Leak Detection and Repair in King County, WA

Lighthouse Plumbing finds and repairs water leaks across King County from our shop in Fall City: a drip coming through a ceiling, a wet spot in a crawlspace, a water meter that never stops turning, or a water line failing under the yard. We trace the water to its source, open only what the repair needs, fix what failed and test it before we leave.

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A steel nail driven through a half-inch copper water pipe inside a wall cavity, with a streak of orange corrosion running down the pipe below it — A nail driven through a half-inch copper water line inside a closet wall, found in August by tracing a drip through the office ceiling below, in a house outside Carnation.

Real Leak Work

In August, a homeowner near Lake Marcel, outside Carnation, called about water dripping into a first-floor office. Mykal opened the ceiling where the water was coming through and found that it wasn't starting there: it was running down from the second floor. He followed it up to a closet above the office, opened the closet wall, and found the cause, a nail driven straight through the half-inch copper line that feeds the sinks in the primary bathroom. He cut out the damaged piece of copper, put in a new repair section, and tested the repair and the line around it before he left.

Looking up through an opening in a ceiling at two copper water lines, a black drain elbow and wet, stained framing above an office — The opening in the office ceiling, where the water showed up first. The pipes here were wet, but the leak itself was a floor above.

A small square opening low in a closet wall with a repaired copper water line and a black drain pipe inside, oak flooring in front and shelving rails on either side — The closet wall upstairs after the repair, with the new section of copper in place.

That job shows how a leak can travel: the water shows up wherever gravity takes it, which is often not where the pipe failed. It was one of several this summer. In early August, Mykal traced water coming through a garage ceiling outside Carnation to a shower drain that had broken away from its drain line above, and replaced the drain and trap. In July, Mykal and Bradyn found a leaking copper elbow behind the water heater in a crawlspace in Spring Glen, just east of Fall City's village, and while they were under the house they found a second leaking tee and replaced that too. In September, Alex traced a leak under the bathroom floor of a manufactured home outside Duvall to the cold-water tee feeding the toilet and sink, and replaced it with PEX and a new quarter-turn stop.

How We Find a Leak

We start at the water meter

With every faucet and appliance off, a meter that keeps moving means water is going somewhere. It cuts both ways: in July, Caleb watched a Bellevue meter for several minutes with nothing running and saw no movement at all, then opened a hose bib and watched it register at once. There was no leak to find that day, and he said so, and sent the billing question back to the utility.

We isolate before we open

Shutting off one part of the system at a time narrows the search without cutting anything. On an Issaquah call in July, Caleb shut off the irrigation and checked the crawlspace under the house, which ruled out everything except the water service coming in from the meter.

We follow the water, not the stain

Water runs along pipes, framing and drywall seams before it shows itself, so the stain on a ceiling is where the search starts, not where it ends. The office ceiling above was wet; the leak was in a closet wall upstairs.

We open small and on purpose

When the source is inside a wall or ceiling, we cut the smallest opening that will let us see and repair it.

We test the repair

We restore pressure and watch the repair and the pipe around it before we leave. New water lines are pressure-tested before they are buried or closed in.

Leaks We Repair

Inside walls and ceilings

Supply lines punctured by a nail or screw, failed fittings, shower and tub drains that have let go, and toilet seals leaking into the ceiling below. Our Issaquah leak repair page follows a slow ceiling leak that turned out to be an upstairs toilet.

Under floors and in crawlspaces

Copper elbows and tees, CPVC fittings that have turned brittle, and the connections under manufactured homes. A crawlspace leak can go unnoticed because nobody looks down there, so a damp smell, or a well pump that runs when no tap is open, is worth a call.

Underground water service lines

The pipe between the meter and the house can leak for months under a lawn before it shows. When the old line is galvanized or otherwise past saving, we replace it, usually in new 1-inch PEX-A, either by trenching or by boring under the yard with trenchless water line replacement.

Water heaters, valves and fixtures

Expansion tanks that have rusted through, relief valves, shutoffs that drip at the stem, hose bibs and supply lines. Many of these are a same-visit repair; a leaking tank itself means a water heater replacement.

Aging pipe

When a house has had more than one failure in the same kind of pipe, we put the options for a section or whole-house repipe in writing. Our Duvall leak repair page covers the CPVC found in Duvall houses from around 2000.

Leak Repair by City

We trace and repair leaks everywhere we work, and two of our city pages go deeper: water leak repair in Duvall, where aging CPVC in garage walls and crawlspaces is the common thread, and water leak repair in Issaquah, from ceiling leaks under upstairs bathrooms to a water service replaced by boring under the yard. The same approach runs from our home base in Fall City to Bellevue and the rest of the Eastside.

Frequently Asked Questions

How do I check my water meter for a leak?

Turn off every faucet, appliance and irrigation zone, then read the meter. The EPA's test is to read it before and after two hours with no water used: if the reading changes at all, you probably have a leak. By the EPA's estimate, the average household's leaks waste more than 9,300 gallons a year.

If it moves, shut the valve where the water enters the house and look again. A meter that stops is pointing at a leak inside; one that keeps going points at the line under the yard.

Can you find a leak without opening my walls?

Often we can narrow it down without cutting anything, by reading the meter, isolating parts of the system and following the water's path. Confirming and repairing a leak inside a wall or ceiling almost always takes one opening, and we keep it as small as the repair allows.

How does a nail end up in a water pipe?

A nail or screw driven into a wall can go straight through a pipe running close to the face of the framing, during construction or a later project like shelving or trim. Washington's plumbing code calls for steel nail plates where copper or plastic pipe passes within an inch of the edge of a stud or joist.

A punctured pipe can leak inside a wall where nobody sees it, and the first sign is often a stain somewhere else, as it was in the office below the closet outside Carnation.

What does it cost to find and fix a water leak?

On our 2026 invoices, tracing and repairing a single leak inside a wall or ceiling in one visit ran about $800 to $1,310, and fittings in crawlspaces, garages and attics about $600 to $1,660, tax included. Replacing a whole underground water service ran about $7,050 to $11,050.

What moves the price: how far the water traveled before it showed up, how many openings it takes to find the source, the pipe material around the failure, and, for a service line, its length and whether we trench or bore. Drywall and paint are not part of these figures.

Should I repair a leaking water service or replace it?

Repair it when the leak is one failed fitting on a line that is otherwise sound. Replace it when the pipe is galvanized or has failed before, because the rest of the line is just as old. Small yard repairs on our 2026 invoices ran about $1,090 to $1,770.