2.2 Showers, Shower Pans, Bathtubs, Lavatories, Bidets, & Scald Limits (UPC 407–410; WA 408)
Key Takeaways
Washington amends UPC 408.6 so a shower compartment needs at least 900 square inches and must hold a 30-inch circle up to 70 inches above the drain.
A shower dam or threshold must be 2 to 9 inches deep from its top to the top of the drain, and the receptor floor slopes 1/4 to 1/2 inch per foot (UPC 408.5).
Shower pan liners extend at least 3 inches above the finished dam, pitch 1/4 inch per foot to weep holes, and are tested by filling to the rough threshold (UPC 408.7).
Shower and tub-shower valves must meet ASSE 1016 with handle stops set to a 120°F maximum; the water heater thermostat does not count (UPC 408.3).
Minimum waste outlets are 1-1/4 inches for lavatories, 1-1/2 inches for bathtubs, and 2 inches for showers (UPC 407.5, 409.2, 408.4).
Why Bathing Fixtures Matter on the Exam
Showers and tubs combine water, heat, and hidden waterproofing. That combination produces many code dimensions: compartment size, threshold depth, liner height, pan slope, drain size, and temperature limits. Washington amends several of these rules, so read this section against the 2015 UPC plus WAC 51-56.
Showers (UPC 408)
Size, water use, and drain
| Item | Rule |
|---|---|
| Compartment size (WA 408.6) | At least 900 square inches of finished interior that can also hold a 30-inch circle. Measure at the top of the threshold, and maintain the area and circle to 70 inches above the drain. |
| Exceptions | Showers designed to ICC/ANSI A117.1, and receptors at least 30 × 60 inches |
| Allowed protrusions | Valves, showerheads, soap dishes, shelves, grab bars; fold-down seats in accessible showers may enter the circle |
| Showerhead flow (408.2) | 2.5 gpm at 80 psi in the 2015 code and 2015 Washington amendment; emergency showers are exempt |
| Waste outlet (408.4) | At least 2 inches; the strainer waterway must equal the tailpiece area |
| Washington exception to 408.4 | When a tub is replaced by a shower in a dwelling unit, a 2-inch waste is not readily available, and the AHJ approves, the outlet, tailpiece, trap, and trap arm may be 1-1/2 inches if only one showerhead is installed |
Washington difference: The unamended 2015 UPC requires 1,024 square inches. Washington reduces the area to 900 square inches but keeps the 30-inch circle. A 30 × 30-inch shower (900 sq in) passes in Washington. A 24 × 44-inch shower (1,056 sq in) still fails because it cannot hold a 30-inch circle.
Thresholds and doors (408.5)
- A finished dam, curb, or threshold must be at least 1 inch lower than the sides and back of the receptor.
- The threshold must be at least 2 inches and not more than 9 inches deep, measured from the top of the dam to the top of the drain.
- The receptor floor slopes to the drain at not less than 1/4 inch and not more than 1/2 inch per foot.
- The receptor has an integral nailing flange extending at least 1 inch above the top of the sides.
- Thresholds must accommodate a 22-inch door, and shower doors must leave at least a 22-inch unobstructed opening for egress.
Section 408.9 places controls and heads so the head does not discharge directly at the entrance. That way the bather can adjust the valve before stepping in. Section 408.10 requires the riser from the valve to the head to be securely attached.
Site-built shower pans (408.7)
- Lining height: Line the subfloor and rough walls to at least 3 inches above the top of the finished dam or threshold. Also line built-in seats to 3 inches above their horizontal surfaces.
- Pitch: Slope the lining 1/4 inch per foot to the weep holes of the subdrain, over a smooth, solidly formed subbase.
- Jambs: Carry the lining up the rough jambs and over the rough threshold, and fasten it on the outside face.
- No fasteners low: Do not nail or perforate the lining at any point less than 1 inch above the finished dam or threshold.
