Permits and building codesPlanning

Bathroom Plumbing Code: Clearances, Shower Size and Anti-Scald Valves

By the JDI Construction teamReviewed by Arthur Kulchitskiy, Project Consultant, and Denise Lacquement, Designer (bathroom specialist)Updated October 20266 min read

Quick answer

Washington's plumbing code, the 2021 UPC with state amendments, sets a toilet at least 15 inches from its center to a side wall, 21 inches of clear space in front of fixtures in a home, a shower of at least 900 square inches that fits a 30 inch circle, a 22 inch shower door opening, anti-scald shower valves limited to 120 degrees, and showerheads of 1.8 gpm.

Washington uses the Uniform Plumbing Code, not the plumbing chapters of the International Residential Code, and it amends several of the numbers homeowners care about. That is why measurements you find in national articles are often wrong here. This page gives the Washington figures for a bathroom remodel as of October 2026, then sets them next to designer recommendations so you can see how much room the code minimum really leaves.

Which code applies

The 2021 Uniform Plumbing Code, as adopted and amended by chapter 51-56 WAC, has been in effect since 15 March 2024. The City of Vancouver lists it as "2021 Uniform Plumbing Code and WAC 51-56". Washington is finalizing its adoption of the 2024 codes, which the State Building Code Council has scheduled to take effect on 3 May 2027. Until then the 2021 codes apply. Whether the bathroom amendments below carry into the 2024 edition is not yet known.

Because the IRC plumbing chapter is replaced in Washington, rules you may read under IRC "P" section numbers (such as a 15 inch lavatory clearance or outward-swinging shower doors) are not Washington requirements.

Toilet and lavatory clearances (WA UPC 402.5)

A toilet or bidet may not be set closer than 15 inches from its center to any side wall or obstruction.
Two toilets or bidets must be at least 30 inches center to center.
Clear space in front of a toilet, lavatory or bidet in a dwelling must be at least 21 inches (Washington exception; the model code says 24 inches).
Paper dispensers and accessibility grab bars are not considered obstructions.

We found no Washington rule setting a minimum distance from a lavatory's centerline to a side wall. Concealed slip joints need an access panel or utility space at least 12 inches in its least dimension (UPC 402.10).

Shower size, curb and door (UPC 408.5, WA 408.6)

Size: "Shower compartments, regardless of shape, shall have a minimum finished interior of nine hundred (900) square inches (0.58 m2) and shall also be capable of encompassing a thirty (30) inch (762 mm) circle." The area is measured at the top of the threshold and kept clear to 70 inches above the drain, apart from valves, showerhead, soap dishes, shelves and grab bars.
Exception: the area and circle minimums do not apply to a shower receptor at least 30 inches wide and 60 inches long. Showers designed to ICC/ANSI A117.1 are also excepted.
Curb: a threshold must be at least 1 inch lower than the sides and back of the receptor, and between 2 and 9 inches deep measured from the top of the threshold to the top of the drain.
Floor slope: the finished shower floor slopes toward the drain at not less than 1/8 inch nor more than 1/2 inch per foot.
Door: "Shower doors shall open so as to maintain not less than a 22 inch (559 mm) unobstructed opening for egress."
Curbless: "Where there is a shower without a threshold, the floor space within the same room shall be considered a wet location".
Valve location: the valve and head must be placed so the showerhead does not spray directly at the entrance, "so that the bather can adjust the valves before stepping into the shower spray" (UPC 408.9).

Shower pans built on site (UPC 408.7)

A traditional site-built shower pan has a waterproof liner of sheet plastic, lead, copper or another approved material, carried "to a height of not less than 3 inches (76 mm) above the top of the finished dam or threshold". "Lining materials shall be pitched 1/4 inch per foot (20.8 mm/m) to weep holes in the subdrain". The drain sets flush with the subbase and has a clamping ring, and the weep holes must be protected from clogging. Note the two slopes: the liner below at 1/4 inch per foot, and the finished floor above at 1/8 to 1/2 inch per foot.

The code then requires a test: "Shower receptors shall be tested for watertightness by filling with water to the level of the rough threshold." Whether Vancouver accepts bonded sheet membranes or liquid-applied systems in place of a traditional liner, and how it inspects them, is something to confirm with the City of Vancouver plumbing inspector. See shower pans and bases and waterproofing explained.

Anti-scald valves and hot water limits

Every shower and tub-shower combination needs an individual control valve "of the pressure balance, thermostatic, or combination pressure balance/thermostatic mixing valve type" that provides scald and thermal shock protection, installed at the point of use (UPC 408.3). "The maximum water temperature discharging from an individual showerhead shall be limited to 120°F (49°C)". One permitted method is an ASSE 1016 valve whose limit stop or temperature control is set to that maximum (UPC 408.3.2).

