Date: [Insert Date] Subject Property: [Insert Address] Prepared by: [Your Name / Plumbing Professional] Issue Type: Sanitary Drainage System – Main Building Drain / Building Sewer Blockage 1. Executive Summary A main drain clog refers to a partial or complete obstruction in the primary 3–6 inch diameter pipe that carries all wastewater from a building’s internal plumbing (sinks, toilets, showers, laundry) to the municipal sewer line or septic tank. This condition is critical, as it affects all fixtures on the same branch and can lead to sewage backup, structural damage, and health hazards.