Not all pipelines are created equal—and when it comes to inspecting underground infrastructure, the differences between stormwater and sanitary sewer systems are significant. While both are essential for public health, safety, and environmental protection, the way each is managed, maintained, and inspected can vary drastically.
For municipalities looking to improve efficiency and make smarter decisions, understanding these distinctions is crucial. Here’s a deep dive into how storm and sanitary sewer systems differ—and why those differences matter.
1. Pipe Location and Access: The Hidden Complexity
Sanitary pipes are typically located in predictable, linear paths under streets or alleys. Access is usually through manholes located in the roadway, making it relatively easy for crews to plan inspections and navigate the system.
Storm pipes, on the other hand, are often routed through parks, open fields, ditches, or remote easements as they follow natural water flow toward outfalls like rivers, creeks, or detention ponds. In many cases, access points may not even be paved or visible, requiring additional equipment or effort to locate and reach them.
Operational Impact: Stormwater systems are designed to move runoff to receiving waters as efficiently as possible which often means more varied and remote routing.
2. Pipe Length, Size, and Configuration
Sanitary sewer mains generally consist of long, consistent runs. The system is designed to transport steady flows of wastewater from homes and businesses to treatment plants, and as such, pipe segments are engineered for uniformity.
Storm systems are more fragmented. Catch basin leads (short pipe segments from the street inlet to the main) are common and must be inspected separately. Mainline pipes can vary in length and size dramatically even within a single block.
Operational Impact: Storm inspections can involve larger cameras and more varied workflows. Sanitary inspections tend to be more standardized, while storm requires flexibility.
3. Flow Conditions and Timing Challenges
Sanitary lines carry a relatively constant flow of wastewater, which makes inspection scheduling more predictable. While they can contain hazardous gases and require careful ventilation, the flow itself is consistent and manageable.
Storm lines can be completely dry one day and full the next, depending on weather. Seasonal conditions like snowmelt, rainstorms, or even clogged grates can significantly impact whether a pipe can be inspected.
For example, a city like Portland, Maine, with 45+ inches of annual rain, may find its storm system flooded during peak inspection season unless proactive planning is in place.
Operational Impact: Stormwater inspection crews must closely monitor weather patterns and prioritize dry conditions. Sanitary inspection can generally proceed on a more consistent schedule.
4. Debris and Defect Types
Storm pipes are collectors of whatever the rain washes off the streets: leaves, sticks, sand, trash, road grit, and even animals. Debris accumulation is common and can quickly block flow if not addressed. Storm pipes are also more susceptible to root intrusion and sediment buildup.
Sanitary sewers face different challenges: fats, oils, and grease (FOG) from homes and restaurants can clog pipes and reduce capacity. Blockages are more likely to lead to backups into buildings or manholes resulting in major health risks and regulatory violations.
Both systems can suffer from cracks, joint separations, and collapses, but the causes and consequences differ.
Operational Impact: Storm inspections often involve clearing large debris and managing sediment. Sanitary inspections require awareness of buildup, corrosion, and chemical hazards..
5. Health and Safety Considerations
Sanitary systems always contain raw wastewater, so PPE (personal protective equipment), air quality monitoring, and confined space entry protocols are critical. Crews must be trained in handling biohazards and gas exposure.
Storm systems, while generally less toxic, may contain wildlife ranging from snakes and rodents to raccoons and even alligators in southern regions. Larger pipe diameters can also present fall risks.
Operational Impact: Both systems demand safety protocols, but the specific hazards differ. Agencies must train crews for both environments.
6. Inspection Productivity and Expectations
Storm inspections typically yield lower daily footage output due to variable access, debris removal, and shorter pipe runs. Catch basin leads, access challenges, and changing conditions reduce inspection speed.
Sanitary inspections are more streamlined, often completing longer sections in a single setup, which improves efficiency.
Operational Impact: Budgeting, staffing, and production goals must reflect these workflow realities. Comparing storm vs. sanitary output directly is a mistake—each requires its own metrics.
Why It Matters
For agencies investing in asset management and infrastructure renewal, it’s not enough to inspect both systems the same way. Storm and sanitary sewers demand different strategies, tools, and timelines.
Understanding the key differences leads to:
- More accurate inspection scheduling
- Better equipment planning
- Safer field operations
- Smarter budgeting and resource allocation
- Stronger justification for funding and rate increases
As cities across the country shift from reactive to proactive maintenance, recognizing these inspection nuances is the first step toward smarter infrastructure management.
