Can a floor sink be wet vented?

Because the wet vent rules are written around bathrooms. IPC Section 912.1 allows "any combination of fixtures within two bathroom groups located on the same floor level" to be vented by a horizontal wet vent, and it adds: "Only the fixtures within the bathroom groups shall connect to the wet-vented horizontal branch drain. Any additional fixtures shall discharge downstream of the horizontal wet vent."

A bathroom group, per the Chapter 2 definition, is a water closet, lavatory, bathtub or shower, "including or excluding a bidet, an emergency floor drain or both." The only drain on that list is an emergency floor drain, defined as "A floor drain that does not receive the discharge of any drain or indirect waste pipe." A floor sink in a kitchen, bar or mechanical room usually exists to catch indirect waste. The code's own definition of a waste receptor is "A floor sink, standpipe, hub drain or floor drain that receives the discharge of one or more indirect waste pipes." That puts it outside the bathroom group, so it cannot ride on a bathroom wet vent.

Two details make the picture clearer. A true emergency floor drain in a restroom can be part of a wet-vented bathroom group, but even then Section 912.2.1 says the dry vent connection must be an individual or common vent "for any bathroom group fixture, except an emergency floor drain." And the ICC Building Safety Journal's technical article describes a horizontal wet vent as a branch drain "increased in size larger than what is normally required," which leaves air space above the flow. That design is built around bathroom fixtures on one floor level, not a kitchen's floor sinks.

The code gives several routes, and the designer picks one that fits the building.

• Individual or common vent. A conventional vent pipe from the trap arm. Table 909.1 limits how far the trap can sit from its vent, so the layout decides how easy this is. See what a plumbing vent is for the basics.
• Circuit vent. Section 914.1 allows "not more than eight fixtures connected to a horizontal branch drain" to be circuit vented, and each fixture drain has to connect horizontally to the branch. This is common in rows of fixtures.
• Air admittance valve. Chapter 9 Section 918 allows vent systems using air admittance valves, with individual and branch-type valves conforming to ASSE 1051, installed to the manufacturer's instructions. Our page on air admittance valves covers what they are.
• Combination waste and vent. Section 915.1 says this type of system "shall not serve fixtures other than floor drains, sinks, lavatories and drinking fountains." It sets a size table, a slope cap of 4 percent, and limits the only vertical pipe to an 8 foot drop. A floor sink is closest to a floor drain or sink, but whether your plan reviewer will treat it as one is a local call, so ask before relying on it. The UPC has its own version, covered on our UPC combination waste and vent page.

No. Phoenix's published amendments to the 2024 IPC do not list Chapter 9. The list covers sections such as 403.2, 604.4, 605.25, 704.1, 803.1, the grease interceptor sections and 1106.1, so the model venting text applies for plans submitted under the IPC. Phoenix lets the designer choose the IPC or the Uniform Plumbing Code (UPC), both as amended, and the UPC has its own venting chapter with different names for the same ideas. If your drawings cite the UPC, the UPC rules govern the vent design, and the quoted IPC sections above do not.

A floor sink in a commercial kitchen often takes the drain of a prep sink, ice machine or steamer through an air gap or air break, which is how the code defines an indirect waste pipe. Its vent usually shows on the plumbing plans as its own line or a common vent for the group of kitchen fixtures. When a remodel moves the floor sink, the vent has to move with it, and the trap-to-vent distance is the number inspectors check first. A floor sink that gurgles, smells or loses its trap seal after a change is often a venting problem, not a clog. Floor sink versus floor drain versus mop sink shows how the three fixtures differ, and when a commercial kitchen needs a floor sink explains where the code asks for one.

HQ is licensed and insured and gives free estimates, so a plumber can look at a gurgling floor sink and tell you whether the cause is a vent, a trap or a drain.