How it works

You can learn how the plumbing in your building works with the sewer system.

Plumbing systems

The plumbing in your building contains pipes, vents and traps. Each fixture (toilet, sink, shower or floor drain) drains to the pipes that carry the wastewater from your house to the sewer pipe.

Vents in these fixtures allow odors and gases to escape, as well as allowing pressure to enter, preventing backpressure when water fills the pipes. The trap in each fixture, when properly vented, provides a liquid seal that prevents gases from entering the building. If a fixture is not used regularly, the water in the trap may evaporate, causing the loss of the trap seal and allow gases to enter the building. Pouring water down the drain will restore the trap seal. Remember that sewer gases can be fatal.

An accessible cleanout is required near an outside wall where the building drain connects with the sewer. This cleanout is used when the lateral from the building to the sewer needs to be cleared of obstructions. You can avoid these obstructions by preventing grease, hair, washing machine lint and disposable diapers from entering the lateral in the first place. Cleaning the sanitary service is the responsibility of the building owner.

Sewer backups

If you experience a sewer backup, you can contact Sewer Maintenance to find out if the problem was caused by a public sewer. There is no fee to request a check a public sewer. If the problem is not in the public sewer, you may need to call a professional contractor to assess the issue. Backwater valves may reduce the likelihood of sewer backups.

Contact sewer maintenance

Minneapolis sewer system

Sanitary sewers typically run down the middle of a street. Sewer manholes are built on top of the sewer pipe, allowing access for maintenance crews. These smaller sewer pipes discharge into larger pipes, before the wastewater empties into large tunnels, eventually going to the Metropolitan Wastewater Treatment Plant in St. Paul.

Sewers usually flow downhill, using gravity to move the wastewater. When gravity doesn't work, pump stations force wastewater to a higher elevation, where gravity takes over again.

Here is what happens when the wastewater reaches the treatment plant:

  • Wastewater passes through a large iron grate to separate large items
  • Solids are then settled out, collected and incinerated
  • Bacteria is used to remove organic materials and nutrients, before the bacteria is settled out
  • Phosphorus and nitrogen are removed, and chlorine is added
  • The water is finally ready to be released to the Mississippi River

Stormwater runoff

Stormwater runoff enters storm drains in the street, before flowing through storm pipes and then discharges into the Mississippi River. The storm drains are important to controlling runoff. They should be kept free of debris and nothing but stormwater should go into them. Some storm drains in Minneapolis have messages like "Flows to lake - keep drain clean" on them.

See storm drain stenciling for more information about the program

Stormwater runoff flows off hard surfaces such as

  • Roofs
  • Driveways
  • Parking lots

It collects pollutants such as

  • Vehicle oil and grease
  • Construction site sediment
  • Bacteria from animal waste
  • Excess lawn fertilizer and pesticides
  • Airborne pollutants, such as nitrogen, mercury, other metals, combustion emissions and pesticides

A typical downtown block produces about nine times more runoff than a wooded area of the same size! Rainwater washes the hard surfaces, and the first runoff carries these pollutants directly to bodies of water through the storm drain system. To keep these pollutants from reaching our waters, the City builds holding ponds and grit chambers that allow the pollutants to settle out, as well as establishing wetlands to filter out pollutants.

Contact us

Surface Water & Sewers

Public Works




Public Service Center
250 South 4th St, Room 300
Minneapolis, MN 55415

Office hours

Monday – Friday
7 a.m. – 3:30 p.m.