Up to 9 different items can be selected per output, with 5 outputs available (one color is reserved for input). If an item has no match, it will be routed out of a color that has no filter, or if all colors are used the item will be rejected and dropped on the ground.
The Diamond Pipe cannot be Waterproofed.
Rarely, Diamond Pipes experience a client side glitch, causing items to appear leaving the Diamond Pipe in random directions without being sorted, like a normal Stone Pipe would act. The items continue on the Client side until they reach a Chest or similar container. However, opening the chest reveals that all items are sorted correctly after all. The glitch appears on all clients until the server is restarted and does no harm at all.
In the GUI, multiples of the same item can be placed in a single row to affect relative probabilities. For example, if 2 Cobblestone is placed in yellow, and 1 Cobblestone is placed in green, 2/3 of the Cobblestone will go to the yellow output, and 1/3 will go to the green output. This can be used for gambling machines.