What is a Sewer Bypass?
When sewers collapse or need repairs, the flows must be bypassed, leaving the damaged pipe clear to be replaced or relined. Pumps reroute wastewater while the rehabilitation proceeds.
Bypass pumping is a system of pumps, hoses and pipes that are used to divert the flow from a section of pipe being repaired, replaced or rehabilitated. Pumps are needed to temporarily divert fluids from one source to another.
Temporary bypass systems include open systems, involving suction from sources open to the atmosphere pumping to other open sources; closed systems, taking suction from a closed source with pressure to another closed source; or a combination system, taking suction from an open system such as a manhole and pumping into a closed system such as a force main.
Possible Causes
Municipal and private sanitary sewer collection systems are in a constant state of repair and maintenance.
Bypasses can be caused by accidents, such as pumps failing or pipes bursting. Sometimes wastewater operators may be forced to bypass if they have to shut down equipment for emergency repairs and there exists no feasible way to reroute or contain the wastewater.
Heavy rains, rapid snow melt or flooding also can cause bypassing, when more water gets into the sewer system than it has the capacity to move (system overload). Bypassing in this case sometimes is used as a “safety valve” to keep sewage from backing up into homes.
Wastewater collection systems require periodic maintenance and repair, and occasional replacement. Sewers deteriorate from internal and external forces. Internal forces include crown corrosion and attack by corrosive or abrasive materials contained in the wastewater (e.g., industrial wastes). External forces include overburden (e.g., soil and traffic), groundwater buoyancy, frost heave, penetration by surrounding tree roots and differential soil settlement.
Performing Bypasses
A pump company can act as a subcontractor not only to provide pumping equipment; it can handle design, setup, monitoring and installation, providing specific application engineering expertise to each project and thus a complete bypass pumping system. More municipalities and customers are lacking laborers to do these projects and looking to pump companies to provide more than just equipment rental and sale.
The following are some sewage bypass fundamentals that should be considered in evaluating all bypass projects. Several necessary steps must occur to complete a successful bypass.
- Design.
- Calculations of static lift, friction losses and flow velocity
- Bypass pump sizes, capacity, number of each size to be on site and a good vendor
- Size, length, material, location and method of installation for suction and discharge piping
- Downstream discharging plan
- Equipment requirements and customizations—consider phone dialers/monitoring systems; automatic start/stop systems designed to monitor influent fluid levels and initiate the startup/shutdown of pumps when needed; temperature requirements; manifolds; sewer plugging methods; and special requests.
- Estimate and determine job scope, including the number of people needed for setup.
- Provide appropriate submittals and detailed plans.
- Conduct job walk with the superintendent or person in charge.
- Review logistics/staging; method of noise control for each pump; landscape barriers; safety regulations; permitting and code requirements; road crossings; power sources, diesel or electric-driven equipment.
- Job setup.
- Set up pumps, pipe fusion, discharge and suction hose
- Administer system testing
- Job site monitoring.
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- Sewage spill violations are a serious matter that the sewer bypass provider must take all precautions to avoid.
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- Completion/teardown.
Success Support With a myriad of tasks and technical executions, it is recommended that a bypass representative specializing in design, estimation and setup be involved from the onset of a sewer bypass project.
Listed above are the basic necessities to complete a sewer bypass. The basics are numerous, and this does not take into account the numerous other variables that often will be encountered.
A truly successful sewer bypass requires a professional with experience and expertise who knows the tips and tricks to be aware of when conquering an engineered undertaking such as a sewage bypass.
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