According to Gary Slusser :
"Chris Lewis" wrote
According to Gary Slusser :

PEX is not harmed by freezing.

Their metal fittings may be.

Plastic plumbing (ie: all plastic irrigation systems) is a lot more
forgiving of freezing than copper or iron because it stretches somewhat.

In any type of plumbing, if the tubing expands as the water freezes, the
pressure is relieved, thereby the fittings don't break.

PE expands much more than other plastics, such as PVC, but PEX is able to
expand (its ID) more than any other type of water plumbing material without
failure. It has been tested to many thousands of expansions without failure.
Some is expanded to make its connections as opposed to crimped connections.
Heating it allows it to restore to its original shape, such as when a piece
has been kinked. This is from tech sheets and installation guides. Where do
you get your info from?

My own plumbing...

I just had a short copper segment (about 3") on a PE line rupture (missed
draining part of a irrigation line segment feeding a hose bib).

As long as the water stays liquid during expansion, then, of course plastic
pipe expansion will prevent rigid metal connectors from rupturing.

But it doesn't stay liquid during expansion.

The expansion of water during freezing takes place from the minima volume
(@4 degrees C) down and _during_ crystalization.

Much of the expansion therefore takes place while the water can't flow,
because it's at least partially "locked in place". Whether it'll
rupture the fitting depends on a lot of factors (ie: fitting length,
freeze rate, line diameter, where in the pipe it starts freezing, etc).
It won't necessarily rupture on the first cycle either (but it was the first
season for the fitting I just mentioned :-(.

Freezing lines, any lines, no matter what they're made of should be avoided.

Plastic pipe installations will certainly perform _better_ than rigid metal
pipe in the face of freezing. But repeated freeze cycling is to be
avoided especially when there's highly rigid parts in the system (metal
connectors and fittings, "device" housings - ie: pumps, whether metal
or plastic).

And as I said, the choice of the material for potable water lines should be
dictated but the water quality and since plastics are totally inert.... what
to use should be a no brainer... well for those that are aware of water
quality and metal tubing problem issues anyway.

Do you have a reference somewhere to the comment about "copper toxicity"
in plumbing?

I should also point out that plastics aren't entirely inert, as the PB
plumbing class lawsuit proved...

Don't get me wrong, I use plastic pipe whenever appropriate myself. But
pros-cons aren't entirely one-sided.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.