Under house sewer line replacement in Seattle, Washington

Why it is the worst-case excavation

Under house sewer line replacement in Seattle, Washington is the job every owner hopes the camera will rule out. The building drain runs beneath the slab or through the crawlspace, collecting every fixture before it leaves the foundation, and when it fails there is a house on top of it. Replacing it the traditional way means cutting and breaking the concrete floor along the whole route, removing flooring and sometimes cabinets and walls to get there, excavating by hand or with small equipment in a confined space, hauling spoil out through the house, laying new pipe, and then compacting, pouring and finishing the floor back. The plumbing work is a fraction of the total; the demolition, restoration and displaced weeks are the rest.

Under house sewer line replacement options

• Tunneling under the slab. A pit is dug outside the foundation and a tunnel is hand-excavated beneath the footing and along the pipe route, with the old pipe removed and new pipe laid from inside the tunnel. The floor above is untouched. It is labor-intensive, limited to a practical distance from the pit, and requires care around the footing, but it keeps the demolition outside the house.
• Pipe bursting between pits outside the footprint. Where the failed run passes under the house between two points that can be reached from outside, a bursting head pulled from one pit to the other splits the old pipe in place and draws new HDPE behind it. Nothing under the slab is dug. This works when the run is reasonably straight and there are no branch connections under the house that must be reconnected.
• Lining as replacement in place. Where the pipe under the house still holds its shape, a cured-in-place liner is inverted or pulled from a cleanout, a pulled toilet or a small access hole, inflated and cured. Branch connections under the slab are reinstated with a robotic cutter. The result is a new structural pipe inside the old one, with no excavation at all.

In practice the job often uses two of these: lining for the long runs that are intact, and a small tunnel or one interior access hole at the single spot that has collapsed. A proposal for under house sewer line replacement in Seattle is rarely one method applied to the whole line, and it should say which method covers which footage.

How the choice is made from the video

The camera survey, run after the line is jetted clean, is the whole basis for the decision. The operator records each defect against the footage counter and locates it from the surface with the transmitter in the camera head, which under a slab means marking the floor. What the video shows determines what is possible. A pipe that is cracked, root-intruded, channeled or scaled but still round is a lining candidate. A joint offset by a fraction of the diameter can usually be lined; one offset by more, or a belly that holds standing water, cannot, because the liner would follow the fault. A crushed, collapsed or missing section stops both the camera and a liner and must be reached by tunnel or opened from above, or bypassed by bursting if it lies between reachable pits. The count and location of branch connections under the house matter too: each is a reinstatement for a liner and a reconnection for any replacement method. A good contractor walks through the video with the owner and points to the footage where each decision is made.

Living with the house during the job

How disruptive the work is follows directly from the method. A lining job under a slab usually takes a day or two, with the sewer out of service for the cure and the reinstatement, and the family can often stay, using fixtures sparingly once the crew says the line is open. A tunneling job runs longer, but the mess stays outside; the interior impact is the loss of drains while the pipe is out and some noise beneath the floor. A bursting job between exterior pits is similar. Full slab excavation is the one that empties rooms: flooring comes up, dust control becomes a project, and a section of the house is unusable for as long as the concrete takes to cure and be refinished. Owners in Seattle weighing a lower bid for open excavation against a trenchless bid should add the cost of the floor, the finish work and the displaced weeks to the excavation number before comparing.

What the finished job should include

Whichever method is used, the line should be filmed on completion from the access point to the connection outside the house, with the footage counter visible, and the recording given to the owner. A liner should show as a smooth continuous wall with every branch opened cleanly. A tunneled or burst replacement should show new pipe with tight joints and correct fall. A cleanout should exist or be added where the line leaves the house. A description of trenchless replacement beneath a slab shows how the trenchless options are carried out beneath a floor, and verified CIPP installers serving Seattle lists installers who have documented their under-slab lining and replacement work, which is the qualification that matters here.

When the dig is still right

There are jobs where breaking the floor is the honest answer: several collapses under a short slab, a route that needs regrading because it was never laid with enough fall, or a remodel that is opening the floor anyway. The point of the video is to make that a decision rather than a default.

Common questions in Seattle