How It Works
The plumbing in your building contains pipes, vents and traps. Each plumbing fixture (toilet, sink, shower or floor drain) drains to the pipes that carry the wastewater from your sanitary service (or lateral) to the public sewer pipe.
These fixtures have vents to allows 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. This can cause 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 (usually located near the vent stack) is used when the lateral from the building to the sewer needs to be cleared of obstructions such as tree roots. You can avoid these obstructions by preventing grease, hair, washing machine lint and disposable diapers from entering the lateral in the first place. The cost for cleaning the sanitary service is the responsibility of the building owner.
If you experience a sewer backup, contact Sewer Maintenance to make sure the problem was not caused by a public sewer. There is no fee to request a check a public sewer. If we determine the problem is not in the public sewer, you should call a professional contractor to assess the issue. Backwater valves may reduce the likelihood of sewer backups.
Minneapolis Sewer System
Sanitary sewers typically run down the middle of a street. Sewer manholes are built on top of the sewer pipe, rising up to street level, allowing access for maintenance crews. These sewer pipes discharge into larger pipes, until the wastewater empties into large tunnels, before going to the Metropolitan Wastewater Treatment Plant in St. Paul.
Sewers usually flow downhill, using gravity to move the wastewater. Sewer pipes often follow streams, which also flow downhill. The main tunnel from Minneapolis to the Metropolitan Wastewater Treatment Plant follows the Mississippi River. When gravity doesn't work, pump stations force wastewater to a higher elevation, where gravity can take 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 flows into grated covers on top of storm drain inlets in the street. This stormwater flows through storm pipes before discharging into the Mississippi River. The storm drain inlets 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 DO NOT DUMP - DRAINS TO RIVER on them. See Storm Drain Stenciling for more information about the program.
Property owners are encouraged to drain stormwater from their property to lawns, gardens or small ponds. Rain gardens can capture stormwater, allowing native plants and soil to filter out pollutants & contaminants from the stormwater. Rain barrels can also be used to capture stormwater from roofs. This water can then be used to water lawns and flower gardens.
Stormwater runoff flows off hard surfaces such as roofs, driveways, parking lots, collecting pollutants along the way. Some examples include:
- Vehicle oil & 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 city 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 nearby streams and lakes 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 further filter out these pollutants.
Last updated Feb 21, 2018