2021 IRC Chapter 27
Chapter 27 of the IRC sets the physical dimensions and connection rules for the fixtures a GCHS inspector sees in nearly every rehab bathroom and kitchen: how much clearance a water closet needs, how small a shower can legally be, what stops a tub or shower valve from scalding someone, and how a dishwasher is allowed to discharge into the drain. None of this is about GCHS installing fixtures; it is about knowing, when a licensed plumber's rough-in or a finished bathroom layout comes across an estimate or an inspection, whether the numbers actually clear code.
P2705.1 sets the clearance around water closets, lavatories, and bidets. A fixture may not be set closer than 15 inches from its center to any side wall, partition, or vanity, or closer than 30 inches center to center from an adjacent fixture, and there must be not less than 21 inches of clearance in front of it to any wall, fixture, or door. The 15-inch side clearance and the 21-inch front clearance apply to each fixture separately, so passing one does not excuse falling short on the other. A tight rehab bathroom that reuses an old footprint is the single most common place this clearance comes up short, because older houses were often built to looser local rules than the current code.
The same P2705.1 numbers govern lavatories and bidets: 15 inches from the fixture's center to a side wall, partition, or vanity, 30 inches center to center between adjacent fixtures, and 21 inches clear in front. P2705.1 also requires that a fixture be usable and that its location not interfere with the operation of windows or doors. A pedestal lavatory shoved into a corner to make room for a wider shower is a common value-engineering move in a rehab bid, and it is worth checking against the 15-inch rule before it is priced, not after the tile is set.
P2708.1 sets the minimum size of a shower compartment at not less than 900 square inches of interior cross-sectional area, with no dimension less than 30 inches, measured from the finished interior dimension at a height equal to the top of the threshold and continued up to at least 70 inches above the drain outlet. The measurement is exclusive of fixture valves, shower heads, soap dishes, and safety grab bars or rails. The code allows a narrower stall, down to 25 inches in its smallest dimension, only if the compartment provides at least 1,300 square inches of area to make up for it. A fold-down seat is allowed as long as the 900 square inches is maintained with the seat folded up, so a built-in bench or curb that eats into the footprint means the shower does not meet the minimum even if the plans show a bigger number. The compartment's access and egress opening must be at least 22 inches wide, hinged shower doors open outward, and the drain outlet must be at least 1-1/2 inches in diameter.
P2708.4 requires individual shower valves, and tub-shower combination valves, to be a balanced-pressure type, a thermostatic type, or a combination of the two, conforming to ASSE 1016 or the equivalent ASME A112.18.1/CSA B125.1 standard, rated for the flow of the installed shower head and installed at the point of use. Each valve must have a means to limit its maximum setting to 120 degrees Fahrenheit, adjusted in the field per the manufacturer's instructions, and an in-line thermostatic valve does not satisfy the section. This is not the same thing as turning the water heater thermostat down to 120 degrees, which lowers stored hot water capacity without actually limiting what comes out of a mixed shower valve if the cold supply fails or a toilet flushes elsewhere in the house. The valve itself has to compensate for pressure or temperature swings and cap the outlet, which is why a rehab that reuses an old two-handle shower valve without upgrading it is a common and serious code gap, since older two-handle valves generally do not provide this protection at all. Bathtub-only and whirlpool bathtub valves fall under P2713.3 instead: they must have or be supplied by a water-temperature-limiting device conforming to ASSE 1070 (ASME A112.1070/CSA B125.70), set to a maximum of 120 degrees Fahrenheit, with access provided to the device unless it is a nonadjustable one built into the fixture fitting.
In the field
GCHS inspectors see this gap most often in an older house where the tub surround has been retiled around the original two-handle valve to save money, leaving the compliant-looking tile job sitting on a valve with no scald protection at all. Because the valve body is concealed once the tile is set, catching this has to happen at rough-in, when the valve's listing label and type are still visible, not at a final walkthrough where only the trim is visible.
P2720 covers whirlpool bathtub installations specifically, in addition to the general bathtub and valve rules. Access has to be provided to the circulation pump in accordance with the fixture or pump manufacturer's installation instructions. Where those instructions do not give the location and size of a field-fabricated access opening, the opening must be at least 12 by 12 inches, and at least 18 by 18 inches where the pump is more than 2 feet from the opening. A door or panel may close the opening. An access panel is not an optional nicety; a whirlpool tub installed without one is a routine finding in rehab work, usually because the tub deck was framed and finished before anyone thought about how the pump would ever be reached again. P2720.2 also requires the pump to sit above the crown weir of the trap, with piping graded so the pump drains after use.
