As I understand it - building regs mean that any plastic pipe to be buried in screed needs to be in conduit so it can be replaced. Therefore I have bought - 15mm PEX barrier coil pipe. - 15mm conduit and - I've also bought this conduit elbow. https://www.screwfix.com/p/jg-speed...W0V4c2UX669nCB9-CNAaAnlmEALw_wcB&gclsrc=aw.ds As I understand it, I should be able to thread the 15mm PEX pipe in the conduit and then both through the elbow. However it doesn't. You can get the pipe through the elbow on its own, or the conduit on its own but not both. If this isn't right, how do you connect the conduit to the conduit elbow? thanks to any responders!