Anywhere. It can only matter when using RP2 fluid pipes and only if block has more than one tank. For example in the fermenter you put water in the side that have blue liquid as seen from solid sides and you get biomass from the side that have green liquid (doesn't matter with liquiducts, tank (un)loaders and waterproof pipes).Pumping water into a Carpenter, does it have to go into the top, or can it go in elsewhere?