@jerzone most of house is PEX A. it transitions to copper in annoying places. under my sink, the shutoff valves have failed completely so i’m replacing the stub of copper+valves with PEX->PEX. first time doing this myself though, so i’ll let you know if it’s a disaster. but PEX A seems pretty foolproof - if it’s physically connected, it’s sealed. joints just continue getting tighter over time.