2.1 Fixture Setting, Clearances, Closet Flanges, & Water Closets (UPC 402, 411, 413; WA 402.5)

Why Fixture Setting Is Tested

Chapter 4 questions are usually short recall items: a spacing dimension, a flange rule, a seat type, or a flush volume. Part 2 of the exam also shows fixtures on a drawing, so knowing how a water closet connects to the drainage system helps you read those drawings. This section covers the installation rules that apply to every fixture, then the water closet rules.

General Installation Rules (UPC 402)

• 402.1 Cleaning: Install fixtures for easy access for repair and cleaning. Run pipes from fixtures to the nearest wall.
• 402.2 Joints: Make the joint between a fixture and the wall or floor watertight.
• 402.3 Securing fixtures: Floor-outlet or floor-mounted fixtures are rigidly secured to the drainage connection and floor with screws or bolts of copper, copper alloy, or equally corrosion-resistant material.
• 402.4 Wall-hung fixtures: Support on metal members so that no strain reaches the connections.
• 402.10 Concealed slip joints: Provide an access panel or utility space at least 12 inches in its least dimension.
• 402.11 Future fixtures: Size drain and water piping for fixtures planned for the future, and terminate with plugged fittings.

Clearances (UPC 402.5 as Amended by Washington)

Washington's exception 2 states that paper dispensers and accessibility grab bars are not obstructions. Measure from the finished wall, not the stud. A flange set exactly 15 inches from a bare stud will fall short once drywall and tile are installed.

Exam trap: The unamended 2015 UPC applies the 24-inch front space to lavatories too. Washington's amendment applies 24 inches to water closets and bidets and allows 21 inches in dwelling and sleeping units.

Flanged Connections and Closet Flanges (UPC 402.6)

Water closets, floor-outlet service sinks, and urinals connect to the drainage pipe through an approved flange of copper alloy, hard lead, ABS, PVC, or iron. The flange may be caulked, soldered, solvent cemented, fitted with a rubber compression gasket, or screwed. The fixture is bolted down with an approved gasket, washer, or setting compound. The bottom of the flange must sit on an approved firm base. Offset, eccentric, or reducing floor flanges may not be used.

Closet rings (402.6.1):

• Approximately 7 inches in diameter, with a 1-1/2-inch-wide face to receive the gasket or seal.
• Caulked-on rings are at least 1/4 inch thick and 2 inches deep.
• Rings are burned or soldered to lead, caulked to cast iron, solvent cemented to ABS and PVC, and fastened in an approved manner to other materials.
• Closet bends or stubs are cut off smooth and even with the top of the ring before the rough inspection is called.

Fasteners (402.6.2): Closet screws, bolts, and washers must be copper alloy, copper, or other listed, equally corrosion-resistant material. They must be large enough and numerous enough to support the fixture.

Back-outlet water closets (402.6.3): The floor and wall meet at 90 degrees, with at least 5 inches of flat mounting surface on each side of the outlet centerline. The soil pipe for a floor-mounted, back-outlet water closet must be at least 3 inches. Wall-hung water closets bolt to an approved carrier fitting.

Water Closets (UPC 405, 411, 413)

• 405.1 Prohibited water closets: Any bowl with an invisible seal or unventilated space, walls that are not washed at each discharge, or a design that could siphon bowl contents back into the tank is prohibited.
• 411.1 Bowls: Bowls for public use must be elongated. Where fixtures serve children under 6, bowls must suit children's size and height.
• 411.2 Flush volume: The 2015 Washington amendment limits water closets to 1.6 gallons per flush. Continuous-flow or continuous-flush water closets are prohibited. Exceptions allowing up to 3.5 gpf cover day care bowls for young children, bowls with bedpan washers, and blowout bowls.
• 411.2.1 Dual flush: The effective volume is the average of two reduced flushes and one full flush (ASME A112.19.14).
• 411.3 Seats: Seats are smooth and non-absorbent. Public-use seats are elongated and either open-front or equipped with an automatic seat cover dispenser.

Currency note: Washington's current field code (WAC 51-56, which now adopts the 2021 UPC) limits new water closets to 1.28 gpf. L&I states the exam is based on the 2015 UPC with Washington amendments, so expect 1.6 gpf on the test.

Flushing devices (413)

• 413.1: A fixture that depends on trap siphonage (water closet, urinal, clinical sink) needs a flushometer valve, flushometer tank, or flush tank that delivers enough water to flush, cleanse, and refill the trap.
• 413.2 Flushometer valves comply with ASSE 1037 or CSA B125.3. They must be accessible for repair and self-closing, with a means of regulating flow. No manually controlled flushometer valve may flush more than one urinal. Do not use flushometer valves where water pressure is too low to operate them.
• 413.3 Flush tanks use an antisiphon fill valve (ballcock) complying with ASSE 1002. Under 603.5.2, the ballcock's critical level must be at least 1 inch above the full opening of the overflow pipe.
• 413.5: Tank overflows discharge into the water closet or urinal the tank serves.
• 603.5.1: A flushometer valve protected by an atmospheric vacuum breaker has the breaker on the discharge side. Its critical level must be at least 6 inches above the overflow rim of the bowl or the highest part of the urinal, or the distance in its listing.

Table 610.3 assigns a minimum 1-inch branch to a flushometer-valve water closet and 1/2 inch to a tank-type water closet. See Section 4.2.