Why Does My Toilet Gurgle When I Shower? 3 Causes and What to Do About Them

You hop in the shower for what should be a relaxing experience, but then you quickly find yourself asking, why does my toilet gurgle when I shower? What seems like nothing more than a minor nuisance can actually be a dangerous plumbing issue. Figuring out the underlying cause and getting a fix in place should be at the top of your homeowner’s to-do list.

1. Clogged Vent Stack

The most likely reason that your toilet gurgles when you shower is a clog in the vent stack, which is the vent that travels through your home and exits through your roof. This vent introduces air into your plumbing system to neutralize pressure caused by water entering your drains. If it gets clogged, that air has nowhere to go but back through your fixtures. The escaping air causes the bubbling in your toilet.

The Solution

Luckily, there’s an easy solution: clear the blockage in the vent stack. It’s best to call a local plumber for this fix, as it often involves getting up on the roof and snaking the vent from the top.

If the problem occurs only in winter, it could be due to ice or snow blocking the vent stack. In that case, you can try clearing the vent stack blockage yourself by running hot water for a few minutes in an upstairs shower or tub. The steam from the water will travel up the vent stack and slowly melt the blockage. Once you’ve dealt with the initial problem, have a roofer install a proper cap over the vent to prevent the issue from recurring.

2. Damaged Air Admittance Valve (AAV)

In older homes or add-ons, your bathroom may not be connected to the vent stack and instead utilizes dedicated air admittance valves (AAVs) to introduce air from your living space into the drains serving individual fixtures. AAVs last for around a decade before they start to fail. With a damaged or failing AAV, air pressure can build up in your plumbing, causing those pesky toilet noises.

The Solution

It’s possible to replace a malfunctioning AAV yourself if you have a replacement valve, a hacksaw, PVC primer, and cement. However, it’s best to have a licensed plumber come to ensure a proper installation and prevent the problem from happening again. AAVs keep dangerous sewer gases out of your home. This type of toilet repair costs under $150, on average, so the cost of your safety is worth it.

3. Pressure Created by Sump Pump

Drains in basement bathrooms usually feed into sump pumps, which collect wastewater and then pump it up into your main sewer line. When the sump pump turns on, it can create some negative pressure in your pipes, which can create a gurgling noise beyond the P-trap under your toilet.

The Solution

Pay close attention to the toilet while your shower is running. If you hear gurgling deeper in the pipes, you may not have an issue. If you see air bubbles coming up from your toilet, replace the AAV or hire a professional plumber to replace it for you.

When to Call a Pro

If you’re able to find the underlying issue, it’s possible to DIY a solution, either by thawing ice or snow that’s blocking your vent stack or by replacing malfunctioning air admittance valves. If you’re uncomfortable with or inexperienced in replacing PVC components, consider hiring a professional to ensure the job is done safely.

You should also call a professional if you can’t find the source of the issue or if fixing it requires accessing your roof, especially in the winter. Licensed plumbers can use proper safety equipment or even access the vent stack without roof access, and they’ll be able to identify the underlying problem to ensure you don’t experience gurgling or escaping sewer gases in the future.

How to Prevent Toilet Gurgling

There are several steps you can take to prevent gurgling from your toilet when showering, which will also help keep sewer gases out of your home.

• Make sure your vent stack is covered: Your vent stack should be covered to prevent water, debris, and animals from getting inside. Have a roofer install a screen and cap to keep it clear.

• Stay ahead of AAV replacements: Replace your AAVs every 5 to 10 years to ensure the seals are all working as they should.

• Have annual plumbing inspections done: Annual plumbing inspections will identify problems with your vent stack and AAVs before they lead to more severe issues, and they’ll also catch other issues that could cause further problems down the road.