Abstract This work presents a workflow applied to 27 wells of the Fortin de Piedra Field in Vaca Muerta that can determine the likelihood of isolation problems during fracture stimulation by analyzing pump-down data and comparing fracturing pressures within the same well, providing a practical method to evaluate zonal isolation without specialized downhole instrumentation. The approach involves a simple workflow that has been applied to analyze 796 plug-and-perf jobs and 11 plugs from different vendors. It starts by categorizing the pressure morphology of pump down diagnostics (water hammer, isolation confirmation, breakdown pressure) to accurately predict if a given job is likely to exhibit lower-than-expected treating pressures and thus, isolation issues. These were tailored with different options based on the available time to have no impact on the efficiency of the operations. Complementary diagnostics such as step-down rate tests and pre/post frac water hammer analysis was also conducted to corroborate the findings. By applying this consistent workflow, the authors were able to determine with 81% accuracy whether a given job was likely to exhibit isolation issues. This assessment was made solely based on diagnostic data collected during pump-down operations, without the need for specialized downhole monitoring equipment. A simple calculation for the limited entry designs employed suggests that the most likely source of the difference between expected and real treating pressure during the job must be an increased flow area inside the casing, indicating potential plug failure. With this method, the authors were able to get an early warning when the proportion of stages with isolation problems became higher than usual. Surface tests carried out on those plugs confirmed these findings. Additionally, parent wells showed higher intensity Fracture Driven Interactions from stages where isolation issues were identified. This paper presents a cost-effective workflow to evaluate zonal isolation in unconventional wells without the need for advanced downhole diagnostics. By applying this workflow, operators can better select and identify the most suitable plug for their operations, improving effectiveness of fracture stimulation treatments.