Can You Pressure Wash Into Storm Drains in California?

Why pressure washing water cannot go into a storm drain

Storm drains are built to carry rain, and in Southern California they discharge to creeks, rivers and the ocean without treatment. The federal Clean Water Act requires municipal separate storm sewer system (MS4) permits to effectively prohibit non-stormwater discharges, and California's regional water boards write that prohibition into the permits they issue to cities and counties. Cities enforce it through their own codes; the City of San Diego, for example, prohibits polluted wash water from pressure washing in Municipal Code section 43.0304.

Several regional boards cover Southern California: Los Angeles, Santa Ana, San Diego, Colorado River Basin (which includes the Coachella Valley) and Lahontan (which includes the High Desert). Local details and exemptions differ, but the starting point everywhere is the same: wash water from commercial surfaces stays out of the storm drain.

What makes wash water a pollutant

The problem is not the water but what it carries. Even without soap, pressure washing strips oil, metals, food waste and sediment from hard surfaces and moves them along with the runoff.

How contractors keep wash water out of storm drains

Good practice follows a sequence: remove whatever can be removed dry, protect the drains, wash with as little water and chemistry as the job needs, then recover everything.

• Sweep, pick up litter and scrape gum before any water is used
• Treat oil and grease spots with absorbent and dispose of it properly
• Cover or seal nearby storm drain inlets with drain mats or plugs
• Use berms or booms to pool water where it can be collected
• Recover water with a vacuum system or a surface cleaner that has recovery
• Use high-pressure, low-volume equipment and minimal detergent, preferably biodegradable and phosphate-free
• Never use acids or solvents where runoff could reach the gutter
• Avoid washing ahead of forecast rain, which can carry leftover residue into drains

Where recovered wash water can go

Recovered water still needs a lawful destination. The usual one is the sanitary sewer, but only with permission from the local wastewater agency, which may set conditions such as filtering out solids, passing the water through a grease interceptor or discharging only at an approved cleanout or sink. Some agencies require a permit for regular discharges.

Some local codes allow small amounts of plain water to soak into landscaping on the property, provided nothing flows off-site. Water that cannot go to the sewer or landscaping can be taken away by a licensed liquid waste hauler. Debris, gum and used absorbent go in the trash, never down a drain.

What to require from a pressure washing contractor

Local ordinances can hold property owners responsible for discharges from their sites, so the contract should make the contractor's duties explicit.

• A written plan for each site covering drain protection, recovery method and disposal point
• The equipment that will be on site, including inlet covers and recovery units
• Product names and safety data sheets for any detergents
• Where recovered water is discharged and who approved it
• Before-and-after photos, including the protected inlets
• Responsibility for any fine or cleanup cost caused by the contractor's discharge

How EBS plans pressure washing

Pressure washing is part of EBS's specialized capacity, alongside floor care, carpet, glass and project work. At the walkthrough, the scope for each site records the surfaces, frequency and timing (often overnight or on weekends, when entries and parking areas are empty) together with how drains will be protected and where wash water will go. Supervisors check the work and document completion, and the property has a single point of contact for any concern.