Bathtub fillers have their own limit: "The maximum hot water temperature discharging from the bathtub and whirlpool bathtub filler shall be limited to 120°F (49°C)" (UPC 409.4), using a limiting device or a water heater that meets ASSE 1084. More on valve types is in shower valves and controls.

Drain sizes you will hear about

Shower: waste outlet and tailpiece at least 2 inches (WA UPC 408.4).
Washington tub-to-shower exception: a 1-1/2 inch waste, trap and trap arm may be used in a home where 2 inch is not readily available, the authority having jurisdiction approves, an existing tub is replaced by a shower, and only one showerhead rated at 1.8 gpm is installed. Ask the inspector before relying on it.
Bathtub: at least 1-1/2 inches (UPC 409.2).
Lavatory: at least 1-1/4 inches (UPC 407.5).

Each fixture needs its own trap and a vent within the code's trap arm distance; S traps are prohibited. Moving fixtures is mainly about drain and vent routes, covered in moving a toilet, shower or sink.

Washington flow limits

Fixture	Washington limit	Section
Showerhead	1.8 gpm at 80 psi, WaterSense certified	WA UPC 408.2
Several heads on one valve	Combined 1.8 gpm at 80 psi, or one outlet at a time	WA UPC 408.2.1
Bathroom faucet	1.2 gpm maximum at 60 psi; 0.8 gpm minimum at 20 psi	WA UPC 407.2.1.1
Toilet	1.28 gallons per flush, meeting WaterSense high-efficiency criteria	WA UPC 411.2

No fixture may be sold, installed or approved for installation in Washington unless it meets these standards (WA UPC 405.4). National figures of 2.5 gpm for showers and 2.2 gpm for bathroom faucets do not apply here.

Water heater items

If the remodel touches the water heater: it must be strapped "at points within the upper one-third and lower one-third of its vertical dimensions" (WA UPC 507.2). The relief valve discharge pipe must be rigid, not smaller than the valve outlet, drain by gravity, and may not discharge into a water heater pan (WA UPC 608.5). No section sets a required thermostat setting for the heater itself; the 120 degree limits apply at the showerhead and tub filler.

Code versus recommendation

The code is a floor. Designers use the National Kitchen & Bath Association's planning guidelines, which are recommendations, not code.

Item	Washington code minimum	NKBA guideline (recommendation)
Clear space in front of toilet or lavatory	21 in. (WA UPC 402.5)	At least 30 in. to any opposite fixture or wall
Toilet center to side wall	15 in.	At least 18 in.
Lavatory center to side wall	No Washington rule found	At least 20 in.
Two lavatories, center to center	No Washington rule found	At least 36 in.
Shower interior	900 sq in. and a 30 in. circle	At least 36 by 36 in.
Shower controls	Anti-scald valve, 120°F maximum	38 to 48 in. above the floor, reachable from inside and outside the spray
Grab bars	Not required in a private home	Reinforce walls at construction

NKBA's numbers were read from its guideline PDF; confirm a figure there before you build to it. Layout ideas are in bathroom layouts.

Who confirms

In Vancouver, the City of Vancouver plumbing inspector and Permit Center (360-487-7833) apply this code to your plans; in unincorporated Clark County, Clark County Community Development (564.397.4078). JDI Construction designs bathrooms to these numbers from the first layout. See our shower remodeling and bathroom remodeling pages.

Common questions

Why do national articles say a shower must be 1,024 square inches?

That is the model 2021 Uniform Plumbing Code figure. Washington amends it to 900 square inches with a 30 inch circle, and the Washington text is what applies here. National articles also often quote IRC plumbing sections, which Washington does not use.

Can I keep a 1.5 inch drain when I turn a tub into a shower?

Possibly. Washington's amendment to UPC 408.4 allows a 1-1/2 inch waste and trap in a home where a 2 inch waste is not readily available, an existing tub is being replaced by a shower, the authority having jurisdiction approves, and only one showerhead rated at 1.8 gpm is installed. Ask the inspector before you plan on it.

Does Washington require grab bars in a home bathroom?

We found no section in Washington's residential or plumbing code that requires grab bars in a private single-family home. The plumbing code does say grab bars are not obstructions for clearance purposes. Blocking in the walls during a remodel is good practice for later.

Can I install a rain head and body sprays on one valve?

Under WA UPC 408.2.1, multiple heads on one valve must have a combined flow of no more than 1.8 gpm at 80 psi, or be arranged so only one outlet operates at a time. That shapes which multi-head systems can be installed under a Washington permit.

Sources

Checked October 2026. Rules, fees and programs change; confirm the current requirement with the agency before you rely on it.