Main Sewer Line Keeps Clogging in Denver?

A cleared sewer line proves one thing: water can get through today. It says nothing about why the line stopped. When a main sewer line keeps clogging, the second or third clearing is the time to ask for a camera inspection of the clean pipe. It should answer a short list of questions before you pay for another clearing or agree to a repair.

If the line is backed up right now, stop running water in the house first. Everything below applies once it is flowing again.

Start by ruling out the City's main

Denver's wastewater FAQ says the City and County of Denver "is only responsible for main public sewers." It refers to the rest as "your private tap/service line" and recommends a licensed plumbing company for it.

The same page tells residents with a sewer backup to phone (303) 446-3400 and report it. The City says a maintenance crew will be dispatched, that Wastewater personnel will service the line if the problem is in the City sewer, and that it will tell you as soon as possible if the problem is in your private line. At that point, the City says, contacting a plumber is your responsibility.

For a line that keeps backing up, that call is worth making at least once. A restriction in the public main and a defect in your own line can produce the same symptoms in the basement, and only one of them is yours to fix.

Those rules cover properties inside the City and County of Denver. Lakewood, Westminster, Aurora, and the special districts around the metro area run their own collection systems. If your address is outside Denver's city limits, ask the sewer provider named on your bill where its responsibility ends and what number it uses for backups.

Why a second clearing does not answer the question

Elite Rooter's Denver main-line page lists four kinds of blockage: accumulated waste and paper; grease, sludge, or mineral buildup; roots in the line; and damaged or poorly aligned pipe. It adds that a break, offset joint, belly, or collapse "can hold waste and cause another backup after cleaning."

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That last group is the reason a repeat clog deserves a different visit. Paper and grease can be removed. A root mass can be cut, but the opening it came through remains. Denver's FAQ explains why: roots are drawn to the outside of a sewer line and "will penetrate the smallest crack or pin hole." A cable restores flow through the roots without closing the crack.

Clearing can restore flow whatever the cause. It does not tell you which cause you have. That takes a camera.

A customer of Elite Rooter's Westminster office described the situation in a sentence:

“This has been a repeat problem and was previously misreported by another company.”
Kaitlin M., Google review of Elite Rooter Westminster

The review does not say what the earlier report got wrong, and one account is not a pattern. It is a reason to ask for findings you can check yourself.

Seven things to get from the camera inspection

Ask for the inspection after the line has been cleared, with the pipe clean enough to see its walls. Elite Rooter's Denver camera inspection page describes a final camera pass after a cleaning to confirm the line is clear, and says customers watch the screen live while the technician explains it.

Then ask the technician about these seven points.

Seven things to get from the camera inspection
What to establish	What to ask for	Why it matters on a repeat clog
Whose line it is	A shot that ties the recording to your house, plus the access point and direction of travel	A recording with no starting point cannot be compared with the next one
Pipe material	The material at the start and at every change, such as cast iron under the house and clay or plastic in the yard	Joints and transitions are where many defects sit, and repair options depend on material
The defect itself	A clear view of what is there: roots at a joint, an offset, a crack, a low section holding water, a break, or heavy buildup	"Roots" and "collapsed pipe" lead to very different work
Distance	The approximate distance from the access point at each finding, plus nearby landmarks such as a change in pipe material or a joint	Distance counters are approximate, so landmarks help you match one inspection against another
Surface location and depth	A mark on the ground and an estimated depth from a locator, where the spot can be located	It shows whether the spot is under the lawn, the driveway, the sidewalk, or the street
How far the camera went	Whether it reached the connection at the City main, and what stopped it if it did not	An inspection that ends short of the main leaves part of your line unseen
A record	The findings in writing with the date, and whether you can have a copy of the recording	A second opinion is easier with something to show

Home inspectors work to a similar list. InterNACHI's Sewer Scope Inspection Standards of Practice, written for home inspectors, require the inspector to record the entire video and provide it to the client, to describe the pipe material when possible, and to report visible cracks, root intrusion, offsets over a quarter inch, blockages, and collapsed pipe.

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The same standard shows what a basic scope leaves out. It says the inspector is not required to locate or mark a defect, to give the length of the line, or to scope the drains inside the house. Before a repair, the location and depth matter as much as the picture. Elite Rooter's Denver camera inspection page says its technicians mark "the exact spot and depth of any problem" with a locator that reads the camera head's position from above ground, and that customers get the findings and recommendation in writing.

A Westminster customer described being shown the pipe after the clog was cleared, in a 2025 review:

“he unclogged my sewer line and then he showed me what my pipe look like and asked if I wanted the turbo jet cleaning because of all the grease in the pipes.”
Mitch S., Google review of Elite Rooter Westminster

Comparing two inspections of the same line

One clear recording of a clean pipe is often enough. Roots at a joint show where the opening is. If you also have an earlier inspection, the two together show whether the problem stays in the same place.

