The pump power oscillation caused by slugs in slurry phase polymerization reactors limits production capacity. A bypass line connecting two locations of a loop reactor is suggested in patent literature to dissipate slugs. The optimal design of such bypass lines is studied through a hierarchy of modeling approaches applied to an industrial-scale reactor. In the design process, 1D hydraulic calculations guide the selection of optimal bypass pipe sizes to maximize slurry velocity. 2D CFD simulations provide data on slug dissipation processes. 3D simulations guide selection of optimal installation angle to maximize solid intake into the bypass line. By combining these approaches, a bypass line connecting the second and sixth legs by 6 in. pipes at a 45 degrees angle is found to be optimal for reactor considered here. Such designs achieves high slurry velocity in the bypass line while maximizing slug dissipation, and the approach is applicable for other loop reactor configurations.