Skip to main content

Why does my toilet bubble?

| Michael Quinn

There are several reasons your toilet may bubble, whether it’s from a build-up of pressure or a blockage in the drainage system. We have outlined the most common reasons why your toilet may be bubbling.

Common causes of a bubbling toilet:

  • A blocked drain
  • A build-up of pressure
  • A single pipe facilitating multiple drains
  • A clogged toilet
  • 空气准入问题
  • A build-up of sediment
A photo of a toilet about to be unblocked using a plunger
Unblocking your toilet with a plunger may help.

What’s the cause of a bubbling toilet?

If your toilet is bubbling, it could be a sign that your drainage system isn’t working correctly. When a single pipe is facilitating multiple drains simultaneously – in some cases, the bath, shower, sink, and toilet, this can cause bubbling.

If a blockage occurs in one of these drains, it can cause your toilet to bubble, likewise with your shower drains. So, if you have noticed your toilet bubbling while you’re taking a shower, it could be that your pipe fixtures are struggling with a blockage (or partial blockage) and are, therefore, taking significantly longer to drain.

Why your toilet may be bubbling.

One of the easiest ways to stop your toilet from bubbling is to determine if the blockage in your drainage system is minor or severe. Below are a few reasons why it may be bubbling

A clogged toilet.

If your toilet is blocked, try clearing it with a plunger. The act of plunging a toilet up and down creates a strong suction with force strong enough to remove the clog and successfully clear the blockage. Alternatively, you canread our article entitled 'how to clear a blocked toilet drain' for more information.


Air admittance valve (also known as a durgo valve) or venting issues in the drainage system can cause strange noises as well as the water level in your toilet to rise. Air admittance issues can lead to bubbling and gurgling to come from your toilet.

To see if it’s an air admittance problem, remove the valve and if your toilet flushes normally, your valve is the problem and will need replacing. Your valve is usually located next to the toilet or in the loft (at the top of the vertical pipe).

A build-up of sediment.

If there is limescale forming at the back or bottom of your toilet, it's likely to be a drainage issue. If you notice scale build-up in the u-bend, it could be a partial blockage. To fix this, you could remove the pan connecter (90-degree pipe) off the back of your toilet to free the blockage – but make sure you turn the water off and have a bucket to hand and to wear PPE if attempting to do this.

However, sediment built up in the tank due to iron, calcium, or magnesium in the water is more likely a plumbing issue.

Professional drain clearance from ASL Limited.

In some cases, the cause of a bubbling toilet may be caused by a blockage that requires professional clearance. If you are still experiencing bubbling problems and the solutions above did not work, contact our team at ASL and we will provide a solution.

Don’t delay we can help you today!

Call0800 181 684for all your drainage needs.

Our HQ is based in Guildford, but we cover the whole of Surrey, Parts of Berkshire, Hampshire, West Sussex and South West London.

See the map below or our 'areas covered page' for our services reach and use our postcode checker.