Storm Sewer VS Sanitary Sewer

Storm Sewer vs. Sanitary Sewer

Two drainage systems serve all development.  Each system has a different purpose and does different things.

The storm sewer system controls rainfall and other natural run-off to protect downstream owners.  In undeveloped areas, rainwater seeps through the ground into the water table.  Development of a parcel places structures or pavement over the existing dirt, preventing the transfer of rainwater into the water table.  Storm sewer collects rainfall and other drainage from developed areas and transports it to holding ponds, where the water can gradually enter our streams and other natural bodies of water. This prevents erosion and degradation of our stream valleys downstream from the development. Storm drain inlets are typically found in curbs and low-lying outdoor areas.  In most planned developments, the County requires that the developer install as a part of its initial development a storm sewer management system adequate to serve the whole development when it is fully built out.  The storm sewer system is not intended to handle effluent or other contaminated water.  That is the function of the sanitary sewer system.


The sanitary sewer system controls wastewater.  The sanitary sewer collects discharge from our bathrooms, kitchens, sinks and other plumbing fixtures and transports the discharge to waste water treatment facilities where it is filtered, treated and, once clean, released back into the environment. The sanitary sewer system is not intended to manage rainwater or other normal runoff.  That is the function of the storm sewer system. Soapy water from the carwash is discharged into the sanitary sewer system, not the storm sewer system. 

Example of permeable pavers

When Festival Lakes was developed, the County required and the developer provided storm water management systems sufficient to handle all storm water runoff from the shopping center as if it had been fully built out.   The pad site where White Horse proposes to build the carwash was originally planned for a 6,200 square foot building.  The storm water management system at Festival Lakes is built to handle all the run-off from a building of that size. Thus, the existing storm water management system is more than sufficient for the proposed 4,800 square foot carwash building.  In addition to its smaller footprint, the carwash further decreases the amount of runoff from the site by including permeable pavers, which allow rainfall to absorb back into the soil. For further information on permeable pavers, and how they work, click here! Finally, White Horse has committed to collect rainfall from its roof for reuse in the carwash. This further decreases the volume of storm sewer runoff from the site.   The storm water management system already constructed at Festival Lakes is more than adequate to manage storm water run-off from the carwash facility.

The operation of the carwash facility does not impact the storm water management system at Festival Lakes.  The water which White Horse uses to wash cars is recycled and reclaimed through the use of efficient and environmentally friendly reclamation equipment.  What little water is lost represents the water left on the washed car which is wiped down before the car leaves the carwash site.  The reclamation system is not attached to the storm water management system.  The overflow water from the carwash reclamation tanks flows to the sanitary sewer, not the storm sewer and thus does not impact the existing storm water capacity

Professional Carwashes are Safer for the Environment than Home Washing

Did you know that professional carwashes are actually much better for the environment than home washing? Its true! We use low flow nozzles and computers that tell us when exactly to use water in our carwash process. In fact, Fairfax County, along with many other municipalities, actually encourages washing your car at a professional carwash as it requires them to adhere to wastewater discharge and plumbing requirements. But don’t take our word for it, read about it on Fairfax County’s website!