Cut the desired curve out of a piece of 1-inch plywood using a jigsaw. If the diameter of your pipe is more than 1 inch, cut additional pieces of plywood and glue them into a single piece with wood glue. Clamp them together tightly until the glue dries.
Screw the plywood to the edge of a work table with wood screws. The curved end should face the center of the table.
Place the pipe against the plywood, with one end positioned even with the end of the curve.
Screw a scrap of two-by-four to the table on the other side of the pipe, preventing it from moving side to side.
Grip the other end of the pipe and apply steady pressure, bending it into the shape of the curve. Work slowly so you don't create kinks in the pipe.