Multi Fluid Identifier
The 
Multi Fluid Identifier is one of the most useful tools in the entire mod, used to change the type of fluid in pipes or machines.
Craft
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Operation
To select a fluid type, hold SHIFT and press RBMK, then enter the name of the desired liquid. After that, select the liquid by clicking on it, and a blue frame will appear around it. You can also save two liquid types in the Multi Fluid Identifier and switch between them by pressing RMB while holding the Multi Fluid Identifier.