In this investigation, a self-made low pressure device (up to 100 psi) for creating hydrodynamic cavitation was optimized by using the Weissler reaction. Optimal upstream pressure for the reaction was obtained for a single line system (without bypass) as 29 psi. The effects of the centrifugal pump and the bypass were significant as compared with the effect of the restrictions investigated. Therefore, the use of more lines is proposed. The effects of different restrictions (valve, one-hole plate, and multi-hole plate) were investigated and multi-hole plates show better efficiency.