Do you mean PEX-Al-PEX? It’s mostly obsolete now, in favor of “oxygen barrier” PEX. The latter is generally approved for potable use, but there’s no reason to

Do you mean PEX-Al-PEX? It’s mostly obsolete now, in favor of “oxygen barrier” PEX. The latter is generally approved for potable use, but there’s no reason to use it. It’s intended for closed-loop heating or cooling systems that contain non-stainless iron alloys, and the idea is that any oxygen initially in the water will be rapidly depleted, and deoxygenated water is not corrosive.