Tutorial: How to Model Flexible Water Cooling Tubing.
How to model PVC tubing for the purposes of PC water cooling models in SolidWorks:
Assemble hardware and fittings as required.
Create the tubing part and open a sketch on any plane perpendicular to the fittings (i.e., looking at the side of the fittings, not the top or bottom).
Use "Convert Entities" to convert the edges on the base of the fittings, then make these construction lines.
For a fitting which is perpendicular to the skecth plane, create a centreline going down from the midpoint of the converted entity. The length of this line does not matter.
For a non-perpendicular fitting, first draw a centreline between opposite points on the ellipse.
Then draw another centreline which is perpendicular to this. The length of this line does not matter.
Draw a spline which connects the midpoints of the two centrelines. Don't be tempted to add spline points - this will result in an unnatural curve.
Select the spline and the perpendicular centreline, and add a "tangent" relationship.
Then repeat with the other centreline.
Adjust the spline handles to create a natural curve.
Exit this skecth, then repeat the entire process on a different plane.
Use the "Projected Curve" tool to create a curve using the two skecthes. Check the preview to make sure it looks correct.
If the curve disappears after you press the tick, you may have "view curves" disabled.
Open a skecth on the face which the curve begins, and draw two circles which represent the inner and outer dimensions of your tubing.
Exit this skecth and click the "Swept Boss/Base" tool. Select the circles skecth for "profile" and the curve for "path". Select "minimum twist" for the "path alignment type".
Final model rendered in KeyShot: