Where the wash water goes: storm drains and runoff in Wake County

Storm drains are not sewers

Two separate pipe systems run under most Wake County streets. Water that goes down a drain inside your house runs to a treatment plant, where it’s cleaned before release. Water that goes into a curb inlet or a grate in the street runs to a nearby creek or stream instead. Raleigh’s stormwater page puts it plainly, in its section on carpet-cleaning water headed for a storm drain: that water “is not treated” before it reaches a stream.

That difference is why the soap and dirt in wash water matters. A driveway or a section of siding that’s been cleaned with soap has runoff, and that runoff goes somewhere. If it reaches a storm drain, it reaches a creek carrying whatever was in the wash water.

What Raleigh asks of professionals who pressure wash pavement

Raleigh’s stormwater page tells professionals who pressure wash pavement not to use soaps or chemicals, and to sweep surfaces first. It also asks them to collect the wash water and dispose of it in a sink or drain that connects to the sewer system, not a storm drain. Where that isn’t possible, it says to use a drain seal, filter sock, or another method to filter the water or redirect it away from a drain.

Concrete is normally cleaned with plain water at high pressure (see soft washing versus pressure washing), so soap shouldn’t be needed on a driveway, and Raleigh asks professionals to collect the wash water either way.

The same page tells residents washing a car at home something different: wash in the yard or on gravel, and direct the wash water toward the lawn or a planted area.

Most of a pressure washing job’s runoff comes off the surface being cleaned. Siding rinse water runs down to the ground, and a roof soft wash sends its rinse off the eaves and gutters and onto the driveway or lawn below. Once it’s on the ground, it moves toward whatever’s lowest: a storm drain at the curb, or a ditch.

What Wake County counts as an illicit discharge

Wake County Watershed Management’s FAQ page defines an illicit discharge as a flow into a “stormwater conveyance” that isn’t stormwater runoff or an allowed discharge, and lists examples including oil, antifreeze, animal waste, chemicals, and septic tank discharge. The page doesn’t name wash water specifically, but its own advice is direct: “never dump anything down storm drains or in streams.”

Cary runs its own stormwater program. Check Cary’s stormwater page or call the town before assuming Raleigh’s or the county’s rules apply there.

Questions to ask a company about soap and runoff

A company that regularly washes driveways and siding in Raleigh or elsewhere in Wake County should already have a routine that matches what Raleigh’s page asks of professionals: skip the soap on pavement and collect the wash water. Worth asking directly:

• Where does the wash water go: collected and drained to a sewer connection, or left to run off into the yard or street?
• What do you use to keep water and soap away from a nearby storm drain or curb inlet?
• Do you carry a drain seal or filter sock for jobs near a storm drain?
• Do you sweep loose dirt and debris off pavement before you start?
• What’s in the cleaning solution, and is it labeled biodegradable?
• If my driveway slopes toward the street, how do you keep the runoff from reaching the curb?
• Have you worked a job near a storm drain before, and what did you do differently?

Our guide on what to ask before you hire covers insurance and written estimates; this list goes further into where the water itself ends up, which matters most on driveway and concrete jobs.

How to report a problem

If you see soapy water or discoloration running toward a storm drain, Raleigh’s Stormwater Helpline takes reports at 919-996-3940, or by email at IllegalDischarge@raleighnc.gov. In Wake County, Watershed Management’s Customer Service line is 919-856-7400. In other towns, call your town’s stormwater or public works office. Both numbers above are current as of September 25, 2026.

Have the address ready and describe what you see.