Building his “forever house,” Dean Sandbo is mulling what type of tubing to use for his plumbing supply lines. He has narrowed the choice to one of two types of cross-linked polyethylene (PEX): PEX-A or PEX-B.
Key issues, Sandbo notes in his Q&A post at GBA, are how long the tubing will last, and whether there are safety concerns — that is, will the PEX tubing leach chemicals into his drinking water?
“I am on a well,” he writes. “Any input as to the longevity and safety of these two different types of pipes?”
Although that’s where the discussion starts, GBA readers quickly turn to another potential issue: What’s the best way of achieving a leak-free connection between tubing and fittings?
That’s the topic for this Q&A Spotlight.
Characteristics vary by type
There are actually three types of PEX, as a reference article supplied by GBA senior editor Martin Holladay explains (see the “Related articles” sidebar below). Types A, B, and C are manufactured differently, which affects characteristics such as flexibility, resistance to chlorine and oxidation, coil memory, and cost. The lettered designations aren’t grades, just references to the manufacturing process.
For Richard McGrath, PEX-A is at the top of the heap. “PEX-A is produced with a better manufacturing process than PEX-B as the crosslinking takes place during the extrusion process,” McGrath writes. “PEX-A products usually achieve an 85% crosslinking while PEX-B products average a 65-70%.”
PEX-A is more resistant to the chemicals commonly found in plumbing and heating systems than what it has replaced, he adds, and long-term testing by Uponor, one of the manufacturers of PEX-A, is very encouraging. The company holds an unofficial record for resisting high temperature and pressure, McGrath says, holding up to 175 pounds per…