Why Do I Smell Sewer Gas in my Bathroom?

Everyone strives to keep their bathrooms clean and have them smelling fresh. After all, it is one of the most frequently used spaces in any home.

However, it’s not uncommon for your bathroom to start smelling like sewer gas at some point.

If you are interested in identifying and eliminating this problem, this guide is for you.

Why Do I Smell Sewer Gas in my Bathroom?

There are a number of reasons why your bathroom may smell like sewer gas. This includes:

  • Dry or leaky p-pipe in your shower drain
  • Biofilm accumulation in your shower drain
  • Dry or leaky p-pipe in your sink
  • Grim and mildew build-up in your sink’s overflow
  • A loose or compromised toilet leak
  • Badly installed or damaged vent pipe
  • Bacteria in your water heater

If you wish to eliminate the sewer gas smell, you will need to first identify its source.

Sewer Gas vs Other Odors

Before looking at the ways to eliminate sewer gas smell, you should know how to identify it.

It’s not uncommon for bathrooms to develop certain odors from time to time. However, many of these smells go away on their own or after a thorough cleaning.

The smell of sewer gas typically persists until its source is found and fixed. This means it will linger for many weeks or months, and possibly grow more prominent with time.

Identifying Sewer Gas Smell

Sewer gas is composed of many different compounds. This includes:

  • Hydrogen sulfide
  • Ammonia
  • Methane

The compound with the most prominent smell in this mix is hydrogen sulfide.

It gives sewer gas the distinct smell of rotten eggs.

Hydrogen sulfide does not usually occur in bathrooms under normal circumstances. So if you notice it prominently for a long period, you may have a sewer gas problem.

Is Sewer Gas Dangerous?

The issues associated with sewer gas go far beyond just its unpleasant smell.

The gas fumes from hydrogen sulfide are actually both toxic and highly flammable. This flammability has caused explosions in sewers in the past. Therefore, there is a risk of danger if you leave sewer gas problems unaddressed.

Some of the health problems associated with exposure to low concentrations of sewer gas include:

  • Eye irritation
  • Dizziness
  • Nervousness
  • Headache
  • Nausea
  • Drowsiness

Sewer gas tends to be much more dangerous at high concentrations.

Some of the dangers associated with exposure to high concentrations include:

  • Loss of consciousness
  • Asphyxiation
  • Sudden death

As you can see, there are numerous dangers associated with sewer gas. If you suspect you have a sewer gas leak in your bathroom, you should address it immediately.

Causes of Sewer Gas

As mentioned above, there are many different causes for sewer gas.

Some of these are easy to spot, while others may take some extra effort. Let’s look at each of these causes and how to correct the problem.

Sewer Gas Odors from Shower Drains

Many people think that all strange odors in their bathroom originate from their toilet. However, sewer gas can originate from your shower drain as well. In-fact, your shower drain should be one of the first places to check for a sewer gas problem.

Sewer Gas from Dry P-Trap

The P-trap is a U-shaped bend in your sink’s drain pipe. It connects your sink to your home’s septic tank or sewer system.

They are designed to always contain a small amount of water. This water acts as a buffer that keeps gases and odors from sewers from escaping out through your drain.

If you haven’t used your shower for a while, this water may evaporate away. With no water in place, sewer gases are free to enter your bathroom and accumulate.

However, you may be able to fix this problem by simply running your shower. If the problem persists, you may have other P-trap issues.

P-trap problems can still occur if you use your shower regularly. A leaky P-trap won’t be able to hold water, and will allow sewer gases to pass through. This problem can only be fixed by repairing or replacing your P-trap.

Shower Biofilm Accumulation

You may already be aware of the amount of substances that wash down your drain regularly. This includes dead skin cells, shampoos, conditioner, soap residue, etc.

Most of these are carried away by water.

However, a small portion will accumulate in your pipes and p-trap. This accumulation is known as a “biofilm”.

When biofilm builds up over time, it starts to decompose from bacteria. This decomposition produces a sewage smell. You can try scrubbing away these bacteria.

However, they produce a sticky substance that helps them stick to pipes. Therefore, you will need to use specialized products to remove them properly.

A strong drain cleaner can help resolve the issue. You can also make your own natural cleaner at home.

This involves using a combination of hot water, white vinegar, and baking soda.

You can start by pouring very hot, but not boiling, water down your drain. Then add some vinegar to the drain.

Lastly, add half a cup of baking soda. Let this mixture sit for two hours before washing it down with more hot water.

Sewer Gas from the Toilet

The toilet is also where a lot of sewer gas or similar smells originate from.

You may be able to fix such problems with a quick clean or by flushing a few times.

However, this may not always solve the issue. Let’s examine the causes of sewer gas from toilets.

Loose or Compromised Seal

A persistent sewage smell from a toilet may be caused by a loose or compromised seal.

The typical toilet connects to your drain via two separate seals. It’s not uncommon for at least one of these to be loose or broken.

In some cases the seals may be improperly installed. When this occurs, sewer gases may enter your bathroom. You may be able to fix the problem by reinstalling the seal.

In other cases, you will need to fix cracks or broken seals. You can use caulk on the seals for this purpose.

Also apply this caulk to the bolt holes connecting your toilet to the ground.

Badly Installed or Damaged Vent Pipe

You may also notice a sewer smell coming from the walls around your toilet. This may be due to a badly installed or a damaged vent pipe.

This vent pipe keeps your home’s plumbing system pressure normal. They also direct odors away from your home and to the outside.

If your vent pipe wasn’t installed properly or is damaged, they may leak odors. You can correct this problem by getting your pipe installed properly.

A professional plumber can take care of this for you. If the pipe is damaged, a plumber can locate the source of the crack and repair it.

Sewer Gas from the Sink

Sewer gas may also originate from your sink. There are many different ways this happens. For example, your sink also contains a P-trap like your shower does.

If this P-trap is dry or leaky, it will let sewer gases enter your bathroom. 

Sewer gases may also accumulate due to a buildup in your sink’s overflow. This is the hole near the top of your sink that prevents it from overflowing.

This overflow can accumulate grime over time, which can produce a sewer gas-like smell.

The good news is that this problem is easy to fix. You simply need to scrub the inside of your sink overflow with water, bleach, and a scrubbing brush.

If this does not correct the problem, you may need to hire a professional to examine the issue.

Sewer Gas from Your Bathroom Water

In some cases, the sewer gas-like smell may originate from your water.

Let’s look at the two ways this can happen.

Odors When Using Hot Water

You may notice the sewer gas smell only when using hot water. This could be when you’re taking a shower or using the sink.

This may indicate a problem with your water heater.

Bacteria can get into your water heater and expand their colonies inside. You can correct this problem by increasing your heater temperature and leaving it for a day.

The hot temperatures should kill off most or all of the bacteria.

Odors When Using Water of Any Temperature

You may notice sewer gas odor from your water at any temperature. This may indicate high levels of hydrogen sulfide in your water.

It is rare for hydrogen sulfide concentrations in water to reach dangerous levels. However, you should still send a water sample to a lab for testing.

Final Thoughts

As you can see, there are plenty of reasons for sewer gas odors in your bathroom. So be sure to check your shower, sink, and toilet for problems.

It is vital to address this problem quickly, as it may indicate something more serious.

If you can’t get rid of the odor, you should consider calling in a professional. A plumber can perform a thorough assessment and locate the source of the smell.

They can then help correct the issue before it creates bigger problems.

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