Why does the smell of sewage appear in the bathroom and how it can be eliminated

Nikolay Fedorenko
Checked by a specialist: Nikolay Fedorenko
Author: Irina Yakushchenko
Last update: March 2020

Smells play an important role in our lives. Even the impression that a house makes on a person is called its atmosphere. Mistresses do their best to make it pleasant: they clean, take care of ventilation, use air fresheners.

If there is a smell of sewage in the bathroom, it quickly spreads throughout the house and literally poisons life. Let’s figure out how to deal with it.

Sewer stink is dangerous

It is impossible to get used to the sewer smell. Volatile gases from the siphon and pipes are distributed throughout the premises of the house or apartment. This stink is disgusting, spoils the mood. When guests arrive, the owners of the "fragrant" home have to apologize and make excuses.

Psychological discomfort is far from the worst that a sewer stink carries with it. Much worse is that it is dangerous to health. The ability to separate odors into pleasant and unpleasant is a biological mechanism that has ensured the survival of mankind for millennia. If the fragrance seems unpleasant, it means that it is potentially dangerous.

Air from the sewage system is “aromatized” with ammonia and hydrogen sulfide. It also includes methane, which has no pronounced odor. Volatile gases affect the state of the human nervous system. A sensation of causeless anxiety, nervousness, irritability may appear.

Fighting sewer stink
The harm that a sewer stink can cause to a person depends on the composition of the air and the concentration of toxic gases. In any case, the smell should be disposed of immediately as soon as it appears.

In a house that smells of sewage, people can mourn, break down, have trouble sleeping and even faint. Long-term exposure to hydrogen sulfide can lead to respiratory diseases: rhinitis, bronchitis.

With a high concentration of gas in the air, poisoning is not ruled out, the symptoms of which are nausea, vomiting, headache, decreased pressure and dizziness.

Ammonia negatively affects vision, respiratory system, causes a state of excitement, has a general toxic effect. And methane can cause oxygen starvation of cells. Some disturbances in the functioning of the autonomic nervous system are not ruled out. For example, a “twitching eye" may well indicate a prolonged exposure to methane on the body.

At the first sign of a sewer smell in the bathroom or toilet, you should immediately look for the cause of the stench and eliminate it. Otherwise, the concentration of gases in the air will only increase, and this can lead to negative consequences for the health of the residents of the house.

The reasons for the smell in the bathroom

To better understand how the air from the sewer enters the room, you need to have at least a general idea of drainage system. It consists of a riser into which drains from all apartments or plumbing fixtures in the house merge, pipes, plumbing fixtures with siphons.

It is a siphon formed by a water trap that should prevent air from entering the bathroom from the sewer. Water is constantly in the bends of the device. If water is out water seal partially or completely disappears, this causes a smell.

Scheme of the sewerage device in the house
Sewerage schemes can vary significantly depending on the type of housing, the number of plumbing fixtures, but the general principles of the device are always the same

Wastewater flows into the riser by gravity due to the difference in levels at which the sewer pipes are located. For normal operation of the riser, air must flow in from above, so its upper part extends into the fan pipe, which provides ventilation.

If fan pipe incorrectly mounted or clogged, the air begins to flow into the sewer through weak seams and joints of the pipeline or through siphons. In the second case, the water seal partially or completely disappears, because it is sucked into the sewer system.

The lower the siphon, the more likely it is to happen, and the lowest level of siphon placement is at the bathtub.

