A sanitary sewer overflow is not a maintenance inconvenience — it is raw or partially treated sewage escaping into a street, a basement, or a stream, and the moment it happens your utility is out of compliance with the Clean Water Act. Every operator, starting on day one, needs to know what an SSO is, why it happens, and why fats, oils, and grease (FOG) are the single most common — and most preventable — cause. This guide builds that foundation.
What Is a Sanitary Sewer Overflow?
A sanitary sewer system is designed to carry only wastewater — from toilets, sinks, showers, and industrial/commercial process drains — to a treatment plant. Unlike a combined sewer (which intentionally carries both wastewater and stormwater and may have permitted overflow points), a sanitary sewer is built as a closed system. Nothing is supposed to leave it before it reaches the treatment plant.
A **s