This is probably already fixed, but please take a look and close it if it is..

http://pastebin.com/06vQQP3j

Not too sure I understand what's causing an AbstractMethodError in this case..

Weird! And good find. Are we running against an out of date forge maybe? Or is CB in the wrong?

Aha!
java.lang.AbstractMethodError: TileMultipart_cmp$$7.drain(Lnet/minecraftforge/common/ForgeDirection;Lnet/minecraftforge/fluids/FluidStack;Z)Lnet/minecraftforge/fluids/FluidStack
EDIT: yup, that was it. https://github.com/Chicken-Bones/ForgeMultipart/blob/master/codechicken/multipart/scalatraits/TFluidHandlerTile.scala does not provide FluidStack drain(ForgeDirection from, FluidStack resource, boolean doDrain)

I was testing it with 1.0.0.219 (it probably autodownloads most recent version). Looks like it's missing from implementation. I guess will create issue on multipart.

Closing here, since we are using interface correctly.

I talked with KingLemming about this days ago, it was because fluiducts shouldn't be drained from, but he would be making them undrainable in the future.