One pipe, every drain

Inside the house, each sink, toilet, tub, shower and washer drains into branch lines. Those branches join a building drain under the floor or crawlspace, and the building drain leaves the house as the sewer lateral. From there the lateral runs downhill, usually under the front yard, a planter or the driveway, until it connects to the public sewer main in the street.

Because the whole house depends on that single run, a problem in the lateral shows up everywhere at once. A partial blockage slows all the drains; a full blockage sends wastewater back to the lowest opening in the house, which is often a ground-floor shower or tub.

Parts of the system, in plain words

Building drain
The horizontal pipe under the house that collects the branch lines before they leave the foundation.
Sewer lateral
The pipe from the house to the public main. Some cities call the section near the street the lower lateral.
Cleanout
A capped access fitting, often near the foundation or front yard, where a plumber can insert a cable, jetter hose or camera.
Two-way cleanout
A cleanout that allows access both toward the house and toward the street, common on newer or replaced lines.
Wye or tap
The connection where the lateral joins the public main.
Vent stack
The pipe through the roof that lets air into the drain system so water flows instead of gurgling.

Typical Whittier lateral, at a glance

Common materials
Vitrified clay or cast iron in many 1950s-70s homes; ABS or PVC where the line has been replaced
Usual route
Front of the house toward the street, often under lawn, planters or a driveway
Most common trouble
Tree roots at clay joints, cracking, scale and sagging sections
Ownership
Varies by city; confirm with the City of Whittier which section is yours

How to find your cleanout

Knowing where the cleanout is saves time in an emergency and lets a plumber start without guessing.

  1. Walk the front foundation

    Look for a short pipe with a threaded or plug cap a few inches above the soil, often near a bathroom wall or the front corner.

  2. Check planters and the yard

    Some cleanouts sit in a small box at grade, sometimes covered by mulch or ground cover.

  3. Look inside if needed

    Older homes may have a cleanout in a garage, laundry area or under a sink rather than outside.

  4. Note it for later

    Take a photo and mark the spot so anyone responding to a backup can find it quickly.

Questions to ask a plumber about your lateral

  1. What is my lateral made of, and how old does it look on camera?
  2. Where does it connect to the main, and how deep is it at each end?
  3. Is there a usable cleanout, or should one be added?
  4. Which section is my responsibility and which belongs to the city?

Common questions

Is the sewer lateral the same as the main line?

Homeowners often call the lateral the main line because it is the main drain for the house. The public sewer main is a separate, larger pipe in the street.

How long is a typical lateral?

It depends on the setback from the street and the route. A camera inspection measures the distance to each defect and to the main.

Do I need a cleanout?

A cleanout makes clearing and inspecting the line much easier. If your house has none, a plumber may suggest adding one during a repair.

General information for Whittier, not a quote or professional advice. In an emergency, call 911.