Because of the obvious reasons stated above we went with PEX on our rebuild on the 64. However there are serious questions about PEX, like exposure to sun light, chlorine deterioration, leaching chemicals, etc.
Here is an article that may shed some light on the subject.
How Safe is PEX Tubing? | GreenBuildingAdvisor.com
Weighing the pros and cons
"As with most building materials today, it's not easy to determine the relative merits of copper and PEX for domestic water supply," writes Robert Riversong. "There are significant benefits and liabilities, including deleterious health impacts of both."
Here's a paraphrase of Riversong's advice: Copper should be soldered with lead-free solder, but soldering flux is not only toxic but also corrosive to copper. Copper is vulnerable to corrosion and pin hole leaks. Water turbulence in copper lines can increase the amount of dissolved lead and copper in the water, especially when the pH is less than 6.5.
When acidic or soft water sits in the line for more than six hours, the line should be flushed for up to 60 seconds before the water is used for drinking or cooking. And in these conditions, hot water should never be used for cooking or drinking.
PEX, on the other hand, is resistant to acids, better at resisting freezing damage, and doesn't scale or corrode. It's been used in Europe since the 1960s, and even "plastic-phobic" California embraced PEX.
One Achilles' heel with PEX, Riversong reports, it is chlorine resistance. "Even short-term exposure to sunlight can dramatically reduce the resistance of PEX to chlorine and result in premature rupture of the pipe," he writes. "Studies show just a one-week exposure to sunlight may reduce the chlorine resistance lifetime of some PEX pipes by half; with a two week exposure completely depleting PEX of any chlorine resistance.
"California’s January 2009 approval of PEX relies upon the less-protective PEX chlorine resistance standard ASTM F2023, instead of the much superior NSF P171 standard," he says. "ASTM F2023 only assures an adjusted lifetime of 25 years, while the NSF P171 standard assures a 40 year adjusted lifetime."
PEX can't be melted and resued, an environmental drawback, and it produces toxic smoke when it burns. More troubling, the California lawsuit alleged PEX could indeed leach certain chemicals, including methyl tertiary-butyl ether (the MTBE referred to in the original post) along with ETBE, a related chemical, Riversong says.
- See more at: How Safe is PEX Tubing? | GreenBuildingAdvisor.com