10-4. There’s just no place where I have seen a grey line hook up to a copper supply line.@Gunbuffer: Please read my last post. Some of these suggestions will create havoc if that copper line has a leak.
I used to make a living fixing other people’s f ups so my desire to make for a nice OCD friendly under sink vanity was strong. Also don’t like butylplastic compression fittings on both sides of a shutoff valve.
I have a feeling what happened is that copper stub got damaged or cut too short so someone ran that gray line to the nearby toilet on the same wall