Sludge (noun):

2: a muddy or slushy mass, deposit, or sediment: such as

A: precipitated solid matter produced by water and sewage treatment processes

We tend to run into sludge situations in the sewer line primarily when there is a “belly” type situation (from what we can tell with our camera due to the liquid build-up). Bellies can be identified by a pipe holding water after the flow has stopped, like a puddle. Bellies are usually caused by geological events such as soil erosion, foundation settlement, earthquakes or by human error such as poor soil compaction or poor installation.

Channeling is another situation that occurs when running water cuts a course in the bottom of a sewer line over time (like the formation of a ravine, canyon, or gully). Sometimes by the time a sewer line channel has become a problem, the bottom of the pipe may be completely gone, opening it up to roots as well as other types of buildup and blockages. This is a common problem in horizontal cast iron pipes. (Source:

Sludge can also simply buildup behind any other type of blockage in an otherwise level line that in many cases hasn’t given the homeowner any problems (like a slow buildup of roots that haven’t been removed—which is another good reason to consider an annual sewer line cable maintenance).

Many times, we can clear these types of lines with cutters and cables, but due to the liquid consistency of sludge, sometimes it requires us to use a hydro-jetter (high pressure water machine) to clear. In most cases, at this point, we will recommend a more permanent solution of line repair or replacement due to the fact that this tends to become a recurring issue.