Most water service replacements we do around Seattle, the Eastside and south Snohomish County are trenchless, and most spot repairs are open cut. That split is not a preference. It comes from five things about the property, and once someone has located the failure the answer is usually obvious. Here is how we decide, and what each way costs.
What Each Method Actually Is
Trenchless: bore and pull
We open two small pits, one at the meter and one where the line enters the house, and run a directional drill between them beneath the lawn, the driveway and the planting. Then we pull the new line back through the bore in one continuous piece, polyethylene or PEX-A straight off the roll, with a tracer wire alongside so the plastic line can be found later. The old line stays in the ground, disconnected. On most lots the run is done in a single working day, with the water back on the same afternoon.
Open trench: expose and replace
We dig along the line's path, expose the failed section or the whole run, replace it, and put the surface back. It is the older method and still the right one in three situations: when the failure is in one known spot, when the run is short and crosses nothing but lawn, or when the line turns up inside a crawlspace where a bore cannot reach. It is also how every trenchless job begins and ends, because the two pits still have to be dug.
What Decides It on a Real Property
1. How long and how deep the run is
A short service on a flat lot can be trenched in a morning. A long one, the kind that starts at a meter by the road and ends at a house set back behind a drive on Mercer Island or in Lynnwood's older neighborhoods, is where boring pays for itself, because every extra foot of trench is a foot of yard to put back. Depth works the same way: the deeper the line, the wider and slower the trench.
2. What is sitting on top of it
Driveways, front walks, retaining walls, terraced beds and the maple somebody planted in 1978. A bore goes under all of it. A trench goes through it, and the restoration bill for concrete and mature landscaping can outrun the plumbing itself. It is the most common reason a job goes trenchless.
3. Where the failure actually is
Not every failed water line is in the yard. Around here it is just as likely to be inside the crawlspace where the service comes in, which calls for a localized repair from underneath the house, not an excavation. Under a slab, as in many 1960s and 70s Bellevue houses, the answer is usually to abandon the buried run and reroute a new line up through the floor. And a single split at a known point, at the meter or at an old clamped splice, is a spot repair by hand, not a reason to replace the run.
4. Soil, rock and what else is buried
Puget Sound glacial till is full of cobbles and the occasional boulder, and a bore that meets one can be pushed off line or stopped. We locate every buried utility before drilling, and we keep the open-cut option on the table if the ground argues. On a short, bare run in rocky ground, digging can be the cleaner choice.
5. Permits and the right-of-way
Where the run crosses the planting strip or the street, the permit picture changes. Seattle wants its own right-of-way permit for work in the street, and Bellevue requires a separate Right of Way Use Permit that a repair permit cannot cover. Trenchless keeps most of the disturbance on private property, but we pull whatever the job requires either way.
What It Costs, Honestly
The ranges we publish are the ranges we work in. A full water service replacement from the meter to the house, by either method, lands between $6,000 and $16,000 in the Seattle area. A spot repair on a line that is otherwise sound runs $2,000 to $6,000, and a localized repair on a failed section inside a crawlspace is typically $650 to $1,000.
Within the replacement range, trenchless is rarely the cheaper number on the plumbing line of the invoice, because the rig, the locates and the two pits cost what they cost. It is usually the cheaper number for the whole project, because there is no driveway to pour, no walk to reset and no yard to rebuild, and it is done in a day rather than the three to five that open excavation and restoration can take. The exception is the short, bare run: a line that crosses forty feet of lawn and nothing else can be trenched and backfilled for less, and we will say so.
Jobs We Have Done Both Ways
- On the east side of Mercer Island, a leaking black poly service became a new one-inch PEX line pulled between two pits with tracer wire alongside: that job is written up here.
- In Shoreline, a failed section sitting in groundwater seepage in a planting strip was hand-dug on purpose, one section replaced, and the turf laid back down: the Shoreline repair.
- In Kirkland, a December call turned out to be an old clamped splice letting go, cut out and rebuilt in place as a spot repair: see plumbing in Kirkland.
- In Bellevue, the failure was under the slab, so the crew opened the floor and brought a new insulated line up through it rather than boring anything: water line repair in Bellevue.
- In Lynnwood, a corroded galvanized joint in a crawlspace was rebuilt in copper from underneath the house, with no digging at all: water line repair in Lynnwood.
- In Kenmore and South Delridge, full meter-to-house replacements finished with new connections at the meter: Kenmore and Seattle water line repair.
- In Woodinville, a full replacement done the day after the estimate, in under five hours: Rebecca's story.
Questions We Get About the Two Methods
When is open trench the better choice?
When the failure is in one known spot, when the run is short and crosses nothing worth protecting, or when the line is inside the crawlspace or under the slab where a bore cannot follow it. Then a targeted dig or an inside repair is faster and cheaper, and we quote it that way rather than reaching for the rig.
Why did the trenchless quote come in higher than the open-trench one?
Because the plumbing line of a trenchless quote carries the rig, the utility locates and two pits, and it always replaces the whole run, while an open-cut quote may cover one section. Compare the totals once concrete, walks and landscaping restoration are added to the trench; on anything but a short bare run, trenchless usually wins.
What happens to the old water line when you go trenchless?
It stays in the ground. The new line follows its own bore, and the old one is disconnected at the meter and at the house and left where it lies, which is normal and harmless for a water service. Nothing has to be dug up to be thrown away, and that is a good part of why the yard survives.
Can trenchless fix a line that runs under the house?
No. A bore follows a path between two pits outside; it cannot chase a line under a slab or through a crawlspace. Under-slab failures get rerouted with a new line brought up through the floor, and crawlspace failures get repaired from underneath. Both are inside jobs, and neither should be quoted as an excavation.
Our Recommendation
For a full meter-to-house replacement on any established lot, start from trenchless and make open cut prove it is cheaper. For a single known failure on an otherwise sound line, repair the spot by hand and keep the rest. For anything under the house, stay inside: a crawlspace repair or a slab reroute, never a trench. And before anyone quotes either way, insist on the meter test and a located failure, then a repair price and a replacement price side by side. How we do that is in our water line cost guide, and the signs that a line is failing are written up here.
Ready for a Real Number?
Call 425-245-7552 for a free estimate, or request a callback. We locate the failure first, then tell you which way, and why.
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