The last time I worked on an executive water system I wanted to cry. Its all copper pipe (not tubing) swedged fittings and all. I think you have to take the sink cabinet completely out to access your lines. Also note that your lines run through the floor from oneside of the coach to the other. I'm not sure about the configuration of the bathroom sink in a 70 model my experience is with a 74 and 77 model.
