Last updated: April 22, 2022 at 15:12 pm
A bath that gurgles when you flush your toilet can be annoying. It might also make you worry that there is something wrong with your plumbing as your bath and your toilet should not be linked, should they?
Rest assured that gurgling from your bathtub when you flush your toilet is rarely a sign of any serious problem. Depending on how confident you are at tackling minor plumbing issues, you may even be able to fix it yourself.
Plumbing Basics
Before we begin to look at causes and solutions, it’s important you understand the basics of how the plumbing in your bathroom works. If you have already got a fair bit of plumbing knowledge from previous projects, you can skip straight to solutions.
There are several components in the plumbing system in most homes, but for this article, we’re going to look at the drains, vents, and the P trap.
The Drains
Naturally, all your sinks, toilets, showers, and baths have small drainpipes that link them to the main drainpipe for the home. There is no pump or any device that causes the water to drain.
Water is carried away by gravity only and keeps going until it leaves your home and arrives at the main neighbourhood sewerage system.
The Vents
As well as water, your plumbing system also must include air to normalise the pressure inside the pipes. To allow air into the system, the drains are connected to a large vent that emerges from your home on the roof. When you flush your toilet, air will come down from the vent and help balance the pressure.
The waste vents also have a secondary role which is to release any build-up of sewer gases inside the pipes.
The P-Trap
As explained above, one job of the vents is to carry away unpleasant-smelling sewer gases and release them on the roof where they won’t affect the smell around your home.
However, the question is, why do the gases always go out through the roof rather than just entering your home through the toilet? After all, the toilet is a much near exit for the gas.
The easiest way to understand how the P Trap works is to look under your sink. All sinks have a U-shaped section, and water sits at the bottom of the U. The water is heavier than air and prevents the air from coming back into the home.
Your toilet doesn’t have a P-Trap, but your toilet’s plumbing works in the same way. You can see this as there is always water at the bottom of your toilet.
How to Fix a Gurgling Bath When Toilet Flushed
Now you understand how your plumbing works, let’s look at possible fixes for the gurgling sound.
1. Consider Widening Your Pipes
Some homes are fitted with pipes that are simply too narrow for toilet paper, or possibly you’ve been flushing paper towels and other items that the pipes are not built for. If you’re flushing anything other than toilet paper, you should stop doing this as it is not only bad for your internal plumbing but the town sewerage system.
If you are only flushing toilet paper and are still having problems, then you could consider replacing your pipes with wider ones.
You’d need to do your research into how to replace the pipes and decide if this is a project you would like to attempt yourself. If not, then call in a couple of plumbers and get quotes for the job.
If you don’t want to replace your pipes, you could try reducing the water pressure of your toilet’s flush. You can do this by placing a brick or other heavy object into the cistern and then testing to see if the gurgle has gone.
2. Try Using a Plunger to Clear Waste from the System
Waste can build up and harden on the inner walls of your pipes which prevents water and air from getting through. You might be able to clear some of the waste with a vigorous plunging. First, you’ll need to tape over the plughole in your bath and sink.
Then use a plunger to plunge your toilet for a few minutes. Plunging will serve two purposes; it will clear waste from the lining of the pipes and remove any excess air from the system.
Once you have plunged the toilet, remove the tape from the drains and try flushing the toilet again. Hopefully, the noise will be gone.
3. Use Drain Cleaner
If plunging hasn’t worked, you could try using a chemical to clear any blockages. There are many products on the market, so you’ll be able to pick one up at the supermarket.
Pour it down the toilet and leave it for the time specified on the label. You would usually pour cold water down, but hot water can help dislodge additional contaminants.
Top Tip!
If your bath is also draining slowly, it might be worth buying enough to treat the drain at the same time.
4. Use a Wire Hanger
Untwist the hanger, so it becomes a straight piece of wire. Cover the wire in old rags to prevent it from damaging the toilet. Gently guide the wire into your toilet and through the waste pipe until you hopefully find a blockage.
If you do, twist the hanger around and apply pressure to clear it. Once this is done, flush to remove the blockage altogether.
Also read: 4 Best Silent Extractor Fans
5. Clear Any Clogs or Blockages of the Vent
Clear the Vent Covering
The vent needs to be clear and free of debris to provide the correct amount of air into the system when you flush the toilet. If it is clogged, the pressure will not be equal, and this can cause a gurgling noise. Essentially, the air is trying to enter the pipes but can’t, so it picks the nearest access point. In this case, it’s the plughole in your bath.
The tricky part is that the vent runs through your whole house and the blockage could be anywhere. However, the easiest place to start is where it leaves the house. The vent leaves your home on the roof, so you’ll need a solid ladder and someone to hold it steady while you climb up.
The vent should have a screen or some other mesh over it to stop leaves, moss, and other debris from falling in. Firstly, clean this mesh thoroughly and see if it solves your issue.
Top Tip! It will not fix this issue, but if you’re on the roof, you should also look at your guttering. It can also fill with leaves and moss, and if it becomes blocked, then the water can’t drain away when it rains. If this happens for long enough, water can get into your home and cause damage.
Flush the System
If cleaning the mesh didn’t do the trick, the next step is to try and clear any blockages with water. You’ll need to buy or borrow a hose long enough to reach the roof vent.
If the blockage is further in and is not too solid, you should be able to clear it by pouring water through the hose. Start slowly; if the blockage does not clear, you don’t want to flood your roof and damage it.
If the water continues to flow normally, increase the pressure a little at a time and run water into the vent for a few minutes. Then, check if the gurgling still exists.
Use a Plumbing Snake
A plumbing snake is a flexible drill bit attached to a long wire and handle. When the snake is inserted into the vent and the handle is turned, it will rotate through the pipe and clear any hard blockages. If you don’t meet any blockages, then the problem is likely further into your system than you can reach.
Unfortunately, you’ll need to call in a professional at this point. They may need to use an auger (snake) with an extra-long wire and camera on the end so you can see exactly where the blockage is.
Other Causes
We’ve covered the most common causes and fixes, but there are other possibilities. It may be that your plumbing is old and that parts of it are rusted or corroded, letting air into the system. You would need to get a plumber in to inspect your system and confirm if this is the case.
If you have large trees near your home, it’s possible for the roots to clog the drains as they enter the neighbourhood system. This would require professional help but thankfully, it’s not a common problem. You should rule out everything else listed here before you investigate the sewer pipes.
Conclusion
A gurgling noise from the bath when flushing your toilet is annoying but rarely a huge problem. Approach the issue methodically and try each step-in turn. Most of the time, the sixes above will resolve the issue without you having to spend money on a plumber.
However, know your abilities and ask for professional assistance if in doubt.
