There seems to be a problem with buckets interacting with BuildCraft machines, see http://mod-buildcraft.com/forums/index.php?topic=2.0. Seems due to a Forge problem already reported under MinecraftForge/MinecraftForge#965.

Presumably fixed by MinecraftForge/MinecraftForge#967, integrated in build 1034. Closing.

I just built against forge 1034, it didn't solve the issue, unfortunately.

Damn. Could you see why?

I didn't have a lot of time to play with it last night, but it looks like only part of the pull request made it into that commit. TinkersConstruct is also impacted by this bug, and this build didn't fix the issue for them either.

There's this from the guy who made one of the PRs:

tested, getFluidForFilledContainer still outputs null, the "data" var got from the HashMap always is null

Looking at forge, there's still work in this area. One pull request on the forge has been sent for this purpose: MinecraftForge/MinecraftForge#985

This seems to have been fixed in Forge 10.12.0.1045, according to the changelog.

And yeah, I can confirm that it has been fixed in that version of Forge. I have tested it, and this bug has been fixed.

Can someone close this now?

Closing :-)