If you need to bend a pipe fill it with dry sand and seal up the edges carefully to prevent sand from spilling. Then begin to bend the pipe.
The steps above help to get any pipe bends and not to flatten the pipe in the place of bending.
Thick-walled pipes are more difficult to be bent. To make the process easier you should heat the place of bending. Put on protective gloves, otherwise you can burn your hands.
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