Bobby,
I think the RV hoses are actually a plastic of some kind and technically not really rubber. When they are brand new the RV potable water hoses may give off some minor amounts of something you can detect, but after running some water through them I can't taste or smell anything. These hoses are commonly used by almost all of my brewing friends and I haven't heard anyone mention a problem with them. I've been using them for a long time without issues on both sides of the carbon cannister filter. Most of us expose our water and beer to a lot of plastic in the brewing process. It's difficult to avoid plastic exposure entirely with the cooler mash tuns, vinyl hoses, plastic spoons, racking canes, plastic fermentation buckets etc., etc. Yes, the potable water hoses are supposed to be certified "safe", although I would think the manufacturers would also tend to design them so that they don't affect the flavor of the water also. Seems if there was a problem due to the hoses that it would surface in competitions. So far, for me, it hasn't been an issue.