mmm I think yer bud is blowin smoke - it's possible the 'staining' is from over flows, but most likely from leaks under pressure, I'd take it to the shop and have them pressure test it and get their advice .... and skip the vinegar, it's extremely corrosive, it's not "CLR kitchen cleaner" - you could do as well to clean it off with a scrub brush and garden hose, but I'd count on it coming back in time
Bill
