We used PVC in our conversion. It worked out okay, we usde insulated Adel clamps in numerous places to help keep the vibration to a minimum. If I had to do it again, I would proably use the Pex/Quest tubing and fittings, since it is much more flexible, and much easier to assemble (no gluing required, assembles with hand tools). I do think that using flexible hose would work well, too....one caution here is that some hose, such as the clear vinyl type hose (reinforced or otherwise) is not suitable for hot water or higher pressures that might be found in some RV's when hooked up to a city water line (take my word on this...I tried this as a temporary fix on a friend's house and it swelled up like a baloon and burst...quite a mess). But the Parker push-lock style hose would do real well, and would be fairly inexpensive.