Plumbing permits in Mercer Island: fees, timeline & requirements (2026)
Everything you need to know about pulling a plumbing permit in Mercer Island, Washington — when one is required, what it costs, how long review takes, what documents are required, and which inspections you can expect. Cited to Mercer Island Community Planning & Development.
Free lookup, no account needed — the office that issues the permit at your address, cited to Mercer Island's source.
When does plumbing work need a permit in Mercer Island?
WAC 51-56 (2021 UPC) requires plumbing permit for installation, replacement, or relocation of any plumbing fixture, water heater, or piping. Like-for-like faucet replacement is exempt.
How Mercer Island adopted this rule
The threshold comes from the state code (WAC 51.56), which Mercer Island adopts by reference in the provision quoted below.
“The 2021 Edition of the Uniform Plumbing Code (UPC), as adopted and amended by the State Building Code Council in WAC Chapter 51-56, as published by the International Association of Plumbing and Mechanical Officials, is adopted by reference with the following additions, deletions and exceptions. Provided, that Chapter 1, Administration, is not adopted and the Construction Administrative Code, as set forth in Chapter 17.14 MICC, shall be used in place of UPC Chapter 1, Administration. Provided, that Chapters 12 and 14 of the Uniform Plumbing Code are not adopted.”Source ↗verified 2026-04-29
Required submittals
- Fixture count + DFU calc for repipes
- Water heater specs
- Sewer line plan if site work involved
Inspection sequence
- Rough-in / pressure test
- Final
Contractor specialties needed
Plumber
Who can do this work in Mercer Island?
Kolmo Construction is a licensed Washington general contractor — KOLMOL*753JS, active through April 10, 2027, bonded and insured — working throughout Mercer Island and King County. Kolmo manages the plumbing job from start to finish: a licensed plumbing contractor performs the work and the permit, and Kolmo coordinates the scope, schedule, inspections and any related construction. Call (206) 410-5100 for a Mercer Island plumbing quote.
Notes & caveats
From multi-jurisdiction tip sheet (Mercer Island): "Bathroom and kitchen fixture replacements without plumbing line modifications such as sinks and toilets" are exempt. However: "Tub and shower replacement does require a permit." Hose bibs and drinking fountains (per the same tip sheet) require a permit. Backflow prevention devices require a permit.
How to apply yourself
- 1. Check who issues the permit. Run an address lookup for your plumbing work in Mercer Island — we'll confirm which office issues the permit at that address.
- 2. Assemble submittals: the 3 documents under Required submittals above.
- 3. Submit through the city portal: Mercer Island Community Planning & Development ↗
- 4. Track review. Respond to reviewer comments promptly.
- 5. Pay issuance fees (Mercer Island's fee schedule sets them) and pick up the permit. Inspection card travels with the job.
Or have Kolmo do it
Kolmo runs the job: a licensed plumbing contractor does the plumbing work and pulls the permit, and Kolmo coordinates the scope, schedule, inspections and any related construction.
Licensed WA general contractor KOLMOL*753JS · bonded & insured
Plumbing permits in Mercer Island — FAQ
When does plumbing work need a permit in Mercer Island?
WAC 51-56 (2021 UPC) requires plumbing permit for installation, replacement, or relocation of any plumbing fixture, water heater, or piping. Like-for-like faucet replacement is exempt.
How much does a plumbing permit cost in Mercer Island?
With no building permit, Mercer Island prices a plumbing permit at its $46 issuance fee plus unit fees, $214 at the least: $19 for each fixture, trap or set of fixtures, $9 a fixture for repairing or altering drain or vent piping, $24 a water heater, $12 a gas piping system and $44 a building sewer. Repairing existing plumbing, water service or gas piping, or exchanging a water heater with no new gas piping, is $120. With a building permit, the plumbing inspection is part of the 31% combination fee (2026 Fee Schedule).