Just bigger in this case isn't enough. You need to also consider the radius of the bend especially on the inside or the corner.
FM1.png
SO this is after running Follow Me on your profile using the path. Notice in the elbow there are some little edges. If you run this and then orbit inside the wall of the pipe you'll see that there are some faces in there. There are edges that only bound one face, not the required two, so the extrusion would fail the requirements for being considered solid. Below the pipe I put an offset edge aligned with the side of the elbow at the inside of the bend. You can see it is very sharp. I expect if this was a piece of PVC pipe that you heated and bent, you would fine that radius too tight.
In any case you can select all of the geometry of the tube, right click and choose Intersect Faces>With Selection to create the required intersection where those tiny faces are and then delete them making sure you don't leave any holes or hidden orphan lines and when you make it a component, it should be solid.
I've attached the elbow. I made the outside diameter of the pipe 1-1/2 in. Is that correct? At least it is a solid.
elbow_is_a_solid_1.skp