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Line them up from the same access point, using distance as a guide and landmarks to confirm. Roots at the same joint on both inspections point to a standing opening there, and clearing alone is likely to keep producing the same result. Debris collecting in the same low section on both points the same way. A blockage in a different place is less clear. It can mean more than one defect, or it can mean the pipe is sound and the trouble is what goes down the drain. Denver's FAQ lists what should never be flushed.

Comparison is harder when two different companies did the work. NASSCO, the industry body behind the condition codes used on public sewers, now runs a Building Sewer and Drain Inspection certification that teaches inspectors to code conditions in private lines the same way each time.

Matching the next step to the finding

Elite Rooter's Denver main-line page separates three outcomes. When the pipe is sound, drain cleaning can remove the obstruction. Breaks, offset joints, or root entry may need a local repair. A collapsed pipe or damage along a longer run may call for replacement, and the page tells customers to ask for a written scope explaining why a local repair would not resolve the problem.

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Before you approve anything beyond another clearing, ask the technician to connect the recommendation to what the camera showed:

Which finding is causing the repeat clog, and roughly where is it?
Is that spot on my property or under the sidewalk or street?
Did the camera see sound pipe on both sides of it?
What would another clearing accomplish, and how long would you expect it to hold?
Is clearing the line on a schedule a reasonable alternative to a repair here?
If you are recommending replacement of a longer run, what rules out a shorter repair?

A low section holding water raises its own questions, covered in Elite Rooter's guide to whether a sewer line belly needs to be replaced.

What Denver requires when the answer is a repair

Denver's Department of Transportation and Infrastructure publishes entrance requirements for sewer cutoff and repair under its wastewater rules. The document is dated October 14, 2022, and it is brief on repairs, but four points matter when you compare bids.

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A properly licensed plumbing or sewer contractor must do the repair, and that contractor schedules the City inspection. The permit is created when the inspection is scheduled, and the City charges a fee for each inspection. The document defines a repair as replacement of pipe in the same trench and location as the existing pipe. Rerouting a line is treated differently: a Sewer Use and Drainage Permit must be issued first, although the City inspector may approve a minor reroute in the field when the existing tap is reused.

Work under the sidewalk or street adds a step. Denver's Right-of-Way Services FAQ says a Right of Way Permit is needed any time someone is occupying or working in the right-of-way.

Ask each bidder which category the proposed work falls under, who schedules the inspection, and who pulls the right-of-way permit if one is needed. Fees and permit steps change, so confirm current requirements with DOTI Wastewater Permits at (720) 865-3060 before relying on an older quote.

Denver-area contact facts

Sewer backups inside the City and County of Denver: Wastewater Management, (303) 446-3400
Elite Rooter Westminster office: 3656 W 72nd Ave, Westminster, CO 80030, (720) 460-9944
Elite Rooter Greenwood Village office: 7939 E Arapahoe Rd Ste 230-B, Greenwood Village, CO 80112, (720) 551-7785
Phones: answered 24/7
On-site service hours: Monday through Friday, 6 a.m. to 6 p.m.; Saturday, 7 a.m. to 4 p.m.
Service area: confirm by address when you call

If the line is backed up now, stop running water and start with the Denver main-line clog page. When you call, tell us how many times the line has been cleared, when, and whether anyone has put a camera in it.

Frequently asked questions

Why does my main sewer line keep clogging?

The usual possibilities are something going down the drain that should not, a defect in your pipe that keeps catching what does, or a problem in the public main. Roots entering at a joint, an offset, a low section, a crack, or a partial collapse can all re-clog after a clearing. A camera inspection of the clean pipe is how the cases are told apart.

How many times should a sewer line be cleared before a camera inspection?

There is no fixed number. A second backup on the same line is a reasonable point to ask for one, because a repeat clog is the pattern a camera is best at explaining.

What should a sewer camera inspection report include?

The date, the access point and direction, the pipe material, each finding with its approximate distance from the access point, and how far the camera reached. Ask whether you can have a copy of the recording. For a repair, add the surface location and estimated depth of the defect.

Who is responsible for the sewer line in Denver?

Inside the City and County of Denver, the City states that it is only responsible for main public sewers. The private service line from the building to the main is the property owner's to maintain. Denver asks residents to report a backup at (303) 446-3400 so a crew can check the City sewer. Other cities and districts in the metro area set their own rules.

Do I need a permit to repair a sewer line in Denver?

Yes, in practice. Denver requires a properly licensed plumbing or sewer contractor to do the repair, and the permit is created when that contractor schedules the City inspection. Rerouting a line generally needs a Sewer Use and Drainage Permit first. Work in the street or sidewalk needs a separate right-of-way permit. Confirm current requirements with DOTI Wastewater Permits.

Sources and methodology