This is one of the least understood parts of pressure washing, and one of the most important for anyone doing larger-scale or commercial cleaning in Indianapolis. Here's how the regulatory framework actually works.
Two Different Systems: Storm Sewer vs. Sanitary Sewer
Indianapolis, like most cities, has two separate underground systems: the sanitary sewer, which carries wastewater from sinks, toilets, and drains to a treatment plant, and the storm sewer, which carries rainwater runoff directly to local creeks and waterways with no treatment at all. Pressure washing wastewater is not supposed to go into either one without appropriate handling — into the storm sewer because it's untreated discharge into waterways, and into the sanitary sewer only with proper authorization.
The MS4 Permit Framework
Indianapolis operates under an MS4 (Municipal Separate Storm Sewer System) permit issued by IDEM, which requires the city to actively prevent illicit discharges into the storm sewer system — pressure washing wastewater containing detergent, oil, or other contaminants qualifies as exactly that kind of discharge if it enters a storm drain untreated.
What IDEM's Guidance Actually Says
The Indiana Department of Environmental Management's fact sheet on power washing is direct about this: discharging contaminated wastewater into Waters of the State without authorization is prohibited, and that includes discharge through storm sewers or other conveyances that ultimately reach a waterway. If wastewater needs to go somewhere like a sanitary sewer connection, written permission from the local POTW (publicly owned treatment works) is the proper channel — not just assuming it's fine.
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What This Looks Like on a Real Job
In practice, proper handling means containing or diverting wash water away from storm drains rather than letting it run freely downhill, using vacuum recovery on jobs where it's warranted, and being especially careful on any job involving degreasers, oil stains, or chemical cleaners rather than plain water. This applies at both residential and commercial scale, though larger commercial lots — see our guide on commercial power washing for storefronts and parking lots — generate enough runoff volume that it matters even more.
Why This Should Factor Into Who You Hire
A company that understands and follows these rules is protecting you, not just themselves — property owners can face liability for illicit discharges that originate on their property, even if a contractor caused them. It's a legitimate question to ask when choosing a pressure washing company, right alongside insurance and pricing.
How We Handle It
We follow proper wastewater practices on every job throughout Indianapolis and suburbs including Westfield, residential and commercial alike — it's part of doing the job right, not an optional add-on.
Sources: IDEM Power Washing Fact Sheet; Indianapolis-Marion County stormwater ordinance (MS4 program).