2.2 Water Closets, Urinals, Bidets & Lavatories

2.2 Water Closets, Urinals, Bidets & Lavatories

Plumbing fixtures designed for personal hygiene represent the core of residential and commercial sanitation systems. Chapter 4 of the Uniform Plumbing Code (UPC) specifies strict engineering standards governing fixture construction, water consumption rates, mounting clearances, and backflow protection. Journeyman plumbers in Iowa must master these code provisions to ensure safe, functional, and hygienic installations.

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Water Closets

Water Consumption & Efficiency Standards

Federal energy legislation and UPC Section 407.1 mandate water conservation caps for all water closets:

• Maximum Flush Volume: 1.6 gallons per flush (gpf) / 6.0 liters per flush (Lpf).
• High-Efficiency Toilets (HET): Certified WaterSense models operate at 1.28 gpf (4.8 Lpf) or less, delivering a minimum 20% water reduction.
• Dual-Flush Toilets: Full flush max 1.6 gpf for solid waste; reduced flush max 1.1 gpf for liquid waste.

Bowl Geometry & Public Requirements

• Public Restroom Bowls: UPC Section 407.2 requires water closets installed for public or employee use to be of the elongated bowl type.
• Public Seats: Water closet seats in public restrooms must be made of smooth, non-absorbent materials and must be of the open-front type without a cover (UPC 407.3). This design minimizes skin contact and improves surface sanitation.
• Prohibited Water Closets: Trough water closets, washdown water closets with non-visible trap seals, and fixtures having invisible concealed fouling surfaces are strictly prohibited.

Mounting Clearances & Floor Flange Connections

• Side Clearance: Minimum 15 inches (381 mm) from the centerline of the water closet bowl to any finished side wall, partition, cabinet, or adjacent vanity.
• Total Width: A minimum clear width of 30 inches (762 mm) must be provided for the fixture compartment.
• Front Clearance: Minimum 21 inches (533 mm) clear space in front of the water closet bowl to any wall, door, or obstruction (commercial ADA layouts require 24 inches or 48 inches clear floor space).
• Floor Flange Attachment: Water closets are connected to soil piping via a 3-inch or 4-inch closet flange. The flange must be set level and securely screwed or bolted to the structural subfloor with corrosion-resistant brass or stainless steel fasteners. Closet bolts holding the bowl must be brass.

+--------------------------------------------------+
|                  FINISHED WALL                   |
+--------------------------------------------------+
                         |
                         | <-- Min. 12" (Standard Rough-in)
                         v
                 +---------------+ 
                 |  Toilet Tank  |
                 +---------------+ 
                 |  Toilet Bowl  | <-- Centerline
                 +---------------+ 
       <-----------------|----------------->
       Min. 15"          |          Min. 15"
  Side Clearance         |     Side Clearance
  (Total Compartment Width = Minimum 30 Inches)

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Urinals

Types & Flush Rates

• Standard Urinals: Maximum flush volume of 1.0 gpf (3.8 Lpf).
• High-Efficiency Urinals (HEU): Operate at 0.5 gpf (1.9 Lpf) down to pint-flush models operating at 0.125 gpf (0.47 Lpf).
• Non-Water (Waterless) Urinals: Non-water urinals are permitted under UPC Section 412.1 provided they comply with standard criteria:
  1. Incorporate a liquid trap seal cartridge containing a fluid lighter than water to block sewer gases.
  2. Feature a cleanout installed upstream or downstream within 3 feet of the drain connection.
  3. Drain into non-corrosive waste piping (ABS, PVC, or cast iron lined against uric acid corrosion).
  4. Include a capped 1/2-inch cold water rough-in behind the wall to allow future conversion to flush-type fixtures.

Backflow Protection on Flushometer Urinals

Flushometer valves connected directly to potable water supply lines represent a severe cross-connection hazard (backsiphonage of contaminated bowl water into potable lines).

• Atmospheric Vacuum Breaker (AVB): Every flushometer valve must be equipped with an AVB (conforming to ASSE 1001).
• Critical Level Installation Height: The AVB critical level (marked "C/L" on the valve body) must be installed at least 6 inches (152 mm) above the highest part of the urinal rim or flood level rim.

        Potable Water Line
                |
         +--------------+
         |  Flushometer |
         |    Valve     |
         +--------------+
                |
           =================== <-- Critical Level (C/L)
                |              ^
                |              | Minimum 6 Inches
                v              v
         +--------------+ <-- Fixture Flood Level Rim
         | Wall-Hung    |
         |   Urinal     |
         +--------------+

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Bidets

Bidets provide washing streams for personal hygiene, but present unique thermal scald and backflow hazards:

• Scald Protection Requirement (UPC 410.1): Water supplied to a bidet MUST be limited to a maximum temperature of 110°F (43°C).
• Thermostatic Mixing Valve: Temperature control must be achieved using a water temperature limiting device conforming to ASSE 1070 or CSA B125.3 installed at or near the water supply connection.
• Backflow Prevention: Over-rim water supply outlets must maintain a minimum physical Air Gap of 1 inch (or 2x supply pipe diameter) above the flood level rim. Rim-feed or submerged spray bidets must utilize an approved vacuum breaker assembly to prevent backsiphonage.

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Lavatories (Wash Basins)

Flow Rates & Waste Connections

• Residential Faucets: Maximum flow rate of 2.2 GPM at 60 psi (WaterSense standard: 1.5 GPM at 60 psi).
• Public Restroom Faucets: Maximum flow rate of 0.5 GPM at 60 psi or equipped with metering faucets delivering a maximum of 0.25 gallons per metering cycle (UPC 417.5).
• Waste Tailpiece & Trap: Lavatory outlets must be provided with a waste strainer or pop-up assembly and a minimum 1-1/4 inch (32 mm) tailpiece and P-trap.
• Public Strainers: Public lavatories typically utilize grid strainers (lacking pop-up stoppers) to prevent accidental overflow and standing water contamination.

Lavatory Overflow Provisions

If a lavatory is constructed with an overflow passage, the overflow must be designed to drain wastewater into the fixture waste outlet on the inlet side of the P-trap (above the water seal). The overflow path must be accessible for routine cleaning.