We investigate the bending loss and propagation characterization of hollow pipe polymer terahertz waveguides, based on 3D electromagnetic simulation and systematic experiments. Bending loss and propagation attenuation of pipe waveguides are investigated for various core diameters and radius of curvature over a wide frequency range (100-500 GHz). Our results indicate that waveguides with larger core diameters or larger radii of curvature suffer lower loss, with the lowest loss at or near anti-resonant frequencies, with typical values such as attenuation constant of a straight Teflon waveguide as low as 0.29 m(-1) with inner diameter 14 mm, outer diameter 16 mm; and minimal bending loss of 0.45 m(-1) with a radius of curvature 50 cm and inner diameter 14 mm, outer diameter 16 mm. Based on the systematic experimental and simulation results, we propose and test a simple relationship that the propagation constant of curved waveguides may follow, which could serve as a design guide for fabrication of hollow pipe polymer waveguides for efficient and long-distance transmission of terahertz electromagnetic radiation.