What’s Flowing Where: Stormwater vs. Sanitary Sewer Systems

Published on March 19, 2025

Florida has two distinct sewer systems: sanitary and stormwater. In Dunedin, these systems operate independently. Stormwater systems channel untreated rainwater runoff into natural waterways like Curlew Creek, Cedar Creek, and Jerry Branch. These natural waterways are known as surface waters, which include creeks, rivers, lakes, and other bodies of water found on the Earth’s surface. Meanwhile, sanitary sewer systems transport wastewater from homes and businesses through a separate network of pipes to a wastewater treatment plant.

Stormwater Sewer Systems

A stormwater system is designed to collect and manage runoff from rainwater. There are various types of stormwater systems to help manage that runoff. The most well-known stormwater systems include detention systems, retention systems, and swales.

Key Parts of Stormwater Sewer Systems

Detention systems, or detention ponds, are the most recognizable form of stormwater management. Stormwater flows into these ponds through pipes, where pollutants are filtered out. The stormwater then drains from the pond through a different pipe, or “outflow” structure. This system allows for treatment before discharging to surface waters.

Retention systems temporarily hold rainwater and allow it to slowly filter through the ground, instead of discharging directly to surface waters.

Swales, like ditches, are natural or man-made areas shaped to help rainwater soak into the ground or flow toward nearby water bodies. Most of the time, they’re dry, but after a storm, they can temporarily hold water until it slowly absorbs into the ground.

Depiction of how stormwater and sanitary sewer systems operate in the City of Dunedin.

Sanitary Sewer Systems

Sanitary sewer systems consist of pipes, or “laterals,” that are connected to homes, businesses, and other buildings. These pipes feed into main sewer lines that transport wastewater to treatment plants. The wastewater is then treated and supplied as reclaimed water for irrigation—but it isn’t safe to drink.

Key Parts of Sanitary Sewer Systems

Sanitary sewer systems have several key parts that make them different from stormwater systems. One important part is lift stations, which help push wastewater through the pipes in areas where gravity isn’t enough to keep things flowing. A common misunderstanding is that lift stations also carry stormwater—but they don’t. Lift stations are only used for wastewater. The City of Dunedin operates 47 lift stations.

Another key part is manhole covers, which provide access points so crews can perform maintenance. Unlike stormwater systems, sanitary systems don’t have open drains or grates.

Finally, all sewage collected in the sanitary system is sent to a wastewater treatment plant, where it’s treated before being released or reused as reclaimed water for irrigation. In contrast, stormwater usually flows untreated into nearby creeks and waterways.

Want to learn more about how Dunedin’s sanitary and stormwater sewer systems work? Check out the links below:

Wastewater Department: dunedingov.com/City-Services/Water-Utilities/Wastewater
Stormwater Division: dunedingov.com/City-Services/Water-Utilities/Stormwater