The Tuolumne River water piped from Yosemite National Park to San Francisco taps and toilets is some of the best municipal water in the world, the San Francisco Public Utilities Commission is proud to boast. Yet our imported Sierra snowmelt is not a perfectly healthy flow for everyone.
San Francisco's H20 is chemically treated with chloramine and radiated with ultraviolet light before it hits local pipes, but unlike other city water supplies — such as the East Bay Municipal Utility District water in Oakland — our water is not filtered, which means run through a screen to remove impurities, just like that empty Brita pitcher in your fridge but on a larger scale.
Spreck Rosekrans, an environmentalist and water expert, reports that during San Francisco's process certain microorganisms, such as the protozoans that cause giardia and cryptosporidiosis, are not entirely killed off. The water is perfectly healthy for most of us, but not necessarily for those with HIV, AIDS, or weakened immune systems. This is partially why the LGBT Center on Market Street has filtered its drinking water since it opened its doors in 2002, according to David Gonzalez, the center's HIV services manager.
Unfiltered public water may someday run afoul of the Environmental Protection Agency, which could require San Francisco to filter its water, Rosekrans says. In the meantime, it isn't good enough for Virgin America, which filters the tap water available for passengers at San Francisco International Airport's new terminal, where there are reusable bottle "filling stations" (i.e., taps) — and it's also not quite good enough for certain offices at City Hall, where the water is also filtered, according to building manager Rob Reiter. This isn't from a public health concern — bureaucrats have been publicly extolled to ditch bottled water and drink the tap water, not avoid it. Rather, it's because of the building's old pipes, which (in the words of one city worker) imbue a certain "green tea-like tinge" to the water from City Hall sinks. Offices with new copper plumbing, installed during a 1990s retrofit, don't have this problem, but rooms stuck with the original plumbing have filtered water available from water coolers, Reiter says.
There's still some controversy as to exactly how much cleaner the filtered water is. The science linking waterborne microbial infections in people with low white blood cell counts is only "initial research findings" and not conclusive, according to the Gonzalez, who notes that the LGBT Center is evaluating whether it needs to continue filtering.
As for City Hall, Reiter says "The PUC does an excellent job of filtering out impurities for the most part. But folks here do like to know they're getting the purest water possible."
That, of course, means purer than what the rest of us get.