For example, you can use an empty barrel to pick up lava source blocks. This does not actually fill the barrel, but does destroy the fluid block, allowing you to clear an area of non-whitelisted fluids very quickly. Barrels probably shouldn't be able to pick up non-whitelisted fluids.

Note: if the raycast hits a block it will just place the barrel instead of picking up the fluid

Meta Info

• TFC Version: 1.7.17.175
• No other mods required

This issue has been fixed in the current MC 1.18 versions of TFC - understanding that the tag is a replacement for the whitelist.