How Do You Choose a Plumber on Mercer Island, WA?
Two things need checking, not one. In Washington the company needs a plumbing contractor license, and the person who actually turns up at your door needs a certificate of their own. Most homeowners only ever check the first, and that's the gap worth closing before you hand anyone a key.
By Ramin Shahbaziasl, Owner and Lead Plumber · Last updated August 12, 2026
What Does a Plumber Do?
The work splits three ways. There's repair — leaks, running toilets, failed water heaters, blocked drains, seized shutoff valves. There's replacement and installation, which means fixtures, water heaters, and whole-house repiping. And there's diagnosis, which is the part nobody sees and the part that decides whether the first two go well. Finding out why a drain keeps blocking, or where water is actually entering, is a different skill from fitting the part afterward.
Residential plumbing services King County WA homeowners call for tend to arrive in that order too. Something breaks, we find the cause, and the cause turns out to be older or bigger than the symptom suggested. Our general plumbing page covers the range, and if water is running right now, the emergency team is the call.
Do Plumbers Need to Be Licensed in WA?
Yes, and this is where Washington differs from most trades in a way that matters to you.
General contractors here are registered, not licensed. There's no exam. Plumbers are different. Under RCW 18.106.020, a contractor may not employ someone to engage in the trade of plumbing unless two conditions are both met: the contractor is a licensed plumbing contractor, and the person performing the work holds a journey level certificate, specialty certificate, residential service certificate, temporary permit, or training certificate. The statute also requires photo identification in their possession.
So do plumbers need to be licensed in WA? The company needs a license and the individual needs a certificate. Contractor registration on its own doesn't authorize plumbing work, which is why checking only the business is half a check.
The certificate types are worth a glance, because they aren't interchangeable. Journey level is the full ticket. Residential service and various specialty certificates are narrower. And a trainee is someone still working toward it, which is legitimate but comes with rules: under RCW 18.106.070, a trainee works under the control of a certified plumber, and that supervisor has to be on the same jobsite for at least seventy-five percent of each working day. There are limits on how many trainees one certified plumber can cover.
None of that means a trainee shouldn't be at your house. It means someone certified should be too, most of the day, and you're entitled to know which is which.
How Do You Verify It Yourself?
Free, and quicker than reading this section.
L&I publishes a public lookup, and the same tool covers both halves of the check. Search the business name at Verify a Contractor, Tradesperson or Business and you'll see registration and license status, workers' compensation standing, bond and insurance, and any lawsuits filed against the bond. You can search individuals there too.
Two habits make this stick. Do it before you invite anyone out, not after they've quoted, because it's easier to decline a stranger than someone standing in your kitchen. And ask to see the certificate on the day. Any licensed plumber Seattle Eastside homeowners hire is required to carry photo ID with it, and nobody legitimate minds being asked.
How Much Does a Plumber Cost in Washington?
The question people ask is hourly rate. It's usually the wrong question now.
Plenty of shops have moved to flat-rate pricing, where a job has a price regardless of how long it takes. Others still bill hourly. Comparing one to the other tells you almost nothing, and the quoted hourly figure hides the pieces that actually move the total: a trip or dispatch charge that applies whether or not anything gets fixed, a diagnostic fee that may or may not be credited against the work, minimum billing increments, and parts.
So how much does a plumber cost in Washington depends less on the rate than on the structure. Three questions cut through it. Is this flat rate or hourly? Is the trip charge credited if I go ahead? And is diagnosis billed separately from the repair?
After-hours work costs more, and reasonably so. What isn't reasonable is an emergency premium on work that could have waited until Tuesday. If we can talk you through stabilizing something over the phone and book you at normal rates, that's what we'll do.
What Should a Plumbing Estimate Include?
Enough detail that you could hold someone to it.
A usable estimate names the scope in plain terms — which fixture, which run of pipe, how far. It names materials and brands rather than saying "new valve." It says who pulls any permit needed and whether the fee is included. It separates labor from parts. It sets out what happens if the job opens up and turns out bigger, with a written change process rather than a verbal one. And it states the workmanship warranty in months or years.
The line that gets left out most often is restoration. On repiping and on anything inside a wall, someone has to patch drywall, match texture, and repaint. If the estimate stops at the pipe, you've been quoted half a job — and on Mercer Island, where finishes tend to be better than average, that half can be the expensive one. Our guide to repiping on Mercer Island goes into that in more detail.
Warranties, and Older Island Homes
Washington doesn't impose a statutory warranty on plumbing repairs, so what you get is what's written down. There are two separate things and people conflate them: the manufacturer's warranty on the part, which comes from the manufacturer and often needs professional installation to stay valid, and the workmanship warranty on the labor, which comes from us. Ask for the second in writing with a term attached. "We stand behind our work" isn't a warranty.
We work across the island — East Seattle, First Hill, Mercerwood, and the Island Crest corridor — and throughout the Eastside. Fixture work is on our Mercer Island page, whole-house work is on our repiping page, and the full service area is on our locations page. Recent jobs are in the gallery, with more background in our general plumbing guide for the Eastside and our emergency plumber guide. We also serve Bellevue and Kirkland, and plumbing contractors Bellevue Seattle area homeowners compare should all pass the same checks.
If you've been searching plumber Mercer Island WA, comparing the best plumbers near Mercer Island WA, or looking for the top rated residential plumbers in the Seattle Eastside, run every name through the L&I lookup first. Ours included.
Frequently Asked Questions
1. How much do plumbers charge per hour in Seattle?
Hourly rate is becoming the wrong comparison, because many shops now price flat-rate per job while others still bill by the hour, and the two aren't comparable. What moves the total is the structure around the rate: a trip or dispatch charge that applies regardless of outcome, a diagnostic fee that may or may not be credited toward the repair, minimum billing increments, and parts.
2. Do all plumbers in Washington need a state license?
Two credentials are required, not one. Under RCW 18.106.020 a contractor cannot employ someone to do plumbing work unless the contractor holds a plumbing contractor license and the individual doing the work holds a journey level, specialty, residential service, temporary permit, or training certificate, with photo identification in their possession.
3. How do I verify a Washington plumber's L&I license?
Use L&I's Verify a Contractor, Tradesperson or Business lookup, which covers both businesses and individuals. Search the business name and confirm the plumbing contractor license is active right now rather than merely on record, that the workers' compensation account is open, and that bond and insurance are in place. Check for lawsuits against the bond.
4. What should a plumbing estimate include?
Scope in plain terms, naming the fixture or the run of pipe and how far the work extends. Specific materials and brands rather than generic descriptions. Who pulls any required permit and whether the fee is included. Labor and parts separated. A written change process for what happens if the job turns out larger once opened up. The workmanship warranty with a term.
5. Do plumbers offer warranties on their work in WA?
Washington doesn't impose a statutory warranty on plumbing repairs, so you get what's in writing. Two separate things are involved. The manufacturer's warranty covers the part and often requires professional installation to remain valid. The workmanship warranty covers the labor and comes from the plumber.
Visit or Call Us
Eastside Repipe and Plumbing 12005 NE 12th St # 29 Bellevue, WA 98005 Phone: 425-331-2011 Hours: Monday–Sunday, 8:00 AM – 5:00 PM Serving Mercer Island including East Seattle, First Hill, Mercerwood, and Island Crest, plus Bellevue, Kirkland, and the Eastside.
Collecting quotes? Ask us for one or call 425-331-2011 — and check every name on your list, including ours, in the L&I lookup before you decide.
