Why does my unused shower smell like sewer?

Author: Earline Bergnaum  |  Last update: Saturday, November 22, 2025

It is not unusual for an unused bathroom drain to start smelling after a period of time. The smell coming from an unused tub or drain is usually coming from the P-trap. A P-trap is the U-shaped portion of pipe underneath the drain. The trap is supposed to keep sewer odors from coming into your bathroom and home.

Why is there a bad smell coming from my unused shower?

If your shower isn't used often, the water in the P-trap can evaporate, allowing odors to seep into the air. Running water through the drain periodically can keep the P-trap filled and prevent this problem.

How to stop an unused shower drain from smelling?

A concoction of white vinegar, baking soda, and hot water will help to eliminate odours from smelly shower drains effectively, as well as removing a buildup of grease, bacteria, and any other biological material residue (as long as the blockage is not severe).

Why does my new shower smell like sewer?

If your shower drain smells like a sewer, then this is a sign that your P-trap may not be doing its job of blocking sewer gases from escaping into your bathroom. If you're dealing with a mustier or general odor, then your P-trap could still be the problem, but in this case, it likely needs to be cleaned.

Is it bad to leave a shower unused?

Risks of leaving a shower unused over time

If a shower is not used over a long period of time, this results in the formation of germs that can be harmful to health. Water stagnating in the pipes provides the ideal breeding ground for different kinds of bacteria.

Shower Drain Smells Like a Sewer? Quick Easy Fix

How long should you run a shower that hasn't been used?

When you first move into your home, run the bath and hand basin taps continuously for at least five minutes. This will flush through any bacteria. If your shower has not been used for a week or more, run water from both hot and cold supplies through the shower hose and showerhead for two minutes.

Do pipes burst if not used?

Pipes typically burst when exposed to extremely low temperatures for an extended period of time (anywhere from 1-3 days depending on temperature). This is especially true for pipes located on exterior walls. A frozen pipe is likely to burst when any water or liquid trapped within it freezes and begins to expand.

Is it safe to shower in water that smells like sewage?

This can happen if your hot water heater temperature is too low or if it's turned off for long periods of time, like when you go on vacation. Fortunately, the bacteria in the hot water heater should not be harmful to you, but it will need to be eliminated in order to remove the smell from your tap water.

How to tell where sewer smell is coming from?

Where is the odor coming from? Check your home's drains, toilets, and plumbing fixtures for any signs of leaks or damage. Look for cracks, loose connections, or broken seals allowing sewer gas to escape. Additionally, inspect your sewer vents on the roof or outside your home for any obstruction or damage.

How to fix a dry P-trap in shower?

If dry, the p-trap cannot perform its function correctly. To eliminate odors coming from a dry p-trap, pour half a gallon of water into the trap to restore the barrier. It will prevent the odors from seeping through the drain.

How often should I run water in an unused bathroom?

Here are some things to do if you have a bathroom that does not get used that often: The main thing is to run water in the sink, shower and flush the toilet at least once a week.

Do drains smell if not used?

Bacterial growth: Inside your drain, there are bacteria that feed on organic matter. Static water can build up in the P-trap, the U-shaped pipe beneath the drain, when the bathroom fixture doesn't run for a while. This stagnant water turns into a haven for germs, which give out foul smells.

How do you deodorize a shower drain?

First, pour one cup of baking soda followed by one cup of white vinegar down the drain. Cover the drain and allow the mixture to fizzle inside of the pipes for a few minutes. Once the fizzle starts to subside, rinse the drain with hot water.

How to stop sewer smell in bathroom?

How to Rid Your Bathroom of Sewer Smell
  1. Check Your Toilet. A common culprit of sewage odor in the bathroom can come from the toilet. ...
  2. Clean Your Sink Overflow. The small hole in your sink has a purpose. ...
  3. Clear the Drains. ...
  4. Use Your Appliances and Fixtures.

How to clean a P-trap in a shower?

How To Clean Shower Waste Trap?
  1. Use a screwdriver to take off the drain cover.
  2. Wear gloves and use pliers to extract any hair or gunk you can reach.
  3. Pour a pot of boiling water down the drain to break up soap and grease.
  4. Mix 1/2 cup of each, pour it down, and let it sit for 15 minutes. ...
  5. Use a plunger for stubborn clogs.

What does a shower P-trap look like?

P-traps, named after their shape, contain a u-shaped bend that filters wastewater as it enters a plumbing system. The trap is connected to a sink, bathtub, and shower with a J-bend on one end and exits into your drainage system. The J-bend is the section of the p-trap that resembles the letter J.

Why does my bathroom smell like sewer but no leak?

A sewer gas smell in the bathroom can be caused by:

evaporation of water in the P-trap piping. broken seal around the toilet in the wax ring or the caulk. A burst pipe. tree's roots have grown into or have caused damage to your sewer pipes.

Can sewer smell come and go?

Due to the frequent movement of water and waste through your plumbing system, and the varying use of different drains throughout the day, some issues can fluctuate. This means that you may only notice the symptoms of a problem, like a sewage smell, at certain times of the day or in response to certain action.

Is it safe to stay in a house that smells like sewer?

Answer: Only under extremely unusual circumstances. Although hydrogen sulfide is a toxic gas, it will not harm people at the concentrations that exist in a house with sewer gas odor problems. Studies have shown that hydrogen sulfide has a depressant effect on the central nervous system in concentrations above 150 ppm.

Why does my shower drain smell but not blocked?

If your shower drain smells musty, you may have mould growing underneath your drain cover. Feel the drain cover to see if it's loose. If your drain cover isn't perfectly sealed, that small wet space will be the perfect breeding ground for mould.

How to remove hydrogen sulfide from water?

Very small amounts of hydrogen sulfide can be removed from water with activated carbon filters (Fig. 1). Activated carbon is used as a granular form in tank-type filters and as finely divided powder in a cartridge. The hydrogen sulfide is adsorbed onto the surface of the carbon particles.

Why does my shower water smell rotten?

Hydrogen sulfide gas (H2S) can give water a “rotten egg” taste or odor. This gas can occur in wells anywhere and be: Naturally occurring - a result of decay and chemical reactions with soil and rocks. Produced by certain “sulfur bacteria” in the groundwater, well, or plumbing system.

What happens if a shower is not used for a long time?

Legionella bacteria can build up in any shower, tap, or water outlet that is not used regularly as the water in the system remains stagnant. When turned on, bacteria will flow out of the system with water, and whoever is using the shower will breathe in aerosols containing Legionella bacteria.

Is it better to drip faucets or shut off water?

Overall, it's best that you take heed and drip your faucets when temperatures dip below freezing. A simple trickle of hot and/or cold water—both from faucets inside and outside the home—can prevent you from having to deal with a much larger issue (and bill!) in the long run.

What happens to unused pipes?

Constant expansion and contraction will put pressure on your unused plumbing, creating weaknesses. One false move – or one incredibly frosty night – and BAM! There goes the pipe. To prevent water from severely freezing you want to keep it running.

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