your Bathtub Drain Gurgle When Toilet is Flushed

There are a lot of problems that can make your bathtub drain gurgle when your toilet is flushed. Ignoring these gurgling noises can result in major setbacks, so it’s important to figure out what is causing the problem and take care of it as soon as possible.

In most cases, a simple drain cleaning will take care of the issue, but if the problem persists, you may need to call a professional plumber for help. If gurgling persists, then it's time to call a licensed and experienced plumber to take a look and find the root of the problem.



Kristina Perrin

Kristina Perrin

Kristina is an expert DIY home remodeler and mom to three. When she's not cooking or experimenting with new recipes, you can find her working on new home improvement projects or writing about her favorite kitchen appliances or DIY projects on Kitchen Infinity blog.

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