I just made some brackets for water tubes I used at home. The brackets fit tight on 16 and 26 mm OD water pipes, while not pressing them to the wall.
Please consider which material you use. PLA starts getting soft at around 60°C. So for tubes which get warm better use ABS. For getting stronger parts I put wall line count in Cura to 5 -> then it only prints walls resulting in flexibel and strong parts.
Edit: In the picture the 26 mm OD version was wrong, as I did not consider the new wall distance. I just uploaded the redesigned version.
Plus I added a version with tighter fit and less used material.