Today's question: Why does drinking water often look cloudy when first drawn from a faucet?
"Plain Talk" answer: The cloudy water could be caused by tiny air bubbles in the water similar to the gas bubbles in carbonated soft drinks. After a while, the bubbles rise to the top and are gone. This type of cloudiness occurs more often in the winter, when the drinking water is cold and holds more air, and then is drawn into the house and heated up in the plumbing.
Another cause of cloudiness in cold water comes from calcium. In certain waters, the nontoxic insoluble chemical calcium carbonate will precipitate when it is cold. Because it is white, this precipitate can cause the water to look cloudy, but the particles will settle to the bottom of the glass (usually in about 30 minutes), in contrast to the air bubbles previously discussed that rise to the top of the water fairly quickly. Water containing calcium carbonate precipitate is perfectly safe to drink or use for cooking, though it may be unappealing to the eye.
For more information on this and many other water-related topics, check out "Plain Talk About Drinking Water" by Dr. James M. Symons.