Sanitary Sewer Overflows

FOG stands for Fats, Oils and Grease, all of which can severely damage your sanitary sewer system. FOG includes animal and vegetable fats, as well as oils used to cook and prepare food. When poured down the drain, FOG can cause problems in sanitary sewer pipes and sewer laterals. Grease buildup in pipes can cause major damage to pipes and lead to sewage back-ups in your business

A sanitary sewer overflow (SSO) is an overflow of untreated or partially treated sewage from a sanitary sewer system. 

Most sewer systems experience occasional SSOs. Some SSO causes are:

• Inappropriate materials placed into sewers, such as fats, oils and grease (FOG) and some household products such as baby and facial wipes, sanitary pads and tampons. All of these can create blockages.
• Tree roots and/or excessive stormwater or groundwater entering sewer lines through defects or cracks.
• Inappropriate connections such as sump pumps, roof gutters and downspouts, foundation drains and area drains.
• Power loss.
• Equipment failures and breaks.
• Intentional acts of vandalism.
• Heavy rainfall and natural disasters. 

To prevent clogs and SSOs, never pour fats, oils, or grease (FOG) down drains. Dispose of them in sealed containers. Despite being labeled "flushable," wipes can cause clogs and should not be flushed. Ensure storm water connections are correct and report suspected issues. Keep sewer cleanout caps secured for line access. 

Unfortunately, overflows cannot be prevented entirely. The EPA indicates that “a few SSOs may be unavoidable. Unavoidable SSOs include those occurring from unpreventable vandalism, some types of blockages, extreme rainstorms, and acts of nature such as earthquakes or floods.” 

Prince William Water has invested in sewer improvements to prevent SSOs, including cleaning and maintaining the system:

• Rehabilitating and replacing broken or leaking lines to reduce storm water and groundwater infiltration into the sanitary sewer.  
• Upgrading or expanding sewer lines and pump stations.  
• Increasing sewage treatment capacity and improving plant dependability.  
• Removing fat, oil and grease (FOG) buildup from sewer systems.  
• Educating the public on how household goods like FOG and wipes can block sewer pipes. 

For reportable SSOs, Prince William Water posts on its website, Facebook and X. Signs in English and Spanish are placed at SSO sites, warning of potential illness for at least seven days. 

Any SSO that enters state waters or may reasonably be expected to enter state waters is reportable. Signage is placed at the site of the incident for seven days for reportable SSOs. Prince William Water also posts information about any active SSOs on our website and social media accounts. VDEQ maintains a Pollution Response Program (PREP) database, which is accessible to the public. This database shows all open SSO cases throughout the state, as well as a five-year period of record for closed SSO cases. 

SSOs discharge water and other contents from the sanitary sewage system. Avoid contact and report them to the Prince William Water Emergency Dispatch line at (703) 335-7990.

More information on the extent of environmental and human health impacts caused by SSOs can be found in the EPA report Impacts and Control of CSOs and SSOs.