. My main reason for using stainless valves,bulkhead etc over brass is due to being able to break apart and soak the **** outta the parts without fear and rinse them clean its more the disolution of oxides(****) off the copper by the mildly acicdic wort than anything .If ya chiller dosent have green/blue crystals growing on it and isnt black with oxides,then ya fine...dont fear clean copper in the boil. I find if you strip ya fittings down after every brew,and there stainless,a good percarbonate soak ,brief scrub with a soft bristled sorta brush,rinse,air/sun dry and there ready for reasembly/clean as a whistle for ya next brew.