What Does Drop Connection Manhole Mean?
A drop connection manhole is one that is positioned where a sudden drop in the elevation of pipelines occurs. The incoming pipe – the influent line – is higher than the outgoing pipe – the effluent pipe. The change in elevation of the pipelines may occur before the manhole (which is then known as an external drop connection manhole) or inside the manhole (which is then known as an internal drop connection manhole).
Trenchlesspedia Explains Drop Connection Manhole
While the EPA's generic code for manholes and sewer systems specifies that internal drop connection manholes are not the optimum choice, many cities still have what are known as "beaver slide" connections within their manholes. "Beaver slide" refers to low-angled riverbanks down which beavers can slide to enter the adjacent river. This type of connection resembles the beaver slide in that it is a low-angle connection between the influent pipe and the effluent pipe that occurs within the mantle. This makes these manholes internal drop connection manholes by default.