When your plumbing system works the way it should, it’s easy to forget all about it. But when a problem catches your attention, the plumbing becomes all you can think about until you resolve the issue.
If you’re experiencing toilet bubbling or bubbles in the toilet bowl when your bathtub drains, it could be a sign of a blockage or problem with your drainage system. Find out what causes a bubbling or gurgling toilet, how to troubleshoot the problem and when it’s time to call a professional.
What Causes Toilet Bubbles When the Tub Drains?
Your toilet bubbles when the bathtub drains because trapped air is being pushed back through the toilet instead of escaping through the vent pipe.
The toilet bubbling phenomenon can be linked to something called wet venting. In some bathroom drainage systems, several fixtures, including the bathtub, sink and toilet, can share sections of the same drainage and venting pipework.
The vent allows air to move through the drainage system and helps prevent pressure from building up as water flows away. If a blockage develops in the drain or vent, this airflow can be disrupted.
When the bathtub drains, air may then be forced through another fixture, causing the toilet to bubble or gurgle. You may also notice that your bathroom fixtures are slow to drain or that your toilet flushes more sluggishly than usual.
A bubbling toilet can therefore be caused by:
• A partial blockage in the drain
• A blocked or restricted vent pipe
• A blockage further down the drainage system
You may also notice slow-draining fixtures, a sink that gurgles when the tub drains, or a toilet that flushes sluggishly.
Partial blockage
A partial blockage is one of the most common causes of toilet bubbling. Hair, soap scum and other debris can build up inside the pipework, restricting the flow of water and air.
If the problem is limited to one bathroom, the blockage is more likely to be within the pipework serving those fixtures.
Clogged vent pipe
Your drainage system relies on vent pipes to regulate air pressure and allow sewer gases to escape. Leaves, debris or nesting material can sometimes block the vent, preventing air from moving through the system normally.
A blocked vent can cause your toilet to gurgle when flushing and may affect more than one fixture.
Main sewer line issue
If several fixtures or rooms are affected, the problem could be further down the drainage system.
A blockage in the main sewer line can be caused by a build-up of debris, unsuitable items being flushed, tree root ingress or damaged pipework. These problems can be more difficult to resolve and may require specialist equipment.
How to Troubleshoot Air Bubbles in the Toilet Bowl
The clog causing air bubbles in the toilet may be minor or quite severe. To help you determine how serious the problem is, follow these troubleshooting tips.
Clear the bathtub drain
Remove the strainer and clean any hair and soap scum and other visible debris. Then, insert a plumbing snake into the drain. This removes obstructions a foot or two down.
Plug the bathtub and fill it with a few inches of water. Release the plug, and as the water drains, keep an eye on the toilet. If the bubbling persists, you know the blockage is further down.
Clean further down the drain
Avoid repeatedly using chemical drain cleaners, as they can damage pipework and may make it more difficult for a professional to work on the blockage safely.
Instead, you can try using a longer plumbing auger to reach further into the pipework. As the toilet is also affected, plunging it with a suitable toilet plunger may help to dislodge a minor blockage.
If you have tried these steps and the bubbling continues, the blockage may be further down the drainage system. This is when it’s best to call in the drain unblocking professionals.
Clear the vent
If your effort to clear the plumbing doesn’t work, the blockage could be located in the vent. The main vent stack should exit through the roof. Pay a visit there, and you may discover leaves or other debris blocking the vent. However, accessing a roof-level vent can be dangerous, so you should not attempt this if it cannot be done safely.
Remove surface debris and spray water down the vent to help clear obstructions further down. If the vent overflows, use a plumbing auger to remove stubborn clogs. Once cleared, consider installing a protective screen over the plumbing vent to prevent a repeat occurrence.
Why Call a Professional to Fix the Situation
If your toilet continues to bubble after trying these troubleshooting steps, or the problem keeps returning, it’s best to have your drainage system checked by a professional.
You should contact a drainage specialist if:
• Your toilet continues to bubble or gurgle
• More than one fixture is affected
• Several drains are slow to empty
• You notice unpleasant drain smells
• Wastewater is backing up into your bath, sink or toilet
• You suspect a blockage further down the drainage system
• Your attempts to clear the blockage have not worked
A professional drain engineer has the specialist equipment and knowledge to locate the cause of the problem without causing further damage. In more complex cases, a CCTV drain survey can be used to inspect the pipework and identify issues such as blockages, tree root ingress or damaged pipes.
If your toilet is bubbling when your bathtub drains, Drain Doctor can help identify and resolve the problem.
Our experienced engineers provide professional drain unblocking and plumbing services across the UK, 24 hours a day, 365 days a year. Whether you have a blocked toilet, slow-draining bathtub or a more serious drainage problem, we have the expertise and equipment to help.
For help unclogging your toilet or freeing up a shower drain, contact Drain Doctor today or call us 24/7 on 0808 253 8514.