Bypass

Published: | Updated: August 12, 2020;

Definition - What does Bypass mean?

A bypass is a system of pipes, pumps, hoses, and valves that help divert the flow from a pipe section that is under repair or rehabilitation. This temporary diversion allows the flow to continue when the primary line is blocked for rehabilitation.

Bypass pumping is often used in sewer repairs to prevent sewerage from backing up into homes while work is being executed on existing infrastructure. The advantage of bypass pumping is that the water or sewer flow to homes and offices remains uninterrupted during repairs allowing contractors sufficient time to complete the job.

Sewer pipes and water mains require regular repair and maintenance work, and sometimes replacement, in order to keep the system in working condition. Trenchless rehabilitation methods are excellent ways to do so in lesser time and cost and minimal disturbance to the ground surface.

A bypass is also known as a manifold.

Trenchlesspedia explains Bypass

While rehabilitating sewers, the flow cannot be simply diverted, it has to be bypassed around the defective pipe. For this purpose, the pumps are deployed upstream from the defective pipe and a temporary pipe is installed from the pump upstream to a section of the pipe downstream.

For proper pump and equipment selection, the contractor needs to know the peak flow, pipe depth, pipe size, work duration, and problems with access. Other issues that a bypass project can face are friction losses in the temporary pipeline, sewage spills and excess line-pressure, among other problems.

Bypass equipment

The bypass consists of a bypass pump, pipes, and valves that shunt the flow into a temporary pipe. The temporary piping can be of high-density polyethylene (HDPE), polyvinyl chloride (PVC) or steel, and valves are such that they do not let trash in the sewage entangle.

In deeper settings where the lift is greater than 25 feet, submersible pumps may have to be used as they are not limited by suction lift but push the water up. Where the suction lift is less than 25 feet, the bypass can be carried out with an above ground self-priming or prime-assisted pump.

How Bypass Works

The bypass valve 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 the 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. The 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.

Bypass Plan

A good bypass plan should include the following:

•Startup and operation procedures.

•Monitoring program.

•Contingency plan for sewage spills.

•Monitoring log.

•Qualified contractors and operators.

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