Cloudy Water

Why is my drinking water cloudy?

Once in a while, you get a glass of water that looks cloudy; maybe milky is a better term.  After a few seconds, it miraculously clears up!  The cloudiness is likely due to tiny air bubbles in the water.  Like any bubble, the air rises to the top of the water and goes into the air above, clearing up the water.  Cloudy water, also known as white water, is completely harmless.

This usually happens when it is cold outside because the solubility of air in water increases as water temperature decreases.  In the winter, water from the distribution main - which is very cold - warms up during its travel to your tap.  Some of the air that was once dissolved is no longer soluble, and comes out of solution in the form of air bubbles.

Also, water pressure has something to do with it.  Water in the distribution system is pressurized to a degree (which helps to get the water all the way from the water treatment plant to your home).  Water under pressure holds more air than water that is not pressurized.  Once the water comes out of your tap, the water is no longer under pressure, and the air comes out of solution as bubbles (similar to a carbonated soft drink).

The best thing to do with cloudy water is let it sit in an open container until the bubbles naturally disappear.


Glasses of water from a tap showing air bubbles, making the water appear cloudy.

(Credit: Massachusetts Water Resources Authority)

(Credit: U.S. Geological Survey)