When the tub, the toilet and the downstairs sink slow down together, the shared drain inside the house is narrowing. We clear it from an indoor cleanout, prove it flows, and check whether the problem keeps going out into the side sewer.
Owner answers 8 AM to 8 PM, seven days · Book online 24/7

The short answer
Main drain cleaning clears the building drain, the shared pipe inside the house where branch lines join before it leaves the foundation. When it narrows, several fixtures slow together, often on the lowest floor first. We clear it from an indoor cleanout, flow-test it and check whether the problem continues into the side sewer. Seattle price: $200–$600 flat.
$200–$600
Building drain cleared, flat price
Inside first
Cleared from the indoor cleanout
$0 trip fee
Same rate evenings & weekends
This page is for the shared drain inside the building. A blockage out in the yard or under the street is a different line and a different job.
We open the indoor cleanout, clear the building drain with a cable sized for it, and run water through every affected fixture to prove it. If the restriction continues past the foundation, we say so and price the side sewer separately.
In older houses the problem is often the pipe wall, not something stuck in it. If the cable comes back with rust flakes and scale, the next step is a camera and possibly cast iron descaling.
Three different pipes, three different jobs. The pattern of what is slow tells us which one before we arrive.
| What you notice | Which line | The right service |
|---|---|---|
| One sink, tub or toilet is slow; nothing else is | Which lineThat fixture’s branch line | The right service Clogged drain service |
| Several fixtures inside slow together; nothing outside | Which lineThe building drain | The right serviceMain drain cleaning, this page |
| Lowest-floor shower or floor drain gurgles when upstairs drains | Which lineThe building drain, near its low end | The right serviceMain drain cleaning, with a camera if it repeats |
| Water at the basement floor drain or a yard cleanout | Which lineThe side sewer outside | The right service Main sewer line cleaning |
| Everything backs up, worse during rain | Which lineThe side sewer, sometimes the public main | The right serviceMain sewer line cleaning and a call to SPU |
Still not sure? The free drain diagnostic walks through it.
Inside the house the causes are different from out in the yard. These are the ones we find most.

01
Many older homes still have cast iron building drains. Cast iron rusts from the inside and builds a rough scale that narrows the pipe and grabs debris, which is why it slows down even when nothing is stuck in it.
02
Laundry lint, soap and kitchen grease travel down separate branches and meet in the building drain. That junction is where they settle and harden.
03
Seattle Public Utilities lists structural deterioration due to aging pipes among the causes of side sewer damage. The building drain inside the house is usually the same age.
Source: SPU, Side Sewer Defects & Issues04
An N.C. Cooperative Extension urban forester notes that highly caustic drain cleaners can damage older sewer pipes. In a scaled cast iron drain they mostly sit in the low spots.
Source: N.C. Cooperative ExtensionIndoor access, the right cable and a camera when the cause is not obvious.
Clearing from inside reaches the building drain directly and keeps the work off your lawn.
A building drain is larger than a sink branch; the cable and head are matched to it.
If the drain slows again within months, the camera shows whether it is scale, a sag or the side sewer.




The names sound alike and some companies use them interchangeably. They are different pipes, and the difference changes the price.
| What to check | Main sewer line cleaning | Main drain cleaning |
|---|---|---|
| Which pipe | The side sewer, foundation to city main | The building drain inside the house |
| Usual access | Outdoor cleanout | Indoor cleanout or a pulled toilet |
| Typical cause | Roots at joints, grease, offsets | Scale in cast iron, lint, soap and grease |
| Who owns it | The owner, all the way to the main | The owner |
| Seattle price | $200–$600; $500–$700 jetted | $200–$600; $500–$700 jetted |
One visit for most building drain clogs, with a camera when the cause is not obvious.
3–5 min
Which fixtures are slow, which floor, and whether anything shows up outside.
Same day
A window, not a whole day, when the schedule allows.
~10 min
Indoor access found, floors covered, one price approved first.
30 min–2 hrs
Cable sized to the building drain, from the closest access.
~15 min
Every affected fixture run; camera if the line is cast iron or it repeats.
Book a slot online any hour, or call and the owner answers 8 AM to 8 PM. Same flat price evenings and weekends.
Water coming up a floor drain? Call (206) 590-1455
A flat price for the shared drain inside the house, cleared from inside.
Our flat price
$200–$600
The building drain, cleared from inside
Main drain cleaning costs $200 to $600 in Seattle, flat, for the building drain inside the house. We clear it from the indoor cleanout, or a pulled toilet when there is none, and run every affected fixture to prove it. If the line needs jetting, that is $500 to $700.
Flat Seattle prices for clearing the building drain and fixing why it narrowed.
The side sewer from the house to the public main, cleared and checked on camera.
$200–$600
Chain knockers strip rust and scale from inside old cast iron, with no digging.
From $800
HD camera from the cleanout toward the main, every defect located by distance, footage yours.
$300–$400
4,000 PSI water scours grease, scale and root hair off the pipe wall after a camera pass.
$500–$700
Inside or outside the foundation, the drain is the owner’s responsibility. Here is where that ends.
The building drain and every branch line inside the house belong to the property owner.
Seattle Public Utilities says the owner’s side sewer runs until it connects to the public sewer main, including under the sidewalk and street. SPU: Your Side Sewer
For a blockage in the public main or the city connection, call SPU at (206) 386-1800, 24 hours a day. SPU: Side Sewer Backups
Washington L&I lists every registered contractor. Verify a contractor; ours is #DRAINDA756MA.
Drain cleaning near you
Same flat prices across Seattle, the north end and the Eastside. See all service areas.
What the main drain is, how it differs from the sewer line, and what it costs. More in the Seattle drain & sewer FAQ.
Still have a question?
Shane answers the phone himself, 8 AM to 8 PM, seven days a week.
The main drain, or building drain, is the shared pipe inside the house where the branch lines from sinks, tubs, toilets and the laundry join before the pipe leaves the foundation. Outside the foundation it becomes the side sewer, which runs to the city main.
Ours runs $200–$600, flat, from an indoor cleanout. If the line is coated in grease or scale and needs hydro jetting, that runs $500–$700. There is no trip fee, and evenings and weekends cost the same.
Main drain cleaning clears the building drain inside the house. Main sewer line cleaning clears the side sewer outside, from the foundation to the city main. Several fixtures slow inside with nothing outside points to the building drain; water at the basement floor drain or a yard cleanout points to the side sewer.
Several fixtures inside the house slowing together, usually the lowest ones first, a toilet that gurgles when a nearby tub or sink drains, and water appearing in a lower-level shower or floor drain.
Many older houses have cast iron building drains. Cast iron rusts from the inside and builds a rough scale that narrows the pipe and catches debris, so the line slows down even when nothing is stuck in it. A camera shows whether scale is the cause.
Often, through a removed toilet or another access point. We tell you before pricing which access we would use, and whether adding a cleanout would make future cleanings easier.
No. We clean, jet and descale drain lines and run cameras. If the pipe has failed, we refer the repair with the footage, so you know exactly which section needs it.
Ownership rules and outside guidance on this page come from these public sources. Our prices are flat Seattle rates for standard service, reviewed October 2026.
Which fixtures, which floor and whether anything shows up outside tells us building drain or side sewer before we arrive.
The Drain Authority
5608 17th Ave NW, Suite 2025