Why Do I Have Septic Tank Smells In Bathroom?

No one likes having septic tank smells in bathroom. Not only are they unpleasant, but they are usually an indicator that something is wrong.

Having a septic tank smell in house can indicate that you have backed-up plumbing, or at least that is what most people think. However, it can be broader than that. Sometimes, the smells can come from the septic tank itself, which might demand immediate action.

If you have septic tank smells in bathroom and don’t know what to do, you’re in the right place. We’ll give you some common causes of this problem, as well as a few pieces of advice on how to deal with this.

Are Septic Tank Smells In Bathroom Dangerous?


The first thing that is likely worrying you is whether septic tank smells in bathroom are dangerous. Unfortunately, the answer is ‘yes’. Having a septic smell in bathroom isn’t a good thing for more than one reason.

Since the main gas in a septic tank and sewage is methane, it can be hazardous for your health. Most notably, this gas is flammable, so it can be a danger for your entire household. [1]

At the same time, high amounts of methane can affect your health. Some of the symptoms of methane poisoning include:

  • Headaches
  • Nausea
  • Weakness
  • Dizziness
  • Vomiting
  • Loss of coordination
  • Loss of consciousness
  • Suffocation

Also, septic tank smells in bathroom may be an indication of various kinds of sewage problems. Some are more dangerous than others. For example, having a clogged P-trap that you need to replace isn’t an urgent matter, but challenging sewer issues are.

What’s Causing the Smell?


Unfortunately, there isn’t one single reason behind septic tank smells in bathroom. While you may be tempted to use septic tank odor neutralizer, these won’t eliminate the cause of the issues. They’ll only mask a problem. Sure, this is okay if you’re having guests over, but it would be smart to wait and try to find the source of the smell.

To try to determine what’s causing the bad smells, you should check:

  • Shower drain – If you’re having a septic tank smell after showering, maybe the cause isn’t the tank itself, but the product build-up.
  • The toilet – If the smells are coming from your toilet, maybe you have a broken seal or an improper vent pipe.
  • The sink – Similarly to the shower drain, bad odors coming from the sink might indicate that you have a buildup.
  • Washing machine – This can mean a lot of things, and some of the problems connected with it are a dry P-trap or various pipe clogs.
  • Water – If the water itself is smelling, you might have bacteria or other potentially harmful minerals in your water.

We’ll explain in greater detail how these issues occur, and what you can do to fix everything.

Biofilm Accumulation

We use all sorts of products during showering, such as body oils, shampoos, soap, conditioner, shaving creams… All of them wash down the drain together with other debris such as hair and skin cells. As time goes on, these substances can accumulate in the pipes located underneath the shower or the sink. This accumulation is known as a biofilm. [2]

As biofilm accumulates, it releases a sewage odor that smells the same as a septic tank. The bacteria from the biofilm emits a sticky substance that keeps it stuck to the side of the pipes, so they can be quite challenging to remove.

If you want to know how to eliminate septic tank odor that comes from biofilm accumulation, here are a few tips:

  • Remove the shower drain with a screwdriver.
  • Slowly pour the boiling water down the shower drain.
  • Then, pour a cup of white distilled vinegar.
  • Right after, pour half a cup of baking soda.
  • Wait for two hours, then once again pour a gallon of hot water.
  • Finally, use a drain brush to clear out any remaining debris.

Related: Drain Clogged With Hair

Dry P-Trap

Dry P-Traps are another common cause of septic tank smells in bathroom. The P-Trap is that U-shaped pipe you see beneath the sink, but there are also P-traps (or other types of waste traps) underneath bathtubs, showers, and washing machines.

If the septic tank odor is coming from the drain and you haven’t used that shower or sink for a while, chances are the water has simply evaporated and the smells will go away after you turn on the water. However, if the smells are coming from the sink you use regularly, chances are you have some more or less severe problem.

It’s not easy to give you tips on how to get rid of septic smell in bathroom if the P-trap is in question. It all depends on why the pipe is dry. You may begin by removing it to clean it, but if the pipe isn’t clogged, it might be a good idea to contact a professional or to replace a P-trap altogether.

Improper Vent Pipe

An improperly cut or installed vent pipe can be a common cause of a septic tank smell that comes from the toilet. The vent pipe serves as a pressure regulator and it redirects odors.

For example, it can prevent the smell from your septic tank to enter your home.

Sometimes, however, the vent pipe isn’t properly installed, or it’s cracked. Both of these issues can cause septic tank smells to infiltrate your home.

Unfortunately, these two problems can be challenging to deal with on your own, so a good idea would be to contact a professional. They will use a smoke machine that will fill the pipe and that they can trace to see the source of the leak.

Broken Seal

A broken toilet seal can cause many issues, such as water leaking from the toilet base or septic tank smells in the bathroom. If you notice bad odors, as well as your water bowl not filling up properly, or even a leak under bathroom floor, chances are you have a broken seal.

These smells don’t really come from your septic tank, but the standing water leads to the bacteria build-up. To get rid of this terrible odor, here are a few things you can do:

  1. Apply caulk to the seals.
  2. If your toilet bowl is loose, replace the existing toilet ring with a new one.
  3. Replace the broken seals.

Contact a professional plumber if nothing else works.

Overflow Buildup

Many sinks come with an overflow mechanism. This feature prevents overflows to spill into the bathroom. This area is a perfect location for mildew and grime build-up, and these can smell.

Fortunately, it’s very easy to clean the overflow buildup. Here’s what you need to do:

  • Scrub the overflow interior with a small bottle brush.
  • Create a 50/50 solution of water and chlorine bleach. [3]
  • Apply the solution to the overflow area with the same bottle brush and scrub it once again.
  •  Rinse it with warm water.

These four steps should be enough to help you remove the cause of the bad smells.

Drain Clogs


Drain clogs are a common problem in all areas where there are pipes. Yes, they can lead to bad smells, and some might feel just like septic tank odors.

Several things can clog a drain, from organic things like hair to mineral build-ups. No matter what causes the clog, this will lead to bacteria formations, which will create a nasty odor. If you don’t treat it in time, that clog will only increase, and the build-up will become much larger. In return, this will increase the bad smells.

Fortunately, there are a few things you can do to get rid of drain clogs. There are many home remedies for clogged drains you can use if you don’t feel like using harsh chemicals. Also, you can use a drain snake or a bottle brush to clean out most clogs.

Bacteria in Water Heater

If the smell is only present in hot water, chances are you have a faulty water heater. From time to time, bacteria can form in the water heater if the water inside of it isn’t hot enough. These bacteria usually aren’t harmful to humans, but they can produce a bad smell in the bathroom.

Try to increase the temperature of the water heater for up to a day. Hot water can kill bacteria. Run the water through the taps to ensure all the remaining bacteria are killed.

If you suspect more things are polluting your water, you might want to contact the local water testing lab that can examine the water. You don’t want to ingest something poisonous.

Read Next: Muriatic Acid For Toilet Cleaning 

The Bottom Line

Having septic tank smells in bathroom rarely means the problem is in the septic tank itself.

Most of the time, the issue lies in clogged drains or some other plumbing issue.

There are several parts of the plumbing system that prevent odors from entering your home. If any one of them is broken, clogged, or working improperly because of any reason, this might lead to bad smells infiltrating your bathroom.

You should attempt to fix this issue as soon as possible, and not just because of unpleasant smells. Septic tank gasses can become a severe health hazard. Not to mention you’re risking serious plumbing problems.

Read Also: Why Is My Toilet Bubbling