A sewage backup occurs when solid waste or wastewater is prevented from passing through drain pipes or sewer lines. Sewage backups are not only unsightly and a pain to deal with, but they also pose a significant danger to health.

In this article, we will discuss the causes of sewage backups, the warning signs, and measures for its treatment and prevention.

What causes sewage to backup?

Common Causes of Sewage Backups

1. Clogging

If the sewage backup is confined to a single source, be it a sink, tub or toilet, then the drainpipe is most likely to be clogged up. But, if the backup is widespread and recurrent, then the issue lies with the sewer line.

Common causes of blockages include flushing solid and insoluble objects down the drain such as wet wipes, diapers, hair, cooking oil or grease, feminine hygiene products, paper napkins etc.

2. Obstruction

A surprisingly common cause of obstruction in sewer pipes is trees. More specifically, their roots.

Tree roots can crawl into sewer lines through cracks and holes, in search of moisture and nutrients. This is more likely to occur in drought-prone regions and during dry seasons as water scarcity can drive trees to look for water in unconventional places.

Once established within the pipeline, the roots continue to grow, eventually blocking off the passage and causing sewage backups.

The roots can even wrap around the sewer line and destroy it. Sewer lines made out of cast iron or vitrified clay are more susceptible to root invasion because of their brittle and porous nature.

3. Damaged Sewer Lines

The age and condition of sewer lines are a good way to gauge the probability of sewage backups.

Old and worn-out sewer lines tend to develop cracks over time, which then allow impurities to enter the pipes; impurities such as rocks and dirt, the build-up of which can clog the lines and lead to backups.

4. Breakdown of Sewer Lines

Wear and tear due to passage of time, lack of proper care and maintenance, structural defects, and acts of god can cause a complete break-down or collapse of sewer lines.

When this occurs, some of the wastewater is discharged into the earth. But the majority remains stuck inside the lines, resulting in sewage backups.

5. Linking Unrelated Pipelines

Linking sump pumps, gutters, downpipes etc. to sewer lines can lead to an increased risk of backups.

Since they are designed to handle relatively small volumes of wastewater, tasking sewer lines with stormwater drainage can overpower their drainage capacity.

6. Flooding

Heavy storms can result in large amounts of rainwater or runoffs from melting snow to enter the public sewer lines.

If they are unable to handle the sudden influx, the excess water can enter sewer lines in residential and commercial areas through inter-connected pipes and lead to backups.

7. Blockages and Breakdown

Blockages can also occur in the main sewer lines. Undetected or untreated blockages can end up affecting sewer lines at homes and offices. Similarly, negligent or improper upkeep can cause municipal sewer lines to deteriorate and collapse.

8. Vandalism

It is not uncommon for municipal sewer lines to be set upon by miscreants. Vandals have been known to rip off or break sewer pipes, cause blockages by using rocks, dirt, sticks, etc.

Vandalism can be hard to detect, particularly when the sewer lines are located in remote and unfrequented areas.

Health Hazards from Sewage Backups

Sewage backups can trigger a whole host of health issues. The pathogens present in the backups can result in:

  • Gastrointestinal issues such as vomiting, cramping, and diarrhoea
  • Liver diseases such as hepatitis and jaundice
  • Respiratory problems such as asthma and inflammation of lungs
  • Skin, eye, throat, and nose infections, and
  • Death in severe instances.

The pathogens can enter the human body through direct physical contact with a contaminated surface, or indirectly, through inhalation of contaminated air or absorption through the skin.

Warnings Signs of Imminent Sewage Backups

The following signs are indicative of damaged drain pipes or sewer lines, necessitating prompt redress:

