sfboarders is right. it has nothing to do with the material they are made from. it is metric plumbing. even here in Australia we use standard plumbing and require the use of metric to standard conversion fittings. Luckily alot of the LFS are now stocking the metric fittings required to modify the plumbing on alot of these all-in-one tanks that are made in China.Question, where did you get all the tubing and fittings for the union ball valves? Mine are uPVC 1/2” true union ball valves and because of the uPVC, they won’t fit any of the PVC we have here in the states.
I’m finding it extremely frustrating they used this uPVC material because none of it fits the normal PVC fittings.