What Does Backwater Level Mean?
Backwater level is the difference between the normal water level and the water surface level resulting from an obstruction to the water' s flow in a gravity flow pipe, such as a sewer.
Such obstructions can result from trenchless installation; for example, failure to fully remove debris from the pipe in a pipe ramming operation or pulling debris into a new pipe as it's pulled through a bore.
Obstructions can also occur as a result of repair materials such as pipe liners, that do not properly adhere to the interior surface of an older, damaged pipe (called a "carrier pipe") undergoing relining or slip lining.