Plumbing - PEX Pipe
For potable (ie drinking) water you need PEX tubing that DOES NOT have an oxygen barrier. The type with an oxygen barrier is just for use in radiant heating systems where the heating system uses cast iron parts and you want to avoid rust. If you are certain you will never have cast iron components in your heating system then you can use NON-oxygen-barrier for the radiant heating system too. My advice is to just avoid using cast iron, ie use NON-OB PEX everywhere.
Typically use 3/4" to go to the manifold and hot water heater, and then 1/2" to the various fixtures via a manifold.
The best brand is AquaPEX. The best type is PEX-a. AquaPEX is the only PEX-a material available for drinking water.
There are various connector types that can be used with PEX tubing, but here is my recommendation. Use the crimp connectors/fittings, but use them with stainless steel clamp rings (rather than copper crimp rings). Crimp style fittings are the most common and affordable type of PEX fittings and can be found in most home centers and online stores. It will cost you about $70 for a clamp tool (but this is less than a crimp tool).
I am ok with using plastic connectors, in fact I prefer them over brass.
For cold potable water use...
Blue half inch PEX pipe for potable water
$108.95 for 300 feet
http://www.pexsupply.com/Wirsbo-Uponor-F3060500-1-2-AQUAPEX-Blue-300-ft-coil-2196000-p
For hot water use...
Red half inch PEX pipe for potable water $108.95
for 300 feet
http://www.pexsupply.com/Wirsbo-Uponor-F2060500-1-2-AQUAPEX-Red-300-ft-coil-2187000-p
http://www.supplyhouse.com/Wirsbo-Uponor-F2120500-1-2-AQUAPEX-Red-1000-ft-coil-2192000-p 35.6 cents per foot
For assorted other water use...
White half inch PEX pipe for potable water $108.95
for 300 feet
http://www.pexsupply.com/Wirsbo-Uponor-F1060500-1-2-AQUAPEX-300-ft-coil-2176000-p