BuildCraft version: 7.99.15
Forge version: 14.23.2.2611
Link to crash report or log: N/A
Singleplayer or multiplayer: N/A
Additional information:

When placing a non-connecting tank (using canConnectTo() public method) on top of any other tank; if there is any fluid in the upper tank, the lower tank does not render the top face of the fluid.