Main line or branch line?
This is the first thing to establish, and you can usually work it out before anyone arrives.
If one fixture is slow and everything else drains normally, the problem is in that fixture's branch line. If several fixtures are affected at once — particularly if the lowest drain in the house backs up when you run an upstairs one — the main line is the problem, because that is the only pipe they all share.
The classic test: flush an upstairs toilet and watch the basement floor drain. If water comes up there, the main line is blocked downstream of both.
What goes wrong on the main
- Root intrusion at clay joints — the most common cause in older Littleton neighborhoods
- Grease and scale narrowing the bore over decades
- Bellies where bedding has settled and the line no longer falls consistently
- Separated joints letting soil wash in
- Crushing under driveways and parking areas
- Material failure — Orangeburg deforming, cast iron corroding through
A main line stoppage is also the point at which a long-running problem finally becomes visible. Most of the ones we clear were showing warning signs for a year or more.
Where your responsibility ends
The lateral from your foundation to the city main is yours, including in most cases the portion running under the street. The city maintains the main itself. If the camera shows the blockage is in the main rather than your lateral, the repair is the city's — and the footage is what establishes that.
This is not a small distinction. It is the difference between a five-figure bill and a phone call to the utility, which is one more reason the camera run comes before anything else.
What repair looks like
Full cost breakdown.
Several drains backing up at once?
That is the main line. Stop running water and call — we answer 24 hours.
Call (303) 555-0147Questions we get asked
What is the difference between a main sewer line and a branch line?
The main line is the single lateral carrying every drain in the house to the city sewer. Branch lines are the pipes running from individual fixtures into it. One slow fixture is a branch problem. Several at once, especially the lowest drain backing up, is the main line.
How do I know if my main sewer line is blocked?
Flush an upstairs toilet and watch the lowest drain in the house, usually a basement floor drain. If water rises there, the blockage is on the main downstream of both. Gurgling from a toilet when the washing machine drains points the same way.
Am I responsible for the sewer line under the street?
In most cases yes. The lateral from your foundation to the connection at the city main is the homeowner's, including the portion under the street. The main itself is the city's. Camera footage is what proves which side a problem sits on.
Can a main line be repaired without digging up the yard?
Often, yes. Where the pipe is cracked or root-infiltrated but still round, CIPP lining or pipe bursting works through two small pits. Collapsed sections, bellies and Orangeburg need excavation.
Main line or branch?
If several fixtures back up together it is the main line, not the fixture. The camera confirms it and shows how far out the problem sits.
Platte Sewer Co. — sewer line repair in Littleton, CO. Open 24 hours.