[bombela]

pexuniverse and supplyhouse are the two places I have used for the material.

Open loop is easy to deal with. I can use the same water heater. It's the bay area in California, so the system works for 1/3 or the year. Rest of the time it's simply buffering the cold water supply to the water heater. So no water stagnating, not air vent needed, and it's always filled up by definition. Further more because it's at the street water pressure, the pump cannot cavitate, so it last longer and is quieter.

I only used manual tools to crimp the rings. Sure you need some force but your body will build muscles. And since PEX is flexible you don't use that many fittings anyways. It's really childs play.