Despite their name, pipe bending springs do not actually bend pipes. In fact, what they actually do is help you to not distort or crease your pipes during manual bending by providing a stable internal or external structure.
This is what a creased pipe looks like. Inserting a bending spring into your pipe prior to bending will reduce the likelyhood of this from happening.
This is what a correctly bent copper pipe looks like. The pipe bending spring has kept the pipe walls from creasing and distorting under strain.
It is very useful to be able to bend copper piping as you will not always want to use a pipe joint, especially if the pipework will be inaccessible at a later date.
Being able to bend copper pipes manually will also forgo the need for welding or soldering.
What types of pipe can I bend?
Internal pipe bending springs should only be used on annealed (soft) copper piping of 15mm – 22mm diameter. For pipes with a smaller diameter, it is advised that you use an external pipe bending spring.
You can also use pipe bending springs to bend plastic (PVC) piping and electrical conduit.