Polyethylene tube is manufactured from F.D.A. approved resins. It has very low moisture absorption. It is fungus resistant, non-corrosive, and highly resistant to stress cracking. It is available in two types, low and high density. Low density provides flexibility and high density, while not as flexible, has a higher temperature and pressure rating.
Check all tube prior to installation for defects, kinking and discoloration which could be an indication of old age. The few moments it takes is well worth it. Make nice clean 90 degree cuts for ease of installation and to improve seal. Use brass inserts in tube when using compression style fittings to stop tube collapse. Always check for leaks on completion.