Ins and Outs of Sewer Bypass
Sanitary or Sewer Bypass
NCS Fluid Handling Systems provides a wide variety of essential services to both industrial and municipal applications.
When municipalities plan on upgrading existing sanitary system lines, one thing to remember is that the flow can't simply be turned off to facilitate the work needed to rehabilitate an existing sewer; instead, flow should be diverted. Over the years, this situation has create a huge challenge for these projects. How does the municipality continue to deliver services or prevent closing roads and disrupting nearby communities and businesses while the contractor is performing rehab or replacement work?
Sanitary systems still need to be used
When the decision is made to perform sewer rehabilitation, it is typically to replace aging or insufficient pipelines. The solutions require that the waste products be diverted and a temporary system is put in place. NCS Fluid Systems designers accomplish this by deploying pumps to temporarily bypass piping and valves upstream from the sewer pipes that will be replaced and then to re-enter the sanitation system downstream of where the work is being performed. The size of the system is calculated based on peak flow which varies depending on the number of homes and businesses along the section of a line. The amount of waste material moved can exceed thousands of liters per minute!
NCS Fluid Systems designers have years of systems design and experience, which is useful as sizing the line is a critical step. Since the amount of waste material required to be bypassed varies from time to time throughout the day, the temporary system must accommodate this changing flow. Typically, the peak is calculated using flow meters, and peak flow is usually early in the morning and again in the evening when residents return home. This design calculation of peaks is crucial to the project success. If the flow is not calculated correctly and the system is undersized, the pumps or piping may not be able to keep up and sewage spill may be the result, which leads to many problems for everyone.
Pump selection may also vary
NCS Fluid System designer and installation crews consider project specific situations such as the depth of the sewer system or distance of bypass, as this quite often determines the size and type of pump(s) and ancillary valves, pipe, and other equipment needed. For instance, when a sewer line is buried deeper than 7.5 metres or approximately 25 feet, the designers may select a submersible pump to handle the added head pressure. In contrast, for systems not as deep, an above-ground centrifugal pump with a suction hose lowered into the manhole may be selected.
Flow calculations are only a part of the overall operational considerations that NCS Fluid Systems designers review. Other considerations include:
- Are there municipal noise ordinances?
- Road access - NCS offers engineered road crossing to accommodate traffic flow
- 24-hour system monitoring by skilled technicians
- Equipment placement - is signage and traffic control required?
- Environmentally sensitive areas may require seamless piping systems such as HDPE piping to be assembled, reducing possibility of leaks
In today's market, a sewer system upgrade project may be an open cut replacement or a trenchless lining technology rehabilitation, but the one thing that won’t change with any rehabilitation is the need for a properly designed bypass system that incorporates the proper pumps, piping, and additional equipment.