2021 IPC Chapter 4
Lesson 3 counted how many fixtures a building needs. This lesson covers how they go in: the room each one needs, how it is anchored and sealed, what fittings it carries, and how much water it may use. Section 405 of the 2021 IPC holds the setting rules, and Sections 407 through 426 add short rules for each fixture type. Most are numbers a reviewer can check with a tape measure. These are model code numbers; Houston enforces the Uniform Plumbing Code, so confirm the adopted code before citing a section.
One sentence in Section 405.3.1 decides most toilet room layouts. A water closet, urinal, lavatory, or bidet may not be set closer than 15 inches, measured from its centerline, to a side wall, partition, vanity, or other obstruction. Where nothing separates two adjacent fixtures, their centerlines must be at least 30 inches apart. In front of the fixture there must be at least 21 inches clear to any wall, fixture, or door. An accessible children's water closet may sit 12 inches from the wall or partition on one side.
Each public or employee water closet goes in its own compartment with walls or partitions and a door (405.3.4). A single-occupant room with a lockable door needs none, and a child day care room with two or more closets may leave one open. Urinals need privacy areas too (405.3.5): 30 inches between partitions, partitions starting no higher than 12 inches above the floor and reaching at least 60 inches, extending from the wall at least 18 inches or 6 inches past the urinal lip, whichever is greater. Single-occupant and family or assisted-use rooms with a lockable door skip the partitions. In public and employee toilet rooms the required lavatory must be in the same room as the water closet (405.3.2), and piping or fixtures may not interfere with doors, windows, or egress openings (405.3.3). Accessible fixtures follow IBC Chapter 11 and the A117.1 standard (404).
Worked example: an office adds three floor-mounted closets, each in its own compartment, and four urinals with partitions. The closets need at least 3 × 30 = 90 inches of wall, plus partition thickness, and each compartment is 60 inches deep. The urinals need at least 4 × 30 = 120 inches. A room drawn at 84 inches for the closets fails before a fixture is set.
A fixture must be set level, sealed where it meets the wall or floor, and installed so the fixture and the floor around it can be cleaned (405.2, 405.3, 405.6). A floor-outlet fixture connects with a floor flange or a waste connector and sealing gasket, and the flange is anchored to the structure. Minimum flange thickness is 0.125 inch for copper alloy and 0.25 inch for plastic or cast iron, with at least 2 inches of caulking depth for cast iron (405.4.1). A wall-hung closet is carried by a concealed metal carrier fixed to the structure, so no strain reaches the fixture or piping (405.4.3). Slip joints are allowed only at the trap inlet, trap outlet, and inside the trap seal, and a concealed one needs an access panel or space at least 12 inches in its smallest dimension (405.9).
Bowls in public and employee toilet rooms are elongated, with hinged open-front seats (425.2, 425.3). Each water closet, urinal, and similar fixture needs its own flushometer valve, flushometer tank, or flush tank; one device may not serve two fixtures (415.1, 415.1.1). Flushometer valves must not be used where supply pressure is below what they need (415.2), which is why the pressure numbers in Lesson 6 matter at the fixture. Urinals may replace up to 67 percent of the required water closets in assembly and educational occupancies and 50 percent in all others (424.2). A school needing 6 closets may substitute 0.67 × 6 = 4.02, so 4 urinals; an office needing 6 may substitute 3.
| Fixture | Requirement taught | Section |
|---|---|---|
| Lavatory waste outlet | 1 1/4 in minimum, with strainer or crossbar | 419.3 |
| Bathtub waste and overflow | 1 1/2 in minimum, watertight stopper | 407.2 |
| Shower waste outlet | 1 1/2 in minimum, removable strainer at least 3 in | 421.3 |
| Shower compartment | 900 sq in and 30 in least dimension (25 in only with 1,300 sq in) | 421.4 |
| Shower opening | 22 in clear width minimum | 421.4.2 |
The shower test is arithmetic. A retrofit stall 28 inches by 34 inches has 952 square inches, which clears 900, but its least dimension is under 30, and 952 is far below the 1,300 the exception needs. It fails.
