Last year I installed my EKO 60 with 500 gal of storage by myself, using rigid copper, except for one underground PEX line running to a second house. This year, I finally hope to find the time to improve the heat delivery part of the system, planning to plumb in radiators and finned tube baseboard to gradually replace the plenum HX's, so I can get more flexible zone control and better heat delivery with lower water temps. Anyway, I am planning on using as much PEX tubing as I can for the various plumbing jobs ahead. I have become totally confused at times with the myriad of different PEX manufacturers and fitting types. I bought the Wirsbo expander tool last year (used, cheap on EBay) and was planning on using the Wirsbo PEX tubing again. However, I am finding so many other choices for tubing and fittings out there - crimp systems, shark-bite style, etc. all of which seem to be limited to working only with certain brands of tubing. I also have to do some regular household plumbing for the hot water tanks, etc. and for these I will use non O2 barrier tubing. I saw some nice Vanguard press-type fittings at Lowes that were expensive, but easy to use. This is a tall order, but can anyone give me a big-picture overview of the main families of PEX fitting types available, and whose PEX tubing they are inter-compatible with? Before I start on this next major phase of the heating project, I want to make sure I understand the various options open to me in selecting the best PEX system to use.