Dumping garbage and industrial waste into rivers and lakes in China is an everyday affair, Rick. It happens all across the country and has been well documented. If you have evidence that Chengdu’s water is clean, please present what you have.
In the summer of 2011, the government reported that 43% of state-monitored rivers are so polluted that they’re unsuitable for human contact. A study by China’s EPA found that water pollution levels were twice what the government predicted because they didn’t include agricultural waste. About two thirds of China’s population (500 million people) use water contaminated by human and industrial waste.
If you want to drink the tap water, suit yourself. Personally, I think that is nuts. If I had a choice, I wouldn’t breathe the air, either.