Does anyone recommend a good quality Pex manufacturer and supplier for in slab installation? I could also use some help with final design as initial designer has approx. 500 ft loops and from what I understand that is a bit long for in slab designs?

For most residential work most domestic and european PEX will do (oxygen barriers are a must). 1/2" PEX is the residential standard. 500' is for commercial in large tube sizes.

I design systems for a living.

500 feet is to long, 3/4 too fat,
think 1/2', 300 +- 10% as a start, this will get you on the average path,
Badgers right you will need a barrier pipe unless you have a non ferrous system, then you can use non barrier.
3/4 is a lot harder to work with for little gain unless you are running a large shop or pole building type structure. No place in a residence.

Dan

Thank you both so much. Are there any specific manufacturers of pex that are better than others? ie, more flexible or easier to install?

500 is not always too long. we do 500 in basements all the time, or in other particularly low load situations. it slows down initial startup, but if you only need 0.2 to 0.4 GPM in a loop, you can go quite a long distance with half inch pipe.

If you are using multiple or larger pumps to accomodate 500, or larger pipe, THEN it's a waste of money/energy.

for slab installs "more flexible" is less of a concern.

Not for the novice.

Can we talk about insulation under a slab... hehehehee.