Once in a while, you get a glass of water and it looks cloudy; maybe milky is a better term. After a few seconds it miraculously clears up! The cloudiness might be caused by the water in the pipes being under a bit more pressure than the water in the glass, but is more likely due to tiny air bubbles in the water. Like any bubbles, the air rises to the top of the water and goes into the air, clearing up the water. Cloudy water, also known as white water, is caused by air bubbles in the water. It is completely harmless.