Siphon device for bath
The volume of the water lock in the siphon of the bath can be different, and the degree of protection against stench in the room depends on it. When buying a device, you should give preference to a device with a deep water trap with a volume of 300-400 ml or more

There are several main reasons why an unpleasant odor appears in the bathroom:

  1. Errors in the design or installation of sewers. If the system is not assembled correctly, a constant stink is guaranteed. Air fresheners and household chemicals will not solve the problem. Have to spend money: you need to redo the system, and this should be done by qualified craftsmen.
  2. Incorrect sewer pipe angle. If the angle is too small, sewage stagnates in the system and the smell of decay appears.A fundamental solution to the problem is also expensive: you need to rebuild the pipeline. You can do with half measures - change the gaskets and carefully seal the joints.
  3. Siphon malfunctions. If the pressure in the sewage system is above atmospheric, air in the form of bubbles can escape through a siphon into the room. The reason is the filling of pipes with drains. This is possible due to insufficient diameter of the pipes (errors in the calculations during the design of the system), blockages or icing.
  4. Leaks. Water from the sewage system can seep through leaking pipe joints. If the leak is large, it is easy to detect through puddles on the floor. If it’s small, it’s more difficult, because water evaporates quickly and does not drip, but it stinks and contributes to dampness in the room.
  5. Poor ventilation. So that the air does not stagnate, a ventilation system is mounted. It can be natural or forced. If the system was originally improperly installed or the ventilation shaft is clogged, the room will have a musty smell, dampness and fungus.
  6. Pipe clogging. The most common reason for the smell of sewage in the bathroom is clogging. Particles of dirt, debris, sand, hair constantly get into the sewer. Straying into lumps, threads and hair narrow the inner diameter of the pipe, trap dirt from drains. The result is a fetid plug.

If the problem arose due to errors in the installation of sewage or ventilation, its solution should be entrusted to professionals. But with blockages, malfunctions in the operation of devices or leaks, you can figure it out on your own. The main thing is to correctly establish the cause of the stink.

Easy clogging
Sewer blockages can be of various origins. Some types of plugs can be easily removed using household chemicals or improvised means, but sometimes special equipment is required.

In many cases, an unpleasant odor in the bathroom can be easily prevented and timely fight blockages. Against blockages, it is enough to install special nets for draining the bathtub and sink, and regularly clean them of impurities. The grill traps hair and large particles that can clog the pipe.

A common reason for the appearance of a negative smell of sewage are errors made during bath siphon installation. We recommend that you familiarize yourself with the features and rules of this work; you can find them in our article.

How to get rid of unpleasant odors?

First you need to establish what caused the problem. It is necessary to consistently check the operation of the ventilation and sewer system, pipe joints.

To make sure that the ventilation is normal, put a sheet of paper on the grill. If it sticks, everything works fine. There is another simple diagnostic method: a lit match or lighter is brought to the air vent. The flame should deviate towards the shaft. If this does not happen, you need to do ventilation.

Checking ventilation draft
If the bathroom has poor natural ventilation, it is necessary to organize forced. Otherwise, in addition to the musty smell, a fungus will also appear, which can harm the health of people and spoil the decoration of the room

The next step is to check the operation of the sink and bath. You need to open the taps at full power and see how fast the water goes into the drain holes. If slower than usual, this is a sign of blockage.

If the water drains normally, but the smell does not subside, it makes sense to rinse the plums with boiling water. This is more of a preventive measure, but it helps to clean and disinfect pipe walls, and destroy bacteria.

Pipe walls before and after cleaning
Detergent residues, grease, and dirt linger on the walls of sewer pipes and form a dense layer of deposits. These are predominantly organic substances. They decompose and emit an unpleasant odor.

If everything is in order with ventilation and pipes, inspect and feel all the joints of the elements of the sewer system. Nowhere should there be cracks and chips. If moisture is found, attach a dry, white cloth. A wet spot on it will help determine where exactly the water is leaking. This place will need to be sealed.

Option # 1: improve ventilation draft

Natural hoods may become less efficient for several reasons:

  • clogged ventilation shafts;
  • replacing bathroom doors with denser ones;
  • powerful forced air flow from neighbors (relevant for apartment buildings).

It should be noted that in summer, in the heat of ventilation, ventilation is often worse than in winter, for natural reasons. Hot outside air prevents the flow of cold air from cool rooms, and an air congestion forms. This is easy to fix if you leave the bathroom door slightly ajar in the summer.

The scheme of ventilation of a bathroom in a private house
An extractor fan in the bathroom will never be redundant. However, if there is a chance to restore natural cravings, it is better to do so.

