I've been told that you can pack the tube with wet sand and you're less likely to crush it at the bend.
But WTF do I know. Never tried it.
A better option is to pack the tubing with salt, not sand. Tape one end closed, fill the tube with salt and tape that end closed.
After bending, take the tape off and knock the salt out. I had to soak mine in water to dissolve the salt packed into bends, then blew the lines out with air. Flushed it with water and blew it out again.
As salt will dissolve in water where sand does not, you have much less risk of introducing sand into whatever system the lines are for.
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