In the heart of Napa Valley, St. Helena is home to world-class Cabernet Sauvignon, a historic stone-and-brick downtown and, to locals at least, brown tap water. … The problem is that naturally occurring minerals, mostly iron and manganese, have built up in the city’s aging pipes. … City officials have insisted the water may seem unappealing at times, but it is not harmful and is safe to drink. The city’s reassurances have not satisfied some residents who argue they can’t be expected to consume or bathe in brown water — while still paying some of the Bay Area’s highest water bills.