To cut 3 joined pipes in different planes in Grasshopper, you can follow these steps:
1. Start by defining the 3D model of the joined pipes in Grasshopper using pipe components.
2. Create three different planes using the "Plane" component in Grasshopper.
3. Use the "Split Brep" component in Grasshopper to cut the pipes using the planes created in step 2.
4. Connect the output of the "Split Brep" component to the preview component to visualize the cut pipes.
This process will allow you to cut the 3 joined pipes in different planes in Grasshopper.
\textbf{Answer:} The joined pipes can be cut in different planes by using the "Split Brep" component in Grasshopper.