  1. Foul Odour: Drains emitting foul odour or the presence of sewage smell in the house or building are strong indicators of sewer lines that are experiencing problems while transporting waste.
  2. Clogging in Multiple Drains: When more than one drain is clogged up, it means that the functioning of the sewer line has been affected. If the clogging occurs in rarely used drains such as the ones in spare bathrooms, it can point to an extensive backup in the sewer lines.
  3. Slow Drainage: Slow flushing toilets or slow draining sinks are also a sign that pipes or sewer lines are clogged up. The issue is more serious if slow drainage is noticed on the higher levels of the house or building.
  4. Bubbling and Gurgling: Clogged pipes can trap air molecules which then cause bubbling and gurgling whenever toilets are flushed or sinks are drained.
  5. Plumbing Problems: If, when using one plumbing fixture, it results in sewage backups in fixtures, not in use, it is a clear warning sign. For example, if flushing the toilet causes the shower to backup.
  6. Issues with Cleanout Pipes: Another sign is wastewater coming out of cleanout pipes or the build-up of wastewater in such pipes before it finally gets pushed out. Sewage water may also accumulate in the basement or the lawn.
  7. Infestations: Rodent, cockroach or fly infestations can be an indication of damaged or broken sewer lines. These disease vectors can get into the drain pipes through cracks, and make their way into homes and office buildings.
  8. Mould Growth: Mould requires a warm and humid environment to grow. Mouldy walls can be a sign that sewer pipes running behind the walls have sustained damage.
  9. Cracks in Foundation: A broken sewer line can cause cracks in the foundation. If left untreated for too long, it can result in sinkholes.
  10. Lawn Appearance: Broken sewer pipes can drench the soil and cause a depression in the lawn. Another tell-tale sign is a patchy lawn, i.e. the grass is greener in certain areas than in others.

Mitigating Measures and Treatment Plan in the Event of a Sewage Backup

Evacuate: Get any children, pets, the elderly and the vulnerable to move to a safe location, and keep them away from the spillage.

Shut-off Power: Provided it is safe to do so, cut-off power supply to areas that have been affected.

Stop using the Plumbing: You can compound the problem by continuing to use the plumbing system. Do not attempt to drain sinks or tubs, or flush toilets. Turn off the running water supply.

Protective Wear: Access the affected area and handle contaminated objects after donning protective gear such as glasses, rubber boots, gloves, mask etc. Do not let anything in the affected area come in contact with exposed parts of your body.

Ventilation: Let the noxious fumes dissipate, and fresh air circulate by opening doors, windows and curtains. Sunlight, a natural disinfectant, can help stem the growth of harmful bacteria and mould.

Discard Contaminated Objects: All contaminated objects such as upholstery, carpets, curtains etc. should be appropriately disposed of. Items that can be salvaged should be professionally cleaned.

Isolate Uncontaminated Objects: Remove all uncontaminated objects situated in the proximity of the spillage, and store them in a safe space.

Disinfect the Affected Area: Disinfect standing water with chlorine bleach.

Get Professional Help: Promptly and without delay, seek the assistance of professionals who provide sewage clean-up and restoration services. After the backup problem has been fixed, engage the services of professional cleaners, particularly if the damage is widespread. In lieu of it, clean the affected area thoroughly, including walls, floors, furniture and fixtures etc. Inspect for and take suitable measures to eradicate mould.

Inform Relevant Authorities: Inform the municipal authorities and insurance companies of the sewage backup as soon as possible. Also, visit your doctor for a health evaluation.

Preventing Sewage Backups from Reoccurring

Some dos and don’ts to prevent sewage backups:


  • Modernise your existing sewer lines by replacing it with plastic piping. Plastic piping will last longer and can also help keep out tree roots.
  • Flush only toilet paper down the toilet.
  • Waterproof the basement.
  • Seal cracks, if any, in the foundation.
  • Plug drains, especially if your area is prone to flooding and rainstorms. Backflow or backwater valves are great for stopping sewage backups.
  • Maintain the sewer line that runs between your home or building, and the city’s mainline.
  • Regularise cleaning and inspection of drain pipes.


  • Flush oil or grease down the drain. They can harden inside the drain or sewer line, and create blockages.
  • Discard hair, food waste, sanitary napkins, or other such objects in the toilet.
  • Use harsh chemicals to self-treat clogged drains. They can damage the drain pipes.
  • Plant trees in the vicinity of the sewer lines. Once trees take root in the pipes, they would most likely have to be replaced.
  • Ignore the warning signs of sewage backups.

Sewage backups can cause a lot of anxiety and panic. Regular maintenance, periodic inspection, and being prepared for emergencies can help avoid costly mistakes and make the process of dealing with sewage backups easier and stress-free.

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