Yes. A commercial laundry needs a lint interceptor under 2024 IPC Section 1003.6. Washers must drain through an interceptor with a removable wire basket that stops solids half an inch or larger. Only washers in a dwelling unit, and a single home-style washer elsewhere, are exempt. Phoenix also lists laundries for pretreatment.
What the plumbing code says about washer drains
The 2024 International Plumbing Code (IPC) is the base code in Phoenix, Mesa, Chandler and Tempe. Phoenix also adopted the 2024 Uniform Plumbing Code, and Scottsdale uses the 2021 IPC. The rule sits in Chapter 10.
IPC Section 1003.6 is titled Clothes washer discharge interceptor. It says "Clothes washers shall discharge through an interceptor that is provided with a wire basket or similar device, removable for cleaning, that prevents passage into the drainage system of solids 1/2 inch (12.7 mm) or larger in size, string, rags, buttons or other materials detrimental to the public sewage system."
Three details in that sentence matter on a real job:
- The basket. A wire basket or similar device has to be there. A strainer glued in place doesn't count, because it has to be removable for cleaning.
- The half-inch rule. The device has to stop solids half an inch or larger. That is a performance rule. The code doesn't set a mesh size beyond it.
- More than solids. String, rags and buttons are named too.
### Who is exempt
The exceptions in IPC 1003.6 are short. First, "Clothes washers in individual dwelling units shall not be required to discharge through an interceptor." That's the washer in a house or an apartment unit.
Second, "A single clothes washer designed for use in individual dwelling units and installed in a location other than an individual dwelling unit shall not be required to discharge through an interceptor." Picture one home-style washer in a fire station, a small salon or an office break room.
Look closely at the word single. Two home-style washers in a shared apartment laundry room don't fit the second exception. Neither does any commercial machine. So a building owner can go from no interceptor to a required one by adding a second washer.
| Setup | Interceptor under IPC 1003.6? |
|---|---|
| Washer inside a house or apartment unit | Not required |
| One home-style washer in a business | Not required |
| Two or more home-style washers in a shared laundry room | Required |
| Laundromat or self-service laundry | Required |
| Hotel, gym or care home laundry with commercial or multiple washers | Required |
| Commercial or industrial laundry | Required |
### Venting and access
Two general rules apply to lint interceptors like any other. IPC 1003.9 says interceptors "shall be designed so as not to become air bound," and must be vented under one of the Chapter 9 methods. The access rule right after it says interceptors must be reachable for service and kept up "by periodic removal of accumulated grease, scum, oil, or other floating substances and solids deposited in the interceptor or separator."
Mesa's plumbing plan review checklist puts both into one line: "Grease or sand oil or lint interceptors shall be installed and vented properly." Plans that skip the lint interceptor or its vent can come back with review comments.
What Valley cities add
The plumbing code decides that you need a device. The city decides which device, how often it's cleaned, and what you keep on file.
Phoenix. The city's due diligence guide lists laundries first among businesses where "Wastewater pretreatment devices (such as interceptors for grease, oil, & sand) are required." City Code 28-12 says interceptors must be installed and operated by laundries "when the Director determines they are necessary" for liquid wastes with grease, oil, solids or other harmful ingredients. Under 28-13, the interceptor must be of "a type and capacity approved by the Director," and must be readily and easily accessible for cleaning and inspection.
The cleaning rules in Section 28-15 name lint directly. The owner must periodically remove "all accumulated grease, lint, oil, sand, sludge, solids, wastewater, and other materials." Under Section 28-15, a gravity interceptor must be pumped and cleaned before the combined lint, sludge and solids exceed 25 percent of its liquid volume, and at least every 12 months unless the Director grants a variance. A hydromechanical interceptor has a 30-day minimum cycle, and none may go more than 90 days without maintenance. Records of each cleaning, the volume removed and where it went must stay on site for at least three years.
Phoenix's sewer billing also treats laundries as their own class. Section 28-35 figures a self-service laundry's sewer volume from eighty-five percent of each month's water meter reading, times a stabilization factor, rather than the winter average used for most commercial accounts. The rate table in Section 28-39 lists a separate "Laundries/Commercial" category.
Tempe. City Code 27-22 lets the Public Works Director set rules, approved by the City Council, that require nondomestic users to install, clean, maintain, repair and allow inspection of pretreatment devices where wastewater contains "excessive amounts of lint, sand, fog, or other pollutants." The type and capacity follow those rules.
Phoenix also inspects. Its Commercial Inspection Program says staff "educate and inspect Commercial Users to ensure compliance with Phoenix City Code Chapter 28 (Sewers)," and the facilities it lists include hotels and laundries. Section 28-17 gives a city representative free access at all reasonable hours to commercial premises tied to the sewer, to check compliance. So the basket, the interceptor and the cleaning records should all be ready to show on any business day.
Other Valley cities write their own sewer rules too. Check with the city that serves the building before you order equipment.
Scenarios, sizing and next steps
Opening a laundromat in a strip center. The washers need a lint interceptor, approved by the city, sized for the number of machines and their drain rate. The drain line from the washers is often a trench or a large common line, and the interceptor sits where a pumper can reach it. For how a shared building handles plumbing changes, see commercial tenant improvement plumbing.
Adding a laundry room to an apartment complex. One home-style washer in a leasing office may be exempt. A room of shared machines is not.
A hotel or care home replacing machines. New washers with a higher discharge rate can outgrow the old interceptor. Check the rating before the swap.
A laundry that keeps backing up. A full basket or a lint-choked line is the usual suspect. Cleaning the basket is the owner's routine job. A licensed liquid waste hauler pumps and disposes of the interceptor's contents. If the line past the interceptor is matted with lint, hydro jetting clears it; see why the same drain keeps clogging.
Here's the order that saves the most rework:
- 1Count and list the machines. Note which are commercial and which are home-style.
- 2Get the discharge rates. The washer maker's data sheet gives the drain rate for each machine.
- 3Call the city's pretreatment staff. In Phoenix, ask which interceptor types are approved for laundries.
- 4Show the interceptor and its vent on the plans. Include access for cleaning.
- 5Set the cleaning schedule. Put baskets on a routine and book a licensed hauler, then keep three years of records.
Laundries share a lot with other pretreatment uses. The venting rules in grease interceptor venting requirements apply to lint interceptors too, and the quarter-full rule covers the fill limit behind Phoenix's cleaning rule.
HQ Plumbing & Air installs and repairs lint interceptors, washer drain piping and vents for Valley businesses, and clears laundry lines with drain cleaning and hydro jetting, with free estimates and upfront pricing.