Yes, if the room can take a new drain and vent. Under the 2024 International Plumbing Code, a laundry sink has its own trap and vent, or its waste line can tie into the washer's standpipe. In Phoenix, adding a fixture needs a plumbing permit. The drain location decides how hard the job is.
Do you need a permit to add a laundry sink?
In Phoenix, yes. The city's permit exemptions for plumbing cover stopping leaks, clearing stoppages, and replacing valves or fixtures with new ones, and they specify that a permit is required to relocate any valves, pipes or fixtures. They also exclude repairs that require the replacement or rearrangement of valves, pipes or fixtures. A laundry sink where none existed is a new fixture with a new drain and vent, so it is outside the exemptions. Our page on whether you need a permit to remodel a bathroom in Phoenix explains how the city draws that line.
Swapping an existing utility sink for a new one on the same trap and supply lines is the like-for-like case. A brand new sink is not.
Where can a laundry sink drain?
The IPC gives three workable layouts.
### Option 1: its own trap and vent
Each plumbing fixture must be separately trapped, per Section 1002.1, and the trap has to be vented. Section 901.2 says the vent system must keep the seal of any fixture trap from a pressure difference of more than 1 inch of water column, and Section 901.2.1 says traps and trapped fixtures must be vented by one of the methods in Chapter 9. Chapter 10 also sets trap placement limits: the vertical distance from the fixture outlet to the trap weir may not exceed 24 inches, and the horizontal distance from the fixture outlet to the trap inlet may not exceed 30 inches.
The size numbers come from the IPC's fixture tables. A laundry tray, with one or two compartments, is rated at 2 drainage fixture units with a minimum 1.5-inch trap, and each compartment must have a waste outlet not less than 1.5 inches in diameter. Vent pipes must be not less than 1.25 inches in diameter, and the vent must be at least half the diameter of the drain it serves.
### Option 2: tie the sink's waste into the washer standpipe
The IPC allows a shortcut. Section 802.4.3.1 says that as an alternative to a laundry tray connecting directly to the drainage system, a laundry tray waste line without a fixture trap can connect to a standpipe for an automatic clothes washer drain. Three limits apply:
- The standpipe must extend at least 30 inches above the weir of the standpipe trap.
- The standpipe must extend above the flood level rim of the laundry tray.
- The outlet of the laundry tray may not be more than 30 inches horizontally from the side of the standpipe.
This saves a second trap, but the laundry sink has to sit close to the washer box, and the standpipe has to be tall enough.
### Option 3: the washer drains into the laundry sink
Section 406.2 also permits the waste from an automatic clothes washer to discharge through an air break into a laundry sink instead of a standpipe. That is a common arrangement, with the washer hose hung over the sink.
### What else does the code say about the sink and the washer?
Section 418.1 says laundry trays must conform to the listed ASME or CSA product standards, so buy a sink sold as a laundry tray, and Section 418.2 requires each compartment to have a strainer or crossbar that restricts the clear opening of the waste outlet. On the washer side, Section 406.1 says the water supply to an automatic clothes washer must be protected against backflow, either by an air gap built into the machine or by a backflow preventer installed under Section 608. Section 406.2 adds that washers that discharge by gravity may drain to a waste receptor or an approved trench drain.
What are the rules for the washer standpipe?
If your plan uses a standpipe, the code sets these limits:
| Item | Requirement | Section |
|---|---|---|
| Standpipe trap and fixture drain | Not less than 2 inches in diameter | 406.2 |
| Connects to | A 3-inch or larger fixture branch or stack | 406.2 |
| Standpipe height above the trap weir | Not less than 18 inches and not more than 42 inches | 802.4.3 |
| Trapping | Individually trapped, with access for rodding | 802.4.3 |
| Laundry tray tied in | At least 30 inches above the weir, and above the tray's flood rim | 802.4.3.1 |
The 3-inch requirement matters in a remodel. An existing 2-inch line that served a washer may not meet today's connection rule, and a plumber will check what the branch behind the wall actually is.
Washer manufacturers add their own drain rules on top of the code, so check the installation guide for your washer and follow whichever number is stricter.
### What if the sink sits below the drain?
A sink in a basement or a low corner may be below the level where the drain can flow by gravity. Section 712.1 says building subdrains that cannot discharge to the sewer by gravity must discharge into a tightly covered and vented sump, lifted by automatic pumping equipment or another approved method. Section 712.2 requires a check valve and a full-open valve on the discharge side. Pumped sink systems have to follow those rules too, so do not treat a pump as an unregulated shortcut. Ask a plumber whether your location can drain by gravity before you pick a spot.
### How should you plan the job?
Work through these questions first. They decide the plan and the permit application.
- 1Where is the nearest vented drain? A sink close to an existing drain and vent is simpler than one that needs new runs.
- 2Where does the washer drain now? If a standpipe is there, option 2 may work.
- 3How far is the sink from the drain? The 24-inch and 30-inch trap limits shape the layout.
- 4Is the floor in the way? A new drain under a concrete slab means opening the slab, so the location of the drain matters.
- 5What does your city say? Ask for the adopted edition and any amendments.
If your washer already leaks at the wall, our page on why a washing machine leaks helps you tell a hose problem from a drain problem before you plan the remodel.
When should you call a plumber?
Call when the wall needs to be opened, the drain has to move, or you need a permit. A plumber can confirm the vent path, size the branch, pull the permit, and schedule the inspection. Our page on the Phoenix permit rules for replacing a water heater gives another example of how the city treats plumbing work. HQ Plumbing and Air is licensed and insured, takes emergency calls 24/7, and gives free estimates with an upfront price before work starts. See our plumbing services.