Why Unused Bathroom Smells Like Sewer After Use


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To keep their bathrooms smelling fresh, most people use air fresheners. To ensure a pleasant odor, candles or fragrances are occasionally burned or opened.

What should you do if your bathroom has a sewage odor? The shower drain, the Jacuzzi tub, the sink, and the toilet are all places to look. If the sink and toilet drains are gurgling and the water smells, you may have a major problem with the sewage system.

Having the smell of sewers in our home is not something pleasant at all, and it is not a fragrance we want to be around or breathe in daily.

There are many reasons why your unused bathroom might smell. They are either an issue with the shower drain, a cut vent pipe that is not installed properly on the toilet, or as a result loose seal or a broken seal. Additionally, it can be due to buildup in the sink overflow.

1. P-Trap

Why Unused Bathroom Smells Like Sewer After Use could be the p trap
The P Trap

It is not unusual to have an unused bathroom smell like sewer after use, and the smell most likely comes from the P-trap.

The P-trap is mainly the U-shaped pipe underneath the drain, and it is used mostly to keep sewer odors from coming into your bathroom.

The drain plumbing under your sink not only transports wastewater away from your home but also keeps hazardous sewer gases out.

When the drain remains unused for a prolonged period, the water in the P-traps evaporates, and the sewer odors then find their way into your home.

This is how it goes. When you run water through your sink, the wastewater passes via the drain and into either your septic tank or the public sewer line.

The sewage system can be accessed directly through your drain lines. Sewer gas would vent directly into your home if the P Trap was not kept full with water. Water traps must be installed in all drains in your home. Your toilet bowl contains water, and the floor beneath your bathtub has a P Trap.

When a drain is used, the water collects itself in the P-traps hence preventing sewer odors from coming into your home.

The only way to fix this problem is to run some water to create a seal within the P-traps.

This can be done very often to prevent the water in the P-traps from evaporation.

Using drain cleaners and household cleaning products will only mask the smell temporarily but won’t curb the smell permanently.

Pour a cup of vinegar and a quarter cup of baking soda down the drain and see what happens. Allow for a 15-minute rest period after mixing If the stink doesn’t go away after running the water.

You can as well run hot water through the drain for at least three minutes to clear it. Pour a couple of tablespoons of vegetable oil down the drain once the P-traps has been refilled with water.

If your bathroom is smelling as a result of the shower drains, some steps you can use in cleaning the shower drain include:

  • Take the cover off the drain using a screwdriver.
  • Using hot water, disinfect the shower drains.
  • Repeat the process by disinfecting the cover.

2. Black Flakes From Your Jacuzzi Tub

Why Unused Bathroom Smells Like Sewer After Use

Another reason you may find your unused bathroom smelling like a sewer is as a result of having black flakes coming out of your jacuzzi tub sink. Having this biofilm will cause your bathroom to stink like a sewer.

Furthermore, if there is a buildup of mildew or guck in the sink that can cause your bathroom to stink like sewers, to combat this issue, take the following steps below:

  • Using home remedies to take care of this problem, start by pouring into the drain ½ cup of baking soda and ½ cup of distilled white vinegar.
  • Put a lid over the mixture and close it for 30 minutes.
  • After 30 minutes, use a plunger to clear to try and get the clog out by using the plunger to create a seal.
  • Pour warm water into the drain for a couple of minutes
  • If the clog remains, you can still repeat step 1. Even after all that, if the clog remains, then contact a specialist to get it done.

3. Cut Vent Pipe

Another reason why the bathroom would likely still smell may be due to cut vent pipes in the wall or improperly installed vent pipes.

The vent pipe sends odors out of the house, but if it is cut or not fixed properly, the odor will be redirected right back to the bathroom. Get a hold of a professional to get this fixed immediately if that is the case.

4. Loose or Broken Seals

Broken seal could cause a sewer smell in your bathroom

Another reason why your unused bathroom smells like sewer could be a broken seal. If the toilet seat is loose or broken, they will allow sewer gases into the home. The toilet is majorly attached to the drain with seals.

The most likely way is if there is leaking water around the seal, it breeds the growth of bacteria that causes the unpleasant odor.

This is a major issue that you can most likely fix yourself, but if you can’t, you can contact a professional to get it done for you.

5. Clogged Plumbing Vents

Clogged pump vent

If the toilet is giving out a gurgling sound, it might as well be due to the plumbing vent that leads outside being clogged.

The main reason for having the plumbing vent is to release sewer gases outside and provide air backflow back into the plumbing vent.

If the vent is not properly fixed or it’s broken, the sewer gases won’t be released outside, and this, in turn, will make your toilet water gurgle. This could be why your Unused Bathroom Smells Like Sewer.


Having a sewer smell in your bathroom can be very harmful. It would be wise to start investigating the source of the problem as soon as possible.

Listed above are some things that may likely be the cause of the sewer smell, but after doing all you can and you are still unable to detect why your unused bathroom smells like a sewer, and you are unable to fix it, just contact a professional to get it figured out and also aid in fixing the problem.

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