Careful planning, installation and monitoring will reduce the risks of spills and leakages.
Sewer overflows are a daily occurrence in the United States. Clearing, repairing or replacing a pipe usually requires a temporary sewer bypass to divert the discharge from point A to point B and create a work area.
Every sewer bypass project has potential pitfalls. If you’re designing, installing and operating the bypass yourself, follow these tips for a greater chance of success.
Protect people and the environment
Worker safety and environmental safety should remain top of mind with any bypass operation.
- Follow confined space protocols. Anyone working in a confined space such as a sewer should be properly trained, equipped and supervised.
- Encourage hepatitis A and B shots. During sewer bypass setups and teardowns, workers may be exposed to raw influent wastewater that can carry bloodborne pathogens.
- Use a spill containment berm. Placed under equipment, it can capture fuel, oil or wastewater.
Size it right
Determine the maximum anticipated flow and design the bypass system accordingly.
- Create a professional drawing. Visit the jobsite to understand the needs and constraints, then create a professional drawing that shows what the system will look like. Ask your fluid solutions provider for assistance if you need it.
- Check the suction lift. The total dynamic suction lift should be no greater than 28 feet. The recommended minimum suction depth is 6 feet. A suction lift that’s too high or too low can cause performance loss or equipment damage.
- Control velocity. Generally, you don’t want to exceed 12 feet per second.
- Ventilate properly. To avoid rupturing or flattening the discharge pipe, make sure you are introducing and evacuating the right amount of air.
- Select the right pumps and hoses. Diesel-driven centrifugal pumps are the typical choice, but if the suction lift is too great, electrical or hydraulic submersibles may be required.
- Build in redundancy and easy access. Be prepared with backup pumps, and set up your system so it’s easy to swap them in and out. Create good access points for fueling, maintenance and isolation gate valves.
Keep the bypass running smoothly
Take these steps to help ensure your bypass system operates properly.
- Set up monitoring. An experienced, capable worker should be watching the system. Alternatively, save labor costs by using telemetry to monitor pumps. A telemetry system can automatically send alerts for problems involving fuel level, oil pressure, coolant temperature, flow rate, suction and discharge pressure and more.
- Install discharge line gate valves to bring in water for flushing. This can help you contend with blockages and other unforeseen issues. Place the gate valves at the low points where water will collect.
- Keep the pump warm. When temperatures dip below 32 F, freezing water can crack the volute in the pump, disrupting the bypass. Use space heaters, electric blankets or tents as needed to help prevent cracks.
Check and test before startup
Fixing issues becomes much more complex once a system goes live. Reduce the risk of problems with these steps.
- Check all pump lubricant and fuel levels. Don’t let your bypass fail due to a lack of basic pump maintenance.
- Use gauges to check the priming, suction and discharge systems. Outfit the suction system with a vacuum gauge on the priming and suction side and a pressure gauge on the discharge side for continuous monitoring.
- Check the telemetry system if you’re using one. Make sure it’s connected and that all sensors are sending signals.
- Test the bypass system. Fill the bypass with fresh water to test for leaks.
- Attach your emergency response plan/contact list to every pump. Keep it updated.
Follow proper teardown and removal procedures
When the job is finished and it’s time to tear down the temporary bypass, do it right.
- Remove the plug at the lowest flow times. This is generally between 11 p.m. and 4 a.m.
- Keep the equipment in ready position. If the owner’s system isn’t ready to accept the flow, you may need to restart the pumps to avoid serious spills.
- Sanitize and disassemble the system. When the owner’s system is back up, make sure that all equipment is properly sanitized and disinfected with clean water and bleach or sodium hypochlorite. Properly dispose of this cleaning water.