A commercial kitchen needs an approved waste receptor where equipment must drain indirectly, often a floor sink. Food prep equipment needs an air gap; other connections may allow an air break. A floor sink must be trapped, vented and accessible. The adopted code and county-approved plans determine the layout.
Why does a kitchen need indirect drains at all?
To keep sewage out of food equipment. The code's own description of the chapter says "a backup of liquid waste in a drainage system could contaminate equipment and appliances," and that the chapter covers "the applications that require an indirect discharge connection to the building's drainage system."
The rule behind it is broad. Section 801.2 of the 2024 International Plumbing Code (IPC), which Phoenix adopted, says equipment that serves functions such as "cooling, or storage of ice or foods" and discharges to the drainage system "shall be provided with protection against backflow, flooding, fouling, contamination and stoppage of the drain." An indirect connection is how that protection works. The drain pipe ends in open air, above a separate trapped receptor, so there's no pipe path for waste to travel backward. Phoenix's amendments to the 2024 IPC don't change Section 802.
Our page on the difference between a floor sink, floor drain and mop sink explains how each receptor differs.
What equipment has to drain indirectly?
Section 802.1 lists it. In a commercial kitchen, "Food-handling equipment, in other than dwelling units, clear-water waste, humidifiers, dishwashing machines and utensils, pots, pans and dishwashing sinks shall discharge through an indirect waste pipe." In practice, that list covers:
| Equipment | Code section | Connection allowed |
|---|---|---|
| Food prep and storage equipment (prep sinks, steam tables, ice machines, food display cases) | 802.1.1 | Air gap |
| Floor drains in walk-in coolers and freezers | 802.1.2 | Air gap (air break or air gap if protected by a backwater valve) |
| Potable clear water, such as sterilizers and relief valves | 802.1.3 | Air gap |
| Nonpotable clear water, such as process tanks, filters and boilers | 802.1.5 | Air break or air gap |
| Commercial dishwashing machines | 802.1.6 | Air break or air gap |
| Sinks for washing utensils, dishes, pots and pans | 802.1.7 | Air break or air gap |
The section also sets the default for everything else. "Fixtures not required to be indirectly connected by this section" connect directly, following Chapter 7. Hand sinks and restroom fixtures, for example, connect directly.
### Food prep equipment needs an air gap
Section 802.1.1 is the strictest. It says equipment "utilized for the storage, preparation and handling of food shall discharge through an indirect waste pipe by means of an air gap." It adds that "Each well of a multiple-compartment sink shall discharge independently to a waste receptor." So a two-well prep sink needs two drain lines ending over the receptor, not one combined tailpiece.
### Walk-in coolers have their own rule
A floor drain inside a walk-in is still an indirect waste. Section 802.1.2 says those drains "shall be indirectly connected to the sanitary drainage system by means of an air gap." In a freezer, the line "shall not be trapped and shall indirectly discharge into a waste receptor located outside of the area subject to freezing." That's why you often see a floor sink just outside the walk-in door.
What's the difference between an air gap and an air break?
Both leave open air between the drain pipe and the receptor. The difference is how much.
- Air gap. The pipe ends above the receptor's rim. Section 802.3.1 says the gap "shall be not less than twice the effective opening of the indirect waste pipe." A 1-inch drain line needs at least 2 inches of open air above the flood level rim.
- Air break. The pipe can extend down into the receptor, below its rim, as long as it stays above the water. Section 802.3.2 says the air break goes "between the indirect waste pipe and the trap seal of the waste receptor."
An air gap gives more protection, which is why the code requires it for food prep. An air break is allowed for dishwashers and pot sinks under the IPC. But the health department can ask for more, covered below. Our page on what a dishwasher air gap is shows the residential version of the same idea.
What does Maricopa County require?
The county's health plan review adds its own rules on top of the plumbing code. For restaurants and other open food service, its Minimum Requirements for Food Establishments say:
- "The 3-compartment sink drain line must be indirectly plumbed with a minimum 1-inch air gap where permissible."
- A separate food prep sink must be "indirectly plumbed with an approved minimum 1-inch air gap off the drain line."
- "Garbage disposals are not permitted on food preparation sinks, 1-compartment, 2-compartment, or 3-compartment sinks."
Note the difference: the IPC allows an air break at a pot sink, but the county asks for a 1-inch air gap "where permissible." Design to the stricter rule and your plans are less likely to come back with corrections. Our guide to Maricopa County restaurant plan review covers the rest of the county checklist, and our page on restaurant plumbing health inspection requirements covers what the inspector checks.
What makes a floor sink compliant?
The receptor has rules too, in Section 802.4 and the sections around it.
- It must be trapped and vented. Section 802.2 says "Waste receptors shall be trapped and vented and shall connect to the building drainage system."
- It needs a strainer or basket. "A removable strainer or basket shall cover the outlet of waste receptors," except for clear-water hub drains and standpipes.
- It can't be hidden. Receptors "shall not be installed in concealed spaces," and "Ready access shall be provided to waste receptors." A floor sink under a cabinet with no access panel fails.
- It must be big enough. Section 802.4.1 says a receptor "shall be sized for the maximum discharge of all indirect waste pipes served by the receptor," and installed "to prevent splashing or flooding."
- Long indirect lines need a trap. An indirect waste pipe "that exceeds 30 inches (762 mm) in developed length measured horizontally, or 54 inches (1372 mm) in total developed length, shall be trapped."
In a restaurant, floor sinks often connect to the grease interceptor line, so they're also where grease backups show up first. Our guide to a grease trap backing up into floor sinks explains what that means.
### How many floor sinks does a kitchen need?
The code doesn't set a count. It sets rules for each drain. The number comes from the equipment layout: every indirect drain has to reach a receptor with a proper gap, and each receptor has to be big enough for what drains into it. A kitchen with equipment on two walls may need several floor sinks. A small cafe may need one or two. Your plumbing plans and the county review settle the final number.
### When should you plan floor sinks?
Before the slab is cut. Floor sinks sit in the floor and tie into the drain system below, so moving one later means saw-cutting concrete. Lay out the equipment first, then place floor sinks where the drain lines can reach them with the right gap. A few habits help:
- Keep receptors out from under equipment that has to be pulled for cleaning.
- Leave room above each floor sink to see the gap and clean the strainer.
- Check that an ice machine's drain line has its own gap, not a hose pushed into the sink below the rim.
If you're converting a space, our guides to commercial tenant improvement plumbing and changing a retail space to a restaurant in Phoenix cover the permit side, and our page on an ice machine backflow preventer covers the supply side.
HQ Plumbing & Air lays out and installs floor sinks, indirect waste lines and grease interceptor connections for restaurants across the Phoenix area. We're licensed and insured, available 24/7 for backups, and every project starts with a free estimate and upfront pricing. See our commercial plumbing services.
Every indirect drain needs a place to land. In most kitchens, that place is a floor sink.