Parts of a Sewer System – From the House to the River

All 11 parts on the diagram

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The street 6

Lateral (building sewer) The pipe from one building to the sewer under the street.
Cleanout A capped opening for reaching into the pipe to clear a blockage.
Sewer main The pipe under the street. It collects wastewater from many buildings.
Manhole An opening that lets workers and equipment reach the sewer.
Storm drain inlet Rain water from the street runs in through its grate.
Storm sewer A separate pipe for rain water. It leads to a stream or river, not to the plant.

To the river 5

Interceptor A large sewer that collects the flow from the mains. It leads toward the treatment plant.
Lift station A pumping station. It lifts wastewater to a higher level.
Force main A pipe that carries wastewater under pressure from a pump.
Treatment plant Wastewater is cleaned here before it goes back to a river.
Outfall The place where the cleaned water is let out into the river.

How this list was compiled: Every name checked on 2026-10-01, a name kept only where two independent sources use it: the US Environmental Protection Agency's Primer for Municipal Wastewater Treatment Systems, glossary, https://www.epa.gov/sites/default/files/2015-09/documents/primer.pdf (lateral sewers, main, trunk and interceptor sewers, sanitary sewer, storm sewers, treatment plant), and its page on combined sewer overflows, https://www.epa.gov/npdes/combined-sewer-overflows-csos (outfalls; one combined pipe); a state university's field training manual for sewer operators, volume 1, glossary and chapter 3, https://archive.org/details/micro_IA41153345_0683 (building sewer or house connection, lateral sewer, cleanout, main sewer, manhole, intercepting sewer or interceptor, lift station, force main, inlet and catch basin, storm sewer, outfall); Wikipedia, Sanitary sewer and Storm drain, text only, https://en.wikipedia.org/wiki/Sanitary_sewer and https://en.wikipedia.org/wiki/Storm_drain (laterals from each building, mains and trunk sewers, manholes, interceptors, lift station, force main, storm drain inlets and catch basins, storm sewer); and a plumbing estimating book read through archive.org's full-text search, https://archive.org/details/estimatingplumbi0000mass (sewer lateral, two-way cleanout). Not an official EPA publication. Licence: own work

The drawing: Drawn for this site on 2026-10-01 from plain geometry; not any town's system, nothing traced. Licence: own work

How it works

The parts of a sewer system carry wastewater from a building to a treatment plant. The first drawing shows a house and its street, cut through the ground. The second follows the pipes to the river.

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Follow the water

Wastewater leaves the house through the lateral, which has a capped cleanout near the house, and runs down to the sewer main under the street. A manhole reaches the main from the road. Rain takes another path: it drops through the storm drain inlet at the curb into the storm sewer. In the second drawing the main empties into a large interceptor. At the low point a lift station pumps the flow up through a force main to the treatment plant, and the cleaned water leaves through the outfall.

Names differ from town to town. The lateral is also called the building sewer, and a lift station a pump station.
In some older cities one combined sewer carries both rain water and wastewater in a single pipe.

Questions and answers

What are the parts of a sewer system?

A lateral carries wastewater from each building to the sewer main under the street. Mains feed a larger interceptor, which leads to the treatment plant. Manholes give a way in, and lift stations pump the flow uphill through a force main.

What is the difference between a sanitary sewer and a storm sewer?

A sanitary sewer carries wastewater from buildings to a treatment plant. A storm sewer is a separate system of pipes that carries rain and melted snow from streets and yards to streams and rivers.

What is a lift station in a sewer system?

A pumping station. Sewers usually flow downhill by gravity. Where the land ahead is higher, or the pipe would have to be buried very deep, a lift station pumps the wastewater up through a force main.

What is a sewer lateral?

The pipe that connects one building to the sewer main in the street. It is also called a building sewer or a house connection. A capped cleanout gives a way into it.