When a Mining Well mines any BC pipe it turns it into a void pipe which would give you a supply of void pipes. (You could convert low value pipes into void pipes (if playing with project e then you could farm emc.))

BuildCraft version: 7.99.17
Forge version: 1.12.2 - 14.23.3.2655
Singleplayer or multiplayer: singleplayer
Steps to reproduce: Place a pipe under a powered mining well