I replaced most of my old rusty galvanized pipes under the crawl space
with oversized copper pipe when prices for copper hit rock bottom just
a few years back. But, I also used pex tubing for my radiant floor
system around the same date, due to concerns about concrete/copper
chemical reactions. Pex won't collect so much calcium/magnesium on the
interior of the pipe I understand either, so for long term plumbing
like the radiant floor, I had no choice.

I found the pex to be relatively easy to work with because fewer joints
are required. The tubing can bend around wide corners, and squeaking
is a thing of the past with this material. Be careful not to pinch the
hose when bending, or a weak spot will develop. If necessary, a little
heat will make the Pex rebound to new though. I used stainless steel
hose clamps and brass fitings for connections with the pex and haven't
found any problems. Heat the Pex slightly, and it will fit over the
barbed fitings, and then when cool fits pretty tight anyway. The new
fittings probably are better, but it's not a big deal. The only
problem with Pex that I've heard of is under very high temperature
situations. If your solar water flows through at temperatures above
180F, I'd be worried about a meltdown, but I run 140F through my system
all the time without concern. Copper won't face this high temp
problem, so I'd probably use copper for solar panel and hot water
heater connections.

As for using PVC or anything related to that inside the house, I
wouldn't do it. Outside, for irrigation lines, and maybe even for the
main water line leading to the house, yes, but a burst water pipe in
the wrong place is a real expensive nightmare to be avoided at almost
any cost. PVC degrades much faster in sunlight, but it does dry out
even in the dark, and becomes brittle over time regardless, and so
shouldn't be used inside the house. I still used soft copper tubing
for a recent water main to house connection. Even though it's buried
two feet down, I still worry that seismic or shovel action could crack
PVC.

If you can afford copper it, get oversized type L pipes though. I ran
type L 1-1/2" copper cold water and 3/4" hot water copper pipes under
my crawl space. The mainfold for the radiant floor system was 2" pipe.
I don't like water softeners, and I don't want calcium build-up to be
a problem in my lifetime in the main lines of the house system. It
also helps reduce water hammer and other strange sounds...But, given
copper prices today, PEX is the way to go most everywhere, except the
garden.

Bates wrote:
I've been planning to re-plumb most of an old house we bought in my
home town for vacations, using pex products. My investigation so far
hasn't revealed much in the way of negatives about pex pipe. The Lowes
around here are stocking a good selection of Zurn brand pex pipe,
fittings and tools. BTW, Zurn now has a new tool, and new crimp rings,
so one needs only the one (expensive) tool to do 4 sizes of tubing.
The new tool is the kind that pinches an ear on the crimp ring, as
opposed to the tools that surround and squeeze the entire ring. That
means that it can be a bit smaller, and thus fit into some tighter
spaces. Ease of installation, resistance to freezing, and manifold
type of installation seem to be pluses to me. If anyone has had bad
luck with pex, I'm probably not the only one who would like to hear of
it. I'm getting ready to puchase the tools and supplies pretty soon.
Home Depot seems completely unaware of pex plumbing, and Menards home
centers do carry pex (Durapex), but perhaps not as complete a set as
that of Lowes. Thanks for any input.

Bates