Washington licenses both the plumbing business and the individual plumber, and the two are checked separately. A few minutes on the state’s Verify tool, plus a written contract and a sensible payment schedule, protect you from most of the problems the Department of Labor & Industries (L&I) hears about.
The plumbing contractor license
Since July 1, 2021, it has been unlawful to advertise, bid or do plumbing work without a plumbing contractor (PC) license from L&I (RCW 18.106.400). Before then, plumbing businesses registered as general construction contractors. The PC license replaced that, and a licensed plumbing contractor doesn’t also need a construction contractor registration.
To get and keep a PC license, a business must have:
- A designated plumber. It must employ a full-time plumber holding a journey level certificate, or a specialty certificate covering the work it does. No one may serve as the certified plumber for work beyond the scope of their own certificate.
- A $6,000 surety bond (RCW 18.106.410). A homeowner suing the bond for breach of contract must file within two years of the work being substantially completed or abandoned. Claimants other than residential homeowners can be paid no more than half the bond.
- Liability insurance of at least $50,000 for property damage, $100,000 for injury to one person and $200,000 for injury to more than one person (RCW 18.106.420).
If the bond or insurance lapses, the license is suspended automatically. A PC license lasts 24 months.
Side sewer and drain companies are different. Plumbing, as defined in state law, is work on water and waste systems “within a building.” L&I says certification is not required for work outside a building, such as sewer connections. Those companies register as construction contractors instead, with a $30,000 bond for general contractors or $15,000 for specialty contractors (RCW 18.27.040). The relevant specialties are side sewers (SU) and drain cleaning (RK), which covers camera inspection, cleaning and snaking but not replacing damaged parts (WAC 296-200A-016).
Plumber certificates
Everyone doing plumbing for pay must hold a certificate (or a trainee card) and carry photo ID. L&I requires plumbers to wear and display the certificate on the job. Trainees must be supervised by a certified plumber.
| Certificate | What it allows |
|---|---|
| Journey level (PL01) | All phases of plumbing construction |
| Residential (PL02) | Installation, maintenance and repair in single-family homes, duplexes and apartment buildings up to three stories |
| Residential service (PL04) | In single-family homes and duplexes only: servicing, repairing or replacing existing fixtures, piping and fittings outside the interior wall or above the floor. In any residential structure: drain cleaning, and leak repairs from the leak to the next serviceable connection. No new construction of any kind |
| Pump and irrigation (PL03), domestic well (PL03A) | Water pumping and treatment equipment; also need electrical certification |
| Backflow (PL30) | Maintenance and repair of existing backflow assemblies inside a building, not installing or replacing them |
A company whose designated plumber holds only a PL04 certificate is limited to that scope. If you need a remodel, a repipe or new fixtures in new locations, look for a PL01 or PL02.
How to check a plumber on L&I Verify
- Go to L&I’s Verify tool and search by business name, license number or UBI number. The law requires the registration number to appear in contractors’ advertisements, and L&I says you can find it on your written bid.
- For a plumbing business, look for an active Plumbing Contractor license and check the expiration date.
- L&I says the Verify tool shows whether the contractor is bonded, has liability insurance and has outstanding infractions. Check the bond and insurance are current.
- Look up the individual plumber’s certificate too, and check it covers your job.
How this directory checks. A listing appears under plumbing only with an active PC license of specialty 01, 02 or 04. Each license is checked automatically with L&I before it is published and again every week. It must be active, of the type and specialty the listing claims, and, for plumbing contractors, have a current bond, current insurance and an active designated plumber. Side sewer listings need an active side sewer or general contractor registration. Details are on our about page. Listings are not endorsements, and nobody pays to be listed.
Permits are local
- Who issues them. L&I says building and plumbing permits are issued by the county or city where the work is. In Seattle, plumbing inside a building is permitted and inspected by Public Health – Seattle & King County, and side sewers by Seattle Public Utilities.
- Who pulls them. L&I says that in most cases, if you have hired a contractor, the contractor is required to take out the permits. It lists a contractor asking you to get the permit as a warning sign.
- License check at the counter. Cities and counties must verify that a contractor is currently licensed before issuing a plumbing permit, and print the PC license number on it (RCW 18.106.440).
- Inspections. L&I advises making sure the contractor requests inspections before work is covered up, and keeping copies of permits and inspection results.
Contracts, disclosure statements and liens
- Get bids and a contract in writing. L&I recommends comparing several written bids on scope, warranties, products, dates and price, and checking that permit fees and taxes are included.
- Disclosure statement. For residential repair or construction of $1,000 or more, RCW 18.27.114 requires the contractor to give you a disclosure statement before work starts. It explains that unpaid suppliers or subcontractors may lien your property, and that you can ask for lien release documents. A contractor that doesn’t provide it can’t maintain a lien claim. The statute is in the construction contractor chapter, so ask any contractor for it, including a plumbing contractor.
- Lien notices. Under RCW 60.04.031, suppliers and subcontractors who don’t contract directly with you must send you a notice of their right to claim a lien. For repairs or remodels of an owner-occupied single-family home, their lien is limited to what you still owe the contractor when the notice arrives. L&I says to take a lien notice seriously, tell your contractor, and find out how the sender will be paid.
- Lien releases. Before the final payment, L&I advises getting lien releases from all major subcontractors and suppliers.
Deposits and payments
We found no Washington law setting a maximum deposit. L&I’s advice:
- Pay a reasonable down payment, then pay as specific phases are completed, not on a calendar.
- Withhold part of the payment until all the work is complete.
- Get a receipt for every payment.
- Treat cash-only demands, large deposits, full payment up front, or payment to a person rather than the business as warning signs.
Doing your own plumbing
RCW 18.106.150 says you don’t need a license to do plumbing at your own residence, farm or place of business, or on other property you own. Friends, neighbors and relatives may help, as long as none of them holds out as being in the plumbing business. The law does not set aside local plumbing codes, so permits and inspections still apply. The contractor-license exemption for your own residence does not apply to a building that is for rent, sale or lease (RCW 18.106.400).
If something goes wrong
- Bond claim. L&I says that for unfinished or defective work you can file suit against the contractor’s bond.
- Insurance claim. For damage caused by the contractor’s negligence, contact the contractor’s insurer. Verify shows the policy and amount.
- Homeowner Recovery Fund. From July 1, 2026, L&I can pay up to $25,000 per contractor per parcel to owner-occupants of a single-family home or a building of up to four units (not condos). You need a final superior court judgment, ordered after July 1, 2026, against a registered contractor, and you must first pursue the contractor’s bond. Apply within 90 days after the court case ends. Payment depends on available funds, and there is a waitlist. The fund is written for contractors registered under RCW 18.27, so if your claim is against a plumbing contractor licensed under RCW 18.106, ask L&I whether it qualifies.
- Report fraud. Report unlicensed or fraudulent contractors to L&I online or at 1-888-811-5974. L&I’s contractor information line is 1-800-647-0982.
- Attorney General. The AG’s office offers informal complaint resolution and asks the business to respond within 30 days. It cannot force a business to resolve a complaint or act as your lawyer. Small claims court is the main alternative.