I drew a micro overflow so I can use it on my aquarium but I’m having a hard time using support because there is a tube that has to be hollow. This is how it looks like:
100% infil will help eliminate (or reduce) leaks, for sure, but no garauntees with FDM printing. As for printing without filling the tube with support, I would consider cutting the whole thing in half and gluing it together after it is printed (granted, then you have a new poetntial leak to elimiante, but it will be easier to get that seam filled than it will be to clean suport matieral out of an enclosed tube).