Diameter Loss

Diameter loss is the defect most operators never see coming, because the pipe itself isn't damaged. The walls are intact. There's no crack, no collapse, no root intrusion. But the inside of the pipe is no longer the size it's supposed to be — and that's a problem your building feels long before anyone identifies the cause.

What causes it:

Grease, scale, sediment, mineral encrustation, and protruding tap connections all reduce the usable diameter of a line. In commercial properties with food service, grease is the dominant cause. In older buildings, mineral scale and corrosion-driven encrustation take over. In clay and early PVC mainlines, the pipe itself can deform under soil load, going from round to oval and losing capacity that way.

Whatever the cause, the result is the same: the pipe can't move what it used to move.

What grading tells you:

Diameter loss isn't visible from a manhole or a cleanout. You can't tell from the surface whether your line is at 95% capacity or 50%. A CCTV inspection with measurement capability tells you exactly how much usable diameter you've lost, where the buildup is concentrated, and whether the cause is something cleaning can fix or something that requires repair.