Remove the ventilation grill, take a flashlight and inspect the ventilation shaft as far as it is available. Sometimes the blockage is located very close to the exhaust outlet and can be reached with your hands, a hook or a small scoop. It can be a piece of brick falling off the wall of the mine, a dead animal that climbed into the ventilation, or just rubbish.

If the problem is due to a tight door or a high threshold, you can provide additional airflow from under the door leaf. The lower part of the canvas is cut so that the door does not fit snugly on the box and there is a slight gap. A more “gentle” option is to install a decorative grille on the bottom of the door.

Right bathroom door
Special grilles or beautifully designed openings in the bathroom door will ensure normal airflow from other rooms and will help to improve the natural exhaust

If you do not want to experiment with doors, you can simply not close them, but cover them, leaving a small gap for air access. A great option is to install a fan in the exhaust vent. To prevent air from the shaft from entering the room, either an axial fan or a channel model with a check valve is installed.

To stimulate the outflow of dirty air in bathroom exhaust vent it is better to install an axial fan:

Option # 2: cleaning pipes and siphons

There are many useful devices with which you can independently clean the sewer. The most popular are plunger and cable. The first tool is perfect for cleaning the siphon, but it is unlikely to help if the blockage is large and located far from the drain. The second is universal.

The plunger is positioned so that it completely covers the drain hole of the bathtub or sink. After that, open the water until it covers the lower part of the elastic cap, and make several translational movements up and down. Then the plunger is raised and watch the flow of water. If it does not go well, the operation is repeated.

Plunger from the smell of sewage in the bathroom
The plunger is one of the simplest tools for cleaning the sewer. It perfectly replaces chemicals and cannot damage the siphon or pipes. This device should be in every home.

Metal cable - “heavy artillery” for pipe cleaning. If plumbing is plastic, it is undesirable to use it. If the pipes are metal and there is no risk of damaging the siphon, this is a reliable tool.

Rules and Features cable cleaning described in detail in our recommended article.

The cable is passed into the drain hole and slowly rotated, gently pushing further through the pipes. When the tool reaches a blockage, debris will catch on a hook, it can be removed. After that, the sewage system is washed with hot water to eliminate cork residues and dirt.

The metal cable will be in excellent condition and will last for decades, if properly looked after. After use, the cable is washed, wiped dry, lubricated with machine oil, folded and stored in a dry place.

The smell of sewage can be eliminated using improvised means. To do this, you can use soda and vinegar or citric acid. These substances destroy small blockages, remove deposits from the walls of pipes and disinfect them well.

Here are some examples of how to use them effectively:

  • Soda. Pour half a pack of soda into the drain of the bath or sink, leave for 20 minutes. After that, the sewer is washed with plenty of hot water.
  • Vinegar Soda. Soda is poured into the sewer, and then filled with a glass of vinegar, the drain is closed with a cork and washed after 20 minutes.
  • Lemon acid. In combination with boiling water, citric acid cleans pipes no worse than soda with vinegar. Rinse the sewer when the acid stops sizzling and foaming.

Instead of homemade products, you can use ready-made chemicals for pipe cleaning. They are more effective, but unsafe for health, so when applying, you need to wear gloves, protect your skin, eyes, respiratory organs.

Household chemicals for pipe cleaning
When buying, you should carefully read the information on the packaging: for which pipes and types of blockages the product is intended and how to use it correctly

In the list of the best means for cleaning the sewage “Mole”, “Flup”, “Tiret”, “Pothan”, “Mr. Muscle”. They can be sold in the form of liquids, gels, granules. The most powerful are granular products.

If used incorrectly, they can damage plastic pipes, so do not leave compounds in the sewer for longer than the manufacturer recommends.

Valuable recommendations and detailed instructions for cleaning sewer pipes can be found. in this article.

Option # 3: sealing sewer joints

The easiest way to seal the joints with fum, but a more reliable way - processing with special sealant. The ranking of the most popular formulations is led by products of famous brands Ceresit and Tytan. Experts speak well of "Moment", Ciki Fix.

