When designing solids handling facilities, and specifically dewatering systems, often the performance guaranty test for the units is contentious. Variable factors such as: feed solids concentration, volatile solids content, primary-to-secondary ratios, and digester performance can significantly change the dewaterability of the sludge come performance test time. Complicating this is also that performance goals are set during design which is often at least a year prior to actual testing, and, often process changes occur intentionally in the design to meet discharge permits that may have detrimental effects on dewatering performance. This combination of factors reduces the effectiveness of manufacturer sample testing and piloting testing as reliable benchmarks for performance. What can be done? For a site study, for one wastewater plant, large process changes were occurring for the plant to bring it up to meet significantly more stringent nutrient permits and the plant needed the new dewatering facility constructed as a first priority to replace the aging and labor-intensive existing dewatering system. This resulted in two different sludges to be dewatered at different stages of the construction: anaerobically digested sludge and unstabilized waste activated sludge. For this plant, Carollo worked with the screw press manufacturers to benchmark their performance guaranty with Dr. Julia Kopp’s dewaterability test. We will present the results of those early tests, discuss Dr. Kopp’s test results, lessons learned, and compare the results with other facilities that chose more traditional methods to generate their guaranty.