Local ACE Hardware actually had all the goodies, including plugs & schraeder valve fittings for pressure testing.  Even lent me the crimping pliers gratis.

The reason I ran short is cuz I changed the system design a bit on the fly, which is quite typical of me.  The entire slab sits on 2" of styrofoam, called Insulworks: these are 4'x4' pieces w/ grooves milled so the PEX just snaps in & is secured by plastic staples.  Two zones of the hydronic system are purely distribution: (1) back bedroom, office, and part of living room; (2) bathroom, mudroom hall, and master bedroom.  Third zone is the troublemaker.  It leaves the manifold, warms the bulk of the living room, then does many tight turns in the solarium, where dark concrete and sloped glazing should mean a net temp gain on cold sunny days.  So it's a mix of distribution and collection.  Then I was going to return to the storage tank, but figured heck, may as well use this reheated glycol to warm the kitchen.  That's when I ran short.  Choices became: overextending loop (2) to carry the kitchen; adding a fourth zone; or splicing more PEX to loop (3) and putting that reheated fluid to good use.

The bathroom floor, BTW, is a product called Warmboard: basically 1-3/8" thick OSB with an aluminum sheet surface and tracks for the PEX.  Haven't quite sorted out the controls yet: it's going to be pretty basic, with maybe one floor temp sensor in the LR and I'll balance the other zones by tweaking manifold valves manually.  Not putting thermostats or electronic valves on each loop.  That's an expensive pain, and uses parasitic power.  The solar HW collector will have its own pump and differential thermostat.  Or I might just slap a 12VDC slow pump and 50 watt solar panel right on the collector and call it good.  Glycol in both the collector and hydronic systems; domestic hot water is in a 60 gal tank with dual stainless heat-exchanger coils inside.  After six months of futile searching, I finally found a reliable supplier of solar tanks at a decent price: Tam Jass tanks from SPNW in Oregon.  Thermomax wanted about 2.5 times as much for a lesser tank.  And SPNW will cut in bulkheads for water heater elements for only $60 per, so my wind turbine dump loads are taken care of.  The the DHW leaves the tank and goes to a demand LP gas water heater which modulates to zero BTUs if the water is hot enuf.