Definition - What does Bypass mean?
A bypass is a system of pipes and valves - a manifold - to divert the flow around a specific piping or valve structure. It's also a temporary diversion of flow around a part of a water or sewer system that allows flow to continue when the primary line is blocked or undergoing repair or rehabilitation.
Using a bypass to direct flow around a problem area ensures continued water or sewer flow when lines flow can't be diverted from its destination.
Trenchlesspedia explains Bypass
For example, if the a break, blockage or repair project impacts the flow of municipal water to homes in a specific area, a bypass can divert the flow to temporary lines that guide the flow around the problem area. The bypass consists of a bypass valve that shunts the flow into a temporary pipe. The temporary piping carries the flow around the affected line and reconnects to the primary line at a second valve. Opening the bypass valve allows the flow to enter the temporary pipe and opening the second valve allows flow to re-enter the primary pipe at a point beyond the problem area. When repairs are completed, both valves are closed to prevent backflow into the temporary line. Flow will be interrupted only long enough to install the bypass, rather than for the whole time required to complete a repair or rehabilitation project. A sewer line bypass generally requires a pump to move sludge into and through the bypass. In this case, the pump acts as the valve at the beginning of the bypass.