Where can car wash and detailing wastewater drain?

Because the storm drain is not a treatment system. Phoenix Water Services says "The storm drain sewer takes all the stormwater runoff and goes untreated to rivers, washes and retention basins." Soap, oil, brake dust and sediment go with it.

The rule is layered:

• Federal. EPA's stormwater rules (40 CFR 122.26(b)(2)) define an illicit discharge as "any discharge to a municipal separate storm sewer that is not composed entirely of storm water," with narrow exceptions. Cities that run a small storm sewer system must, under 40 CFR 122.34, "effectively prohibit, through ordinance, or other regulatory mechanism, non-storm water discharges into the storm sewer system."
• State. ADEQ's car wash guide says "Substances dumped directly into storm drains can impair water quality and lead to Clean Water Act violations," and tells owners it is "crucial to avoid hosing down the lot or property into streets or storm drains."
• Phoenix. City Code 32C-103 says a person may not release "any substance that is not composed entirely of stormwater" to a public right-of-way, retention basin or storm drain system. The list of exceptions includes "Individual residential car washing," when it is not a significant source of pollutants and does not create a nuisance. It also bars a direct connection to the public storm drain without the City Manager's written permission.
• Chandler. Section 45-6 prohibits discharging anything that is not stormwater to rights-of-way or the stormwater collection system. Its exception covers "non-commercial car washes where only vehicle exteriors are washed with water and biodegradable soaps," unless significant materials or sediment reach the city system.
• Maricopa County (unincorporated urbanized areas). The county regulation bars introducing "any pollutants or waters containing any pollutants, other than Stormwater" into its storm drain system. It treats a conveyance that lets "sewage, process wastewater, and wash water" reach the storm system as an illicit connection, even if it was approved before. It applies to the county's own system in the urbanized areas.

If you see dumping, Phoenix's stormwater hotline is 602-256-3190, staffed 24 hours a day.

To the sanitary sewer, or into a closed loop. EPA notes that commercial car washes "often recycle their water or must treat their wash water before release into the sanitary sewer system." Pretreatment usually means a sand and oil interceptor. Our sand and oil interceptor page covers the code, sizing and city add-ons, and the car wash reuse page covers recycling and ADEQ's general permit for wash water you discharge on site.

Three points keep wash-bay plumbing out of trouble:

1. 1Drains go to the sanitary side. The wash bay floor drain connects to the interceptor and then to the sewer, not to a yard drain or curb outlet.
2. 2Keep rain out of the sanitary sewer. Phoenix's sewer code bars "any stormwater, surface water, groundwater, roof runoff, surface drainage, or unpolluted water that constitutes inflow" unless the Director approves otherwise. An open wash pad that collects rain needs a plan for that, usually a roof or a diverter.
3. 3Interceptor contents are waste, not drain water. Phoenix says the removed contents "may not be reintroduced or decanted back into the interceptor, a sewer cleanout, another interceptor, or other non-allowed opening of a collection system or private sewer system." ADEQ says sludge is the most common hazardous waste at a car wash and to use only licensed businesses to transport and dispose of it. That is a hauler's job, not a plumber's.

The residential exception is narrow. Phoenix excepts "Individual residential car washing," meaning someone washing their own vehicle. A person who washes vehicles for a fee on someone's driveway is not that. Phoenix's stormwater code requires a written stormwater management plan from a person who "conducts an activity for a fee or charge on residential property" that has reasonable potential to affect stormwater quality, and the plan must be provided to the city on request. It lists the significant materials on site and how they are used, stored, treated or disposed of.

Practical options, from EPA's tips for people washing vehicles: use biodegradable, phosphate-free detergent and limit how much you use, direct wash water to pervious areas like grass or gravel where allowed, or use car wash kits that protect nearby storm drains. Whether a mobile operator may capture and discharge to a sanitary sewer cleanout is a question for the local wastewater utility. Ask first and get it in writing.

Walk the lot and trace every drain. If a wash bay, vacuum area or detailing pad drains anywhere you cannot trace to the sanitary sewer, assume it may be a storm connection. A licensed plumber can smoke- or dye-test the lines and camera the pipe. HQ is licensed and insured, and gives free estimates with upfront pricing. We handle the plumbing: drains, interceptor connections and backflow protection on the supply.