I use MDPE pipe for my hydro, but only at 50psi. We do however use 2" MDPE for water reticulation up to 350psi. At this pressure there were no fittings available and we had to get the joins welded on site. The available fittings went up to 16 bar (~230psi) and are simple enough to use, consisting of a sleeve, O ring and a threaded cap. The fitting goes entirely on the outside of the pipe (no flow restriction).