Table P2903.2 in Chapter 29 caps the maximum flow of fixture fittings: showerheads at no more than 2.5 gallons per minute at 80 psi, lavatory faucets and sink faucets at no more than 2.2 gallons per minute at 60 psi, and water closets at no more than 1.6 gallons per flushing cycle. A hand-held shower spray counts as a showerhead. These are maximums, not targets, and many WaterSense-labeled fixtures are voluntarily rated lower, which matters for a GCHS estimate because a homeowner or program funder may specifically want WaterSense fixtures specified rather than merely code-minimum ones. GCHS does not verify a fixture's rated flow with a test gauge in the field; the practical check is the fixture's own label or cut sheet against what is specified.
P2717 covers dishwashing machines, and the drain side is the part inspectors check most. The water supply to a dishwasher has to be protected against backflow by an air gap built into the machine or by a backflow preventer (P2717.1). On the drain side, the combined discharge from a dishwasher and a one- or two-compartment sink, with or without a food waste disposer, is served by a trap at least 1-1/2 inches in outside diameter, and the dishwasher discharge pipe or tubing has to rise to the underside of the counter and be fastened there before it connects to the head of the disposer or to a wye fitting in the sink tailpiece (P2717.2). That rise is the high loop, and it keeps sink wastewater from running back into the machine. Some jurisdictions require an air gap device on the drain side by local amendment, so check the adopted code. Where the dishwasher drains through a food waste disposer, the disposer's factory knockout plug for the dishwasher inlet has to be removed before the hose is connected, a step that is easy to skip during a swap-out and shows up later as a dishwasher that will not drain. A clothes washer is different: its discharge goes through an air break (P2718.1).
Beyond shower and tub valves, a range of fixture fittings, including hose bibb vacuum breakers, flexible water connectors, and certain faucets, are required to be listed to an applicable ASSE or ASME standard (Table P2701.1). Each pipe, fitting, fixture, and device also has to carry the manufacturer's identification and the markings its standard requires (P2609.1), and products required to meet a standard must be listed by a third-party certification agency (P2609.4). For a GCHS inspector, the practical check is rarely memorizing every standard number; it is confirming that the fitting carries a legible listing mark at all, and that the mark matches the type of protection the situation calls for, such as an ASSE 1016 shower valve rather than an unmarked or purely decorative one. An unmarked fitting in a life-safety role, a shower valve, a backflow device, a T&P relief line, is treated as noncompliant until its listing can be verified, not assumed compliant because it looks similar to a listed product.
A worked example on shower sizing: a proposed shower stall measures 32 inches by 32 inches at its narrowest interior dimension, giving an interior area of 32 times 32, or 1,024 square inches. Both the 900-square-inch area minimum and the 30-inch dimension minimum are clearly met, so the standard rule applies without needing the 25-inch/1,300-square-inch alternative. If the same stall were instead 26 inches by 50 inches, the smaller dimension of 26 inches would fail the ordinary 30-inch minimum, but the area of 26 times 50, or 1,300 square inches, exactly meets the alternative threshold that permits a dimension as small as 25 inches, so this layout would pass under the alternative provision.
1. Under P2705.1, the minimum clearance in front of a water closet, to any wall, fixture, or door, is:
2. An inspector measures a water closet compartment and finds only 12 inches from the fixture's center to the side wall. This compartment:
3. Under P2708.1, a shower compartment's minimum interior cross-sectional area is:
4. An inspector finds a shower stall measuring 26 inches by 50 inches (1,300 square inches). Under P2708.1, this shower:
5. Under P2708.4, an individual shower valve or a tub-shower combination valve must be a type that:
6. An inspector finds an older two-handle shower valve reused behind newly retiled surround. The most likely code concern is:
7. Under P2708.4 and P2713.3, shower and bathtub valves must be limited to a maximum setting of:
8. An inspector finds a whirlpool bathtub installed with the deck fully tiled and no way to reach the circulation pump. Under P2720, this installation is:
9. Under Table P2903.2, the maximum flow rate for a showerhead is:
10. Under P2717.2, a dishwasher's discharge pipe or tubing must:
11. An inspector finds a newly installed dishwasher that will not drain, connected to a food waste disposer. A common cause in this situation is:
12. An inspector finds a shower valve on a rough-in with no legible listing mark of any kind. The correct approach is to:
13. Two water closets, lavatories, or bidets installed side by side must have their centerlines spaced at least:
14. A proposed shower stall measures 32 inches by 32 inches, for an interior area of 1,024 square inches. Under P2708.1, this shower: