By Dawn Construction. Updated October 2026.
General information, not legal advice. Codes change. Confirm your project with City of Renton Permit Services before you start.
What rules apply to a bathroom remodel in Renton, WA?
It depends on what you change. Replacing tile, a vanity, or a toilet in the same spot is mostly finish work, but moving plumbing, adding circuits, or changing walls needs permits. Whatever you install must meet Washington rules: toilets of 1.28 gallons per flush or less, showerheads of 1.8 gpm, an anti-scald shower valve, and a vented exhaust fan.
The toilet and showerhead limits are Washington amendments to the state plumbing code. The fan rates come from the state's mechanical ventilation and energy code rules. Renton requires separate permits for electrical, plumbing, and mechanical work.
Key facts: bathroom remodel rules in Renton
| Item | Washington or Renton rule | Source |
|---|---|---|
| Toilet flush volume | 1.28 gallons per flush maximum | WA plumbing code amendment |
| Showerhead flow | 1.8 gallons per minute at 80 psi, WaterSense certified | WA plumbing code amendment |
| Several showerheads on one valve | Combined flow no more than 1.8 gpm | WA plumbing code amendment |
| Shower valve | Pressure-balance, thermostatic, or combination; hot water limited to 120°F | Uniform Plumbing Code 408 |
| Bathroom exhaust fan | 50 cfm intermittent or 20 cfm continuous | WA energy code forms |
| Tile, vanity, cabinets, countertops | No building permit (finish work) | 2021 IRC R105.2, via Tukwila |
| Electrical, plumbing, mechanical work | Separate trade permits | City of Renton |
| Asbestos survey | Required before any renovation or demolition | City of Renton |
Do you need a permit to remodel a bathroom in Renton?
Often yes, but usually a trade permit rather than a full building permit. The answer depends on the scope.
| Bathroom project | Building permit? | Trade permit? | Source |
|---|---|---|---|
| New tile, paint, vanity, mirror | No | No | 2021 IRC R105.2 |
| Replace a toilet or sink in the same spot | No | Usually no; ask Permit Services | City of Renton |
| Replace the shower valve or move the shower | Depends on scope | Plumbing permit; ask about a valve-only swap | City of Renton |
| Add or replace an exhaust fan with new ducting or wiring | No | Mechanical and/or electrical permit | City of Renton |
| Add new outlets, lights, or heated floors | No | Electrical permit | City of Renton |
| Move walls, enlarge the room, add a window | Yes | Usually trade permits too | City of Renton |
| Add a new bathroom on a septic system | Yes, plus King County approval first | Plumbing permit | City of Renton |
Renton's trade permits are over-the-counter through the online permit portal and typically issued the same day. A Residential Interior Remodel building permit typically gets a first review decision in 2 to 3 weeks. For the full step-by-step process, see our guide to kitchen remodel permits in Renton, which uses the same permit type. If you are planning the budget, see our financing options for your bathroom.
What are Washington's rules for toilets?
New toilets in Washington must use no more than 1.28 gallons per flush. The state amended its plumbing code to replace the national 1.6 gallon limit with 1.28 gallons.
This standard is called a high-efficiency toilet. When the Legislature set it, both dual-flush and single-flush toilets could qualify.
What this means for your remodel
- Check the flush volume on the box or spec sheet before you buy. It should read 1.28 gpf or less.
- Moving the toilet to a new spot means new drain work and a plumbing permit.
What are Washington's rules for showers?
Washington sets three rules most homeowners never hear about until the inspection.
Showerhead flow: 1.8 gpm
Showerheads must flow no more than 1.8 gallons per minute at 80 psi and be certified to EPA WaterSense performance criteria. The national limit is 2.5 gpm, so a showerhead bought out of state may not comply.
Multiple showerheads share one limit
If one valve controls more than one showerhead, such as a rain head plus a handheld, their combined flow cannot exceed 1.8 gpm. This affects luxury shower designs, so plan the valves before you order fixtures.
Anti-scald valves
Washington's plumbing code is based on the Uniform Plumbing Code, which requires every shower and tub-shower to have an individual control valve of the pressure-balance, thermostatic, or combination type. The valve must limit hot water to 120°F.
Newer model codes also require the valve to be rated for the flow of the showerhead installed with it. Match the valve and the showerhead so the scald protection works as designed.
| Shower component | Requirement | Source |
|---|---|---|
| Showerhead | 1.8 gpm at 80 psi, WaterSense certified | WA amendment |
| Two or more heads on one valve | 1.8 gpm combined | WA amendment |
| Shower valve type | Pressure-balance, thermostatic, or combination | UPC 408 |
| Maximum hot water at the head | 120°F | UPC 408 |
| Valve rating | Matched to the installed showerhead's flow | 2021 IPC 412.3 (model code) |
How big does a bathroom exhaust fan need to be in Washington?
A bathroom fan must move at least 50 cubic feet per minute when run on a switch, or 20 cfm if it runs continuously. Washington adds a rule: a bathroom fan sized above the continuous rate must have an occupancy or humidity sensor that turns it on automatically.
The U.S. Department of Energy's Building America Solution Center suggests choosing a fan rated at least 70 cfm to actually deliver 50 cfm through real ductwork. The fan should vent to the outdoors.
In the damp Puget Sound climate, a properly sized and ducted fan helps keep bathroom moisture under control.
What else should you check before you start?
- Asbestos survey. Puget Sound Clean Air Agency and L&I rules require one before any renovation or demolition.
- Septic systems. Adding a bathroom on a septic system needs King County Environmental Health approval before Renton approves the permit.
- Contractor licensing. Renton requires a Washington contractor license and a City of Renton business license before issuing a permit to a contractor.
- Energy code checklist. Renton asks for the 2021 Washington State Energy Code alteration checklist with interior remodel permits.
Remodeling a bathroom in Renton: local details
- Permit Center. Renton City Hall, 1055 South Grady Way. In person Monday, Wednesday, and Thursday; phone 425-430-7215 weekdays 8 a.m. to 4 p.m.
- Inspections. Book online or call 425-430-7202 for the next business day.
- Buying fixtures. Check that toilets and showerheads meet Washington's limits before ordering online.
We work across the areas we serve in King and Pierce counties.
FAQ
Can I install a 2.5 gpm showerhead in Washington?
No. Washington limits showerheads to 1.8 gallons per minute at 80 psi, and they must be WaterSense certified.
Can I have a rain shower and a handheld in Washington?
Yes, but if one valve controls both, their combined flow cannot exceed 1.8 gpm.
What size toilet flush is allowed in Washington?
New toilets may use no more than 1.28 gallons per flush. Dual-flush and single-flush toilets can both qualify.
Do I need a permit to replace a bathroom fan in Renton?
If the work adds new ducting or wiring, expect a mechanical or electrical permit. A same-size swap may not need one, so ask Permit Services.
Why does my new shower valve need an anti-scald feature?
The plumbing code requires shower valves that protect against sudden temperature swings and limit hot water to 120°F.
Do I need a permit to replace a toilet in Renton?
Renton's remodel guidance does not address a same-spot toilet swap, so ask Permit Services. Moving the toilet needs a plumbing permit.
Planning a bathroom remodel in Renton?
Dawn Construction handles bathroom remodeling in Renton and King County. Book a free bathroom estimate and we will help you pick fixtures that meet Washington's rules.
Sources
- Washington State Register WSR 21-01-125, Uniform Plumbing Code amendments (water closets 1.28 gpf; showerheads 1.8 gpm): https://lawfilesext.leg.wa.gov/Law/WSR/2021/01/21-01-125.htm
- WAC 51-51-1505, Mechanical ventilation (Washington residential code): https://lawfilesext.leg.wa.gov/law/WAC/WAC%20%2051%20%20TITLE/WAC%20%2051%20-%2051%20%20CHAPTER/WAC%20%2051%20-%2051%20-1505.htm
- City of Renton, Residential Interior Remodels: https://www.rentonwa.gov/City-Services/Permit-Services/Building-Fire-and-Signs/Residential-Interior-Remodels