Robert Kolnes, TBE, CxA, TABITT Jonathan Stranierois, CxA, BCC Management All to often within the construction phase of a project, the flushing of hydronic systems is scheduled to be performed, albeit without sufficient detail being provided within its project manual. Specifications generally leave interpretation to the contract professional and who’s to know better than the mechanical contractor’s chemical treatment company? A Commissioning Provider firm, with ability to serve as a design team member, can become a contributing member to the contractor’s team by working with the mechanical contractor in developing and initiating a thorough flushing plan. Our case study highlights extreme elements in the remediation of chilled and heating hot water piping systems, providing for efficient operation of a newly constructed central plant cooling and heating delivery systems through to renovated air handling systems. Here are some common pitfalls: The flush pump, usually house pump, is not sized adequately for the volumetric flow necessary to achieve >5fps throughout mains and branch piping The flush pump is not operating at sufficient speed during the flushing procedure, a process of monitoring to ensure variable speed drives are not adjusted Various valves within the system were never opened Strainers became clogged in the middle of the process and the contractor is not inspecting the system to identify which strainers require spot-cleaning during the process Too many uncontrolled coil bypass pipes resulting in short circuit of flow, specifically where bypass pipe is equivalent to coil size piping Air entrapment within piping systems leading to potential air lock across sections of the hydronic flush loop