In a part of the world notoriously wary of the ill-effects of alcohol and caffeine, it is not too surprising, perhaps, that people like their water out of bottles. But this is not just about fads or dietary preferences. It borders on paranoia: offer a glass of tap water and you will not just get a polite refusal, you will get a lecture.
"How can you drink it? It tastes awful," said one of our neighbours. "It is full of industrial effluent and you're poisoning your children with it," said another. "You can't drink the water because the municipal pipes are full of lead and give you Alzheimer's disease," said yet another.
All this is very puzzling, since the Metropolitan Water District (MWD), which covers the six counties of southern California, actually has some of the cleanest, and tastiest, water in the country. In a competition between different public water supplies last year, it came out number one in a blind tasting test. Its quality is tested hundreds of thousands of times a year. But nobody seems to know this.
Affluent Californians drink bottled water because they think it is healthier and they prefer the neutral taste. Poor Californians drink bottled water because many are first or second-generation immigrants brought up in cultures - Latin American, especially - that say you would be crazy to trust the municipal authorities to keep the water clean.
The result is that everyone spends a small fortune each week on bottles or giant coolers from one of the thriving private water concerns.
The bigger companies offer to deliver water to your door, and their salesmen spend considerable energy canvassing the unconverted in suburban neighbourhoods. Thus was I buttonholed by a man from Sparklett's, one of the most successful private companies, not least because its agents have a reputation for catching and overpowering daytime criminals.
I almost overwhelmed him with the news that I drank out of the tap. "You can't do that," he exclaimed. "Tap water contains a deadly bacteria called crypto." Crypto, it turns out, is short for cryptosporidium, a genuinely unpleasant bug derived from animal faeces that can get washed into reservoirs. In Wisconsin a few years ago, an estimated 100,000 people became sick in a cryptosporidium outbreak. But southern California has never suffered from it.
There are more grounds for concern from industrial effluent. Trichloroethylene, a potent factory cleanser, seeped into the groundwater of the San Fernando Valley at an alarming rate in the late Eighties, forcing a costly clean- up.
More recently, a chemical called MTBE, which is added to petrol to make it burn more cleanly, was found to be leaking into aquifers. Ammonium perchlorate, a rocket fuel component that can cause thyroid problems and cancer, has recently been discovered in Sacramento and in parts of southern California.
But even in these cases the risk to public health has been far lower than the scaremongers have suggested. The ammonium perchlorate, for example, was found to exceed the provisional "maximum contaminant level" of 18 parts per billion. But this level was deliberately set extremely low. It takes at least 3,000 parts per billion to trigger thyroid problems, and 200,000 parts per billion to induce risk of cancer.
Water is a sensitive subject in California at the best of times - Los Angeles stole most of its supply from upstate farmlands at the beginning of the century - and big private interests have often been happy to distort the issues. Discrediting the public water authorities is a time- honoured ploy of property developers seeking to minimise the effects their projects will have on groundwater levels.
That helps to explain why the bottling companies find customers so easily. "They feed on the public's phobias," said Lynne Plambeck, an environmentalist and former water board official. "They are not required to do the testing that public water agencies are and are undoubtedly not as safe. But in a town that pays big bucks for a grande cafe latte, is it any wonder we want to buy water as well?"Reuse content