I recently bought a by-pass kit from an RV dealership to install on the hot water tank of my 1984 H-31. The kit as well as the 6 feet of new tubing I bought are 1/2 inch as is the existing fresh water supply line to the hot water heater, however, all the rest of my fresh water system is grey in color and a bit smaller than the new stuff. A friend who has a CS 30 of about the same vintage as my boat tells me he had the same stuff and could not find fittings for it so he replaced the whole thing. I think the old grey stuff has NPT threads because one screws directly onto the hot water exit line from the water heater. Has anyone had any luck adapting the new half inch stuff to the old greay stuff? If I can't adapt it I will have to replace my whole system. Thanks. Reg