Bending springs are the way to go if you're thinking of making more of these to sell or distribute, they use them for bending PVC conduit. Sand is good but tricky as the volume of the tube increases as you stretch it out. Rock salt I never thought of, good solution if you have problems with the sand getting stuck to the walls of the tube. You could also try to use a smaller hose that fits snugly into the pipe to bend and fill that with sand and seal both ends... Good DIY project.
Giancarlo Podio
Giancarlo Podio
