[arcticdude]

The AH unit on mine (also a 431-12) uses pex with crimp fittings for the zones. No leaks yet. I would highly recommend the pex. I've done 2 garages and a pump house now with pex and it works very well. There is a definite learning curve, but it works flawlessly otherwise.

As I've also replaced my unit due to freeze damage, I would say the pex is very forgiving. I have not had to repair any union yet.