I have never seen flexible PVC. However It does not seem like a good idea to use flexible piping for the suction side of the system especial y with the weight of fill on top of it. even on the pressure side there could be problems with the possibility that the weight of the fill on top of the tubing would eventualy flatten it.
It is safer living by buried power lines because they won't fall on your house or car in heavy winds or ice storms.
a return address should have 2 lines
NONE!!!! Zinc flakes are not good for a hydraulic system. Black pipe may be used for non-pressurized return and suction lines only.
It will be on the suction line (larger of the lines) between the compressor and the evaporator.
spline
Some products made of nylon is flexible. This includes leotards, fishing lines and guitar strings.
suction line liquid line
Nasca Lines The Buried Secrets - 2010 TV was released on: USA: 1 March 2010 (TV premiere)
What may be done for gage lines if the flexible ones cannot be made leak free
What does your local code say
Many people who do drafting ( by hand, not CAD) use what is called a flexible curve. This is often a lead core rubber or plastic coated flexible device that helps draw curved lines. They come in different sizes.
Supply is above and return is under.