The Vis Pump sets up a constant flow of vis or taint in a series of conduits.
Suction is only applied from the front of the device (the end with the pumping animation). It has a small internal store for any vis or taint it has pumped. To extract vis from this store you need to connect conduits to its back which in turn needs to connected to some suction causing device. You can use a series of pumps to move vis over large distances.
Vis Pumps apply a suction of 20 TCB from their front, though this can be increased by connecting bellows next to them. The pumps orientation can be changed with Tinkering Tools.