Drain & Sewer
Pipe Belly (Sag)
A pipe belly (also called a pipe sag) is a low spot or downward depression in an underground sewer or drain line caused by soil settlement, inadequate support during installation, frost heave, or soil erosion beneath the pipe. A sagging section of pipe collects water, solids, and debris that cannot drain forward by gravity — the pipe's natural slope is interrupted at the belly. Solids accumulate in the low spot and form recurring blockages that keep coming back even after clearing.
Pipe bellies are identified by camera inspection. Mild bellies (less than half the pipe diameter) may function adequately with regular cleaning but will always be a recurring maintenance point. Severe bellies hold standing water permanently, allow sewer gas to accumulate, and cause chronic blockages. The only permanent solution is excavating and relaying the pipe with proper slope and bedding — a more significant repair than jetting or lining.
What This Means for You
If your sewer line is clogged repeatedly in the same location and jetting only provides temporary relief, a pipe belly is a likely cause. Camera inspection will confirm it. Before any sewer repair or replacement work, ask whether a belly is present — it affects the repair strategy significantly.
Related Terms
Sewer Line · Lateral Line · Camera Inspection · Hydro Jetting