Plumbing sealing compounds are of several types:

  • Silicone. These are expensive sealants, but they differ in good adhesion, elasticity. The compositions retain their properties at high and low temperatures, do not shrink.
  • Acrylic. The main advantage of acrylic sealants is a long service life, good water repellent properties and resistance to temperature extremes. Minus - low elasticity.
  • Silicone acrylic. The best choice. Sealants can be used to seal joints, repair small cracks and chips, and glue surfaces.
  • Polyurethane. On top of the polyurethane compounds can be applied paint. This is a good option if the leak is visible and must be masked. The disadvantage is a strong toxic smell, which disappears after the sealant hardens.

Before starting work, the surfaces should be thoroughly cleaned, drained and degreased. The sealant is applied to the seam in a circle. The line must be continuous. For ease of application and alignment, you can use a soft spatula.

Leakage locations
When buying a sealant, it is better to choose the one that has the mark "sanitary" on it. Fungicides, disinfectants that prevent the appearance of fungus, are added to such formulations.

When the work is finished, the composition is left to dry completely (the time should be indicated on the package), after which you can use the sewer.

Conclusions and useful video on the topic

There are many ways to get rid of bad smell. We offer several useful videos that will help to cope with the sewer stench and prevent its occurrence again.

Video # 1. Useful tips for dealing with leaks in the bathroom:

Video # 2. Brief on the use of soda and vinegar to clean the bath:

You can and should fight the smell of sewage in the bathroom, but it’s even easier to prevent it from appearing. Install the nets on the drain holes of the sink, bathtub, shower.

Prevention will not hurt: once every 1-2 months, flush the sewer with soda or household chemicals. Every six months, check the ventilation and the joints of the sewer system. This is enough to keep the air always fresh and clean.

Tell us about how you struggled with a negative sewer odor. Please write comments in the block below. Ask questions and post thematic photos here.

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Visitors Comments
  1. It is clear that it is necessary to clean and seal the sewer itself. But as for the ventilation in our apartment buildings, I can say that, as a rule, they generally do not meet the requirements. The fact is that mostly from them blows, but the elongation should occur. Accordingly, the ventilation itself either should not be worn at all, or it is necessary to install grilles with exhaust fans.

    • Expert
      Nikolay Fedorenko

      Oleg, you have the right to apply to the Criminal Code to check your ventilation and if they respond, they will not find any violations, and an independent examination will detect them, file a complaint with the Rospotrebnadzor, a court or a housing inspectorate for improper performance of obligations to ensure high-quality ventilation of the MKD premises.

  2. Maria

    Yes, it blows from the ventilation duct, so even forced ventilation (with a fan) does not help. Periodically, life is poisoned by the smell of sewage from ventilation.

  3. We have just such a problem in the house. The stench is simply utterly worthless! They searched for the cause for a long time, washed pipes and stuff. There were no blockages. But it still smells! Mom decided that it was carrying from the shower and began to plug the drain with a stopper. But this is not a solution to the problem! As a result, we reached the drain hole and threw a lot of antiseptics there. The smell has become much less! And her husband now monitors the level of sewage. If it is very full, it is necessary to pump out.

    • Expert
      Nikolay Fedorenko

      Hello. To eliminate odors from the sewer of a private house, a rather complicated device called an air valve is used. True, its installation can be troublesome. On self-contained septic tanks, it is also recommended to install non-return valves in order to avoid drain outflow in the room during septic tank overflow.

  4. Vladimir

    Hello! If the drain hole began to fill up, you need to make a second - overflow.

  5. Olesya

    Thanks for the informative article!

    Great, if you still tell me the option of action in a rented apartment. In the bathroom, the shower drain is mounted on the tiled floor. If you do not use a shower for a couple of days (alternating with a bath), it starts to stink. Flushing special means does not help. With ventilation, everything is ok. Disassembling tiles is not an option. I would not want to move out - otherwise everything suits and the market of 4-room apartments in the right area is very small.