What to Do When Your Main Sewer Line Backs Up

A homeowner guide from Drain Edge Rooter, a licensed plumbing company in Rialto, CA (C-36 #1078977). Open 24/7, call anytime: (909) 927-3194.

A main sewer line backup is one of the most stressful plumbing problems a homeowner can face. The main line carries all of the wastewater from your house to the city sewer. When it clogs, water has nowhere to go but back up into the lowest drains in your home.

Signs the main line is backing up

  • Several drains are slow at the same time.
  • Water or sewage comes up in a tub, shower or floor drain when you flush a toilet or run the washer.
  • Toilets gurgle or bubble when other fixtures drain.
  • Sewage is coming out of the outdoor cleanout cap.
  • Sewer odors inside or outside the house.

What to do right away

  1. Stop using water. Do not flush toilets, run the dishwasher or washing machine, or take showers until the line is cleared.
  2. Tell everyone in the house to stop using water too.
  3. Keep children and pets away from any sewage, and avoid touching it without gloves.
  4. If sewage is near electrical outlets or appliances, stay out of the water and shut off power to that area only if you can do it safely.
  5. Find your sewer cleanout, usually a capped pipe outside near the foundation or in the front yard. A plumber will usually clear the line from there.
  6. Take photos for your insurance company.

Common causes

  • Tree roots growing into joints of older clay or cast iron sewer lines.
  • Grease, wipes and paper products building up in the line.
  • A sag (belly) in the pipe where waste settles.
  • A cracked, separated or collapsed pipe.
  • In homes from roughly the mid-1940s through the 1960s, deformed Orangeburg (tar-paper) pipe.

Many older Inland Empire neighborhoods have mature trees and original clay or cast iron sewer laterals, so root intrusion is a common cause.

New ABS sewer line installed in a trench through root-filled soil by Drain Edge Rooter
Roots are a common cause of main line backups. This new sewer line runs through root-filled soil.

How a plumber clears the line

A plumber will usually run a cable machine through the cleanout to open the clog. Grease and heavy buildup may call for hydro jetting, which uses high-pressure water to clean the pipe walls. Jetting is not right for every pipe; fragile or deformed lines should be inspected first.

Why a camera inspection matters

Clearing the clog gets water flowing, but it does not tell you why it happened. A sewer camera inspection shows roots, cracks, sags and the pipe material, so you can decide whether the line needs routine maintenance, a repair, lining or replacement. Lining can work on many clay and cast iron lines, but Orangeburg pipe cannot be lined or rehabilitated. It has to be dug up and replaced.

Preventing the next backup

  • Only flush toilet paper.
  • Keep grease out of the kitchen sink.
  • Know where your cleanout is and keep it accessible.
  • If you have recurring root problems, ask about a maintenance schedule or a permanent repair.

How to find your sewer cleanout

Most homes have a sewer cleanout, a capped pipe that gives access to the main line. Look outside along the foundation on the side of the house closest to the street, near the front yard, or near where the bathrooms are. It is usually a short white, black or cast iron pipe with a threaded cap, often three or four inches across. Some older homes have a cleanout inside, in a crawlspace or under a sink, or none that is easy to reach.

If water or sewage is coming out of the cleanout, the clog is between the cleanout and the city sewer. If the cleanout is dry when fixtures back up, the clog may be between the house and the cleanout. Do not remove a cleanout cap on a full line yourself; the pressure can release sewage suddenly. If your home has no accessible cleanout, a plumber can recommend adding one.

New ABS sewer line with a two-way cleanout installed in a trench by Drain Edge Rooter
A two-way cleanout gives access to the main line in both directions.

When to call a pro

A main line backup is a job for a plumber. Drain Edge Rooter is open 24/7, so call anytime at (909) 927-3194. We will talk through what is happening and give you a straight answer on timing.

Related services and areas

Related services: Sewer Backup Help, Drain Cleaning, Hydro Jetting, Sewer Camera Inspection. We serve the whole Inland Empire, including plumber in San Bernardino, plumber in Colton, plumber in North Riverside, plumber in Upland. See all homeowner plumbing guides.

What to Do When Your Main Sewer Line Backs Up: FAQ

Is a sewer backup the city's responsibility?

In most cases, the homeowner is responsible for the sewer lateral from the house to the city connection. If the city main is backed up, contact your city sewer department.

Can I use a plunger on a main line clog?

Plunging rarely clears a main line clog and can push sewage out of other drains. Stop using water and call a plumber.

Why does my tub fill up when I flush?

The tub is usually the lowest drain, so when the main line is blocked, wastewater backs up there first.

Will the clog come back?

It can, especially with roots or a damaged pipe. A camera inspection shows the cause so it can be addressed.

Need help?

Drain Edge Rooter is open 24/7, so call anytime at (909) 927-3194. We will talk through the problem and give you a straight answer on timing.

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