Individual shower and tub-shower valves must be balanced-pressure, thermostatic, or combination valves at the point of use, with the stop set so water cannot exceed 120°F; an in-line thermostatic valve does not qualify (412.3). Bathtub valves need a temperature-limiting device or a listed heater at the same limit (412.5). A temperature-actuated flow-reduction device at a faucet may hold 120°F at that outlet but cannot replace shower or tub valves (412.7). Public lavatories for customers, patrons, and visitors deliver tempered water, defined as 85°F to 110°F, through an approved limiting device (419.5).
| Fixture or fitting | Maximum, Table 604.4 |
|---|---|
| Water closet | 1.6 gallons per flush |
| Urinal | 1.0 gallon per flush |
| Private lavatory or sink faucet | 2.2 gpm at 60 psi |
| Public lavatory, other than metering | 0.5 gpm at 60 psi |
| Shower head (a hand-held spray counts) | 2.5 gpm at 80 psi |
Floor drains need removable strainers, access, and an outlet of at least 2 inches (413.2, 413.3); in public laundries and multifamily central washing rooms the outlet is at least 3 inches (413.4). Food waste disposers drain to at least a 1 1/2-inch line, a commercial disposer is trapped separately, and its cold water supply has an air gap or backflow preventer (416.2 to 416.4). A residential dishwasher drains to a sink tailpiece wye, the disposer, or an air break to a standpipe, looped up under the countertop (409.4). Drinking fountains are not required at an occupant load of 15 or fewer, come as a pair (one wheelchair, one standing) where required, and stay out of public restrooms (410.2, 410.3.1, 410.5).
In the field
A community center rehab replaces one restroom with a side-by-side pair. The inspector measures from the closet centerline: 13 inches to one wall, and the door swings across the 21-inch front clearance. Both fail, and both show up only after the flange is set and the tile is down. Check centerlines and door swings on the rough-in drawing before the slab is cut.
1. A plans reviewer checks a floor-mounted water closet compartment in a Group B office toilet room. Which compartment size meets Section 405.3.1?
2. An inspector measures the centerline of a floor-mounted water closet in a Group A-2 restaurant employee toilet room at 13 inches from the side partition. What is the finding?
3. Two lavatories in a Group E school toilet room sit side by side with no divider, 27 inches apart center to center. Under Section 405.3.1 the layout:
4. In a Group B single-user toilet room, the door swings in and stops 18 inches from the front of the water closet bowl. Which statement is correct?
5. A men's room in a Group A-3 community building has urinal partitions that start 16 inches above the floor and end 66 inches above it. Under Section 405.3.5 the partitions:
6. A school (Group E) needs 6 water closets. Under Section 424.2, the greatest number of urinals that may be substituted is:
7. A designer wants a partition and door around the water closet in a single-occupant Group B clinic restroom with a lockable door. Does Section 405.3.4 require it?
8. A Group M retail store is installing lavatories in public toilet facilities for customers. Which requirement applies under Section 419.5?
9. During a multifamily rehab inspection, a shower has an in-line thermostatic valve buried in the wall to meet the shower valve rule. What does Section 412.3 say?
10. A retrofit shower stall in a Group R-2 unit measures 28 inches by 34 inches. Under Section 421.4 it:
11. The central laundry room of a multifamily building has six automatic clothes washers and a floor drain with a 2-inch outlet. Under Section 413.4:
12. A new Group A-3 community hall installs a wall-hung water closet. What must support it under Section 405.4.3?
13. A specifier for a Group B office renovation lists a non-metering public lavatory faucet. What is the highest flow allowed by Table 604.4?
14. A Group B office has an occupant load of 14. Is a drinking fountain required by Section 410.2?