3.4 Showers, Bathtubs, Fixture Fittings, and Scald Protection

Shower compartment geometry

IPC 421.4 sets two dimensions that must both be satisfied:

• Not less than 900 square inches of interior cross-sectional area, and
• not less than 30 inches in least dimension, measured from the finished interior dimension of the compartment, exclusive of fixture valves, shower heads, soap dishes and safety grab bars or rails.

The measurement is taken at a height equal to the top of the threshold, at a point tangent to its centerline, and must be continued to a height of not less than 70 inches above the shower drain outlet. In other words, a compartment that pinches in above the threshold does not comply just because it measures 30 inches at the curb.

Exception: a compartment with not less than 25 inches in minimum dimension is permitted provided it has not less than 1,300 square inches of cross-sectional area.

A 30 x 30 inch compartment yields exactly 900 square inches and complies. A 25 x 52 inch compartment yields 1,300 square inches and complies under the exception. A 28 x 34 inch compartment (952 square inches) fails — it beats the area minimum but falls below the 30-inch least dimension and does not reach 1,300 square inches.

IPC 421.4.2 Access: the shower compartment access and egress opening must have a clear and unobstructed finished width of not less than 22 inches. Compartments required to be accessible comply with IPC 404.1 and ICC A117.1 instead.

Wall and floor construction

IPC 421.4.1 requires bathtub floors, shower floors, wall areas above built-in tubs that have shower heads, and shower compartment walls to be of smooth, corrosion-resistant, nonabsorbent waterproof materials. Wall materials must extend:

• not less than 6 feet above the room floor level, and
• not less than 70 inches above the drain of the tub or shower.

Those walls must form a watertight joint with each other and with the tub or shower floor.

IPC 421.5 requires floor surfaces of impervious, noncorrosive, nonabsorbent and waterproof materials, and 421.5.1 requires floors or receptors to be laid on and supported by a smooth and structurally sound base.

Shower liners — IPC 421.5.2

Except where a prefabricated receptor is used, shower floors must be lined and made watertight. The installation rules are specific and heavily tested:

• Liners turn up on all sides not less than 2 inches above the finished threshold level.
• Liners are recessed and fastened to an approved backing so as not to occupy the space required for wall covering.
• Liners shall not be nailed or perforated at any point less than 1 inch above the finished threshold.
• Liners are pitched 1/4 unit vertical in 12 units horizontal (2-percent slope), sloped toward the fixture drain, and securely fastened to the waste outlet at the seepage entrance making a watertight joint.
• The completed liner is tested per IPC 312.9 — potable water at least 2 inches deep at the threshold, 15 minutes, no leakage.

Approved liner materials and their thresholds:

Two exceptions to the lining requirement: floor surfaces under shower heads provided for rinsing laid directly on the ground, and sheet-applied load-bearing bonded waterproof membranes, which need not be recessed.

Colorado field note: Board Rule 1.2(E)(1)(p) deletes IPC 312.9 shower liner test from the Colorado Plumbing Code, and Rule 1.2(D)(7) declares shower wall composition (421.4.1) and shower floors (421.5) to be informational only in Colorado, not subject to licensing, permitting or inspection, because they are typically not installed by plumbers. The model-code requirements still control on the exam.

Shower waste outlets and risers

IPC 421.3: shower waste outlets are not less than 1-1/2 inches in diameter. Other than in bathtubs, they must have removable strainers not less than 3 inches in diameter with strainer openings not less than 1/4 inch in least dimension. Where each shower space does not have its own waste outlet, the outlet must be located and the floor pitched so waste from one shower does not flow across the area serving another. Outlets are fastened to the waste pipe in an approved manner.

IPC 421.2: water supply risers from the shower valve to the shower head outlet, whether exposed or concealed, must be attached to the structure using support devices designed for the specific piping material or fittings anchored with screws. This is why a PEX shower riser must land in a drop-ear elbow screwed to blocking, not float free in the wall.

Scald protection — the 120-degree family of rules

This cluster is the single richest source of Fixtures and Equipment exam items. Learn which device belongs to which fixture.

Two rules that generate distractors:

• 412.3: the valve must be installed at the point of use, must be rated for the flow rate of the installed shower head, and the maximum setting is field adjusted per the manufacturer's instructions. In-line thermostatic valves shall not be used to satisfy this section.
• 412.7: an ASSE 1062 flow-reduction device shall not be used alone as a substitute for the shower valve required by 412.3 or the tub valve required by 412.5.

Fixture fittings generally

• 412.1: faucets and fixture fittings conform to ASME A112.18.1/CSA B125.1; fittings supplying drinking water for human ingestion conform to NSF 61, Section 9; flexible water connectors exposed to continuous pressure comply with IPC 605.6.
• 412.1.1: faucets and supply fittings must meet the 604.4 consumption limits.
• 412.1.2: waste fittings conform to ASME A112.18.2/CSA B125.2, ASTM F409, or a standard listed in Tables 702.1 and 702.4.
• 412.2: hand-held showers must provide backflow protection per ASME A112.18.1 or a device complying with ASME A112.18.3.
• 412.6: faucets and fittings with hose-connected outlets conform to ASME A112.18.3 or ASME A112.18.1.
• 412.8: deck-mounted bath/shower transfer valves with an integral atmospheric vacuum breaker conform to ASME A112.18.1.

Colorado field note (not exam-scored): Colorado adds 421.7, requiring shower heads to be on the sidewall of the compartment or arranged so the head does not discharge directly at the entrance and the bather can adjust the valve before stepping into the spray (roll-in accessible showers excepted); and 421.8, permitting a shower or tub/shower control valve only where the spout or head discharges into an approved tub or shower compartment, excepting emergency showers.