Flow characteristics with gel reaction of 10 mass% PVA and 3 mass% borax solutions in a Non-element mixer were experimentally investigated. The mixer consisted of a transparent main flow pipe and transparent branch flow pipes that were connected vertically to the main flow pipe. The PVA solution was supplied to the main flow pipe at a constant inlet pressure 20 kPa. The Reynolds number of the main flow (Re) was varied from 0.5 to 10.0. The borax solution was dyed blue to visualize the flow patterns and was injected periodically from one of the branch flow pipes at a mean speed of 40 mm/s. A pressure sensor was used to measure the pressure variation at 100 mm upstream from the first branch flow pipe. When Re was low, the borax periodically formed a capsule-like slug similar to those that occur in multiphase flows. As Re was increased, the borax capsule was stretched by the shear stress of the main flow and adhered to the upside wall of the mixer. At Re = 10.0, the pipe was prone to becoming blocked by excess gel product, which resulted in the pressure increasing to the inlet pressure of the system.