The Spout can be filled with up to 1 bucket of any one liquid via Fluid Pipes. It will then spout the fluid at appropriate items that pass under it via a Conveyor Belt or Depot. The spout takes 1 second to process an item regardless of the amount of fluid used, though delay between fills may be cause by the time it takes the spout to fill back up.
The Spout can fill Casting Tables and Casting Basins from Tinkers' Construct. It will not partially fill a table (will only fill if the amount of fluid is greater than 1000mb)[1].