Having been left with a significant quantity of 16mm underfloor heating pipe I'm toying with the idea of plumbing e house with it too. It has all the necessary approvals and I've sourced adapters to go from it at 16mm to standard fitting sizes but here's my query..

The adapters I find have a brass insert that goes inside the tube. The wall is thick and ultimately this means that at either end of a 16mm outer diameter pipe is a pipe insert that has an internal diameter of circa 6mm

Speedfit pipe has a 15mm outer diameter and also requires inserts in the ends. These inserts are more like 10mm in their inner diameter


What would give a better flow rate over X metres? 16mm o/d pipe plus two inserts at 6mm i/d, or a 15mm pipe with two 10mm I/d inserts


Related is a query over whether a UFH manifold port can supply at the rate of 9litres/minute. I like he idea of just whacking another UFH manifold on the wall and then running a pipe to every point for two reasons.. One that I have all the stuff already and the other each pipe his has just 2 joints so if a leak occurs it's unlikely to be inaccessible

It would be worth looking at the maximum pipes and connection pressures, UFH tends to run at a far lower working
pressure than domestic supply pipe, the last thing you need is a connection blowing off at night when the pressure rises . Its also worth noting potable supply pipe requires to be WRAS approved whereas im not sure the UFH pipe
will be.