- Subdrain: Use an approved subdrain set flush with the subbase. It needs a clamping ring and weep holes into the waste line, and the weep holes must be protected from clogging.
| Liner material | Requirement |
|---|---|
| Plasticized PVC sheet (408.7.1) | ASTM D4551; solvent cemented joints |
| Chlorinated polyethylene (CPE) sheet (408.7.2) | ASTM D4068 |
| Sheet lead (408.7.3) | At least 4 lb per square foot, asphalt coated, joined by burning |
| Sheet copper (408.7.4) | ASTM B152, at least 12 oz per square foot; brazed or soldered |
| Hot-mopped felt | At least three layers of 15-pound asphalt-impregnated felt; corners reinforced with webbing lapped 4 inches |
Shower pan test (408.7.5): Fill the receptor with water to the level of the rough threshold. Place the test plug so that both the upper and under sides of the subpan are tested where it is clamped to the drain.
Public shower floors (408.8): Floors must be nonskid, and one bather's wastewater must not pass over areas used by other bathers. Gutters slope at least 2%, with drains no more than 8 feet from sidewalls and no more than 16 feet apart.
Scald and Temperature Limits
| Fixture | Device | Maximum |
|---|---|---|
| Shower and tub-shower (408.3) | Pressure-balance, thermostatic, or combination valve per ASSE 1016 or ASME A112.18.1/CSA B125.1 | Handle position stops set to 120°F |
| Gang showers on one tempered supply (408.3) | Mixing valve per ASSE 1069 | 120°F |
| Bathtub and whirlpool filler (409.4) | Device per ASSE 1070 or CSA B125.3 | 120°F |
| Public lavatory (407.3) | Device per ASSE 1070 or CSA B125.3 | 120°F |
| Bidet (410.3) | Device per ASSE 1070 or CSA B125.3 | 110°F |
In every case the code states that the water heater thermostat is not an acceptable control. The shower and tub-shower valve must be at the point of use and protect against both scald and thermal shock at the showerhead's rated flow.
Bathtubs and Whirlpool Tubs (UPC 409)
- 409.2: The waste outlet and tailpiece are at least 1-1/2 inches, with a stopper or strainer.
- 409.3 and 404.1: The overflow connects on the house (inlet) side of the trap. It must be arranged so standing water does not rise in it when the stopper is closed.
- 409.5: The filler is protected by an air gap or a listed fixture fitting (417).
- 409.6 Whirlpools: The access opening must allow removal and replacement of the pump. Crawl-space pump access must be within 20 feet of an access door or crawl hole. The pump sits above the crown weir of the trap, and pump and piping are self-draining.
Lavatories and Bidets (UPC 407, 410)
- 407.5: The waste outlet and tailpiece are at least 1-1/4 inches, with a stopper or strainer. Overflows follow 404.1.
- 407.2 (2015 WA amendment): Lavatory and kitchen faucets and replacement aerators are limited to 2.5 gpm. Public lavatory faucets other than metering type are limited to 0.5 gpm. Metering faucets deliver no more than 0.25 gallon per cycle (407.2.2).
- 407.4 (WA amendment): Lavatories in restrooms for the general public need self-closing metering valves. Exceptions apply where designed for persons with disabilities and in day care centers for children under 6.
- 410.2: Protect the bidet water supply with an air gap or an approved AVB, PVB, or SVB.
A contractor builds a 30-inch by 30-inch tiled shower in Washington. Under the Washington amendment to UPC 408.6, does the compartment meet the minimum size?
Yes, but only if the showerhead is limited to 1.5 gpm
No, because the unamended UPC requires 1,024 square inches
Yes, because Washington requires 900 square inches and a 30-inch circle
No, because showers must be at least 36 inches square
How is a site-built shower pan tested for watertightness under UPC 408.7.5?
Filled with water to the level of the rough threshold, with the test plug placed so both sides of the subpan are tested at the drain clamp
Filled with 1 inch of water for 24 hours
Flood test only after tile is installed
Air test at 5 psi for 15 minutes
Which device and temperature limit does the UPC require for a bathtub filler?
ASSE 1016 valve limited to 130°F
ASSE 1070 or CSA B125.3 device limiting discharge to 120°F
The water heater thermostat set to 120°F
ASSE 1069 valve limiting discharge to 110°F
Sections you finish are checked off in the contents.