Bypass Pumping Details Often Taken For Granted

By Jeff Griffin, Senior Editor | January 2011 Vol. 66 No. 1

Stroud said general contractors that specifically focus on water and wastewater often are more successful with bypasses than basic general contractors.

“Understandably,” Stroud said, “when the economy started declining, we noticed a trend for general contractors without extensive bypass experience bidding on this specialized work in order to augment their income. Many contractors without fundamental bypass experience have required more guidance and product training or have subcontracted the job to get it performed properly.

Stroud said there are several essential steps necessary to complete a successful bypass, and a specialist in design, estimation and set up always should be involved. Factors to consider in planning include, but are not limited to, source of flow, average flow and peak flow potential, properties of the influent and the discharge point.

Essential elements of a bypass system include pumps, sizes and types of piping and fittings, check and gate valves and controls.

“Some pump users do not thoroughly understand the efficiency portions of a standard pump curve and the importance of sizing a pump for maximum efficiency,” said Stroud. “Having a pump that does not exactly meet job requirements may work for some applications, but this is not the case for sewage bypass systems. The appropriate pump must be precisely defined, and this is accomplished by examining the pump’s curve -- the total head developed by the pump at various flows.”

Bypass contractors
BakerCorp, with worldwide operations that include bypass pumping and excavation shoring, provides turnkey bypass system services.

“Generally, bypass requirements are specified by the owner, usually a municipality,” said Chuck Rickman, vice president of product development. “The details of how that is accomplished are usually left up to the bypass subcontractor such as BakerCorp. We provide pumps (including sound attenuated models), hose, fittings, setup, pump watches when required, berms, generators for electric driven pumps, day tanks, remote monitoring capabilities, TDH calculations and process flow diagrams.”

Rickman said to plan and design a bypass system it is essential to know normal and peak flow rates, amount of suction lift, distances the sewage must be pumped, and elevation changes. Are there noise restrictions that dictate the use of sound attenuated diesel driven pumps, or are electric driven pumps required? Are there space limitations that would restrict the size of pumps or how piping is run from manhole to manhole?