Fairfax Water

Water Quality Bulletin

Explanation of Milky Water Caused by Dissolved Oxygen

During the time of year when the water coming into the house is colder than the temperature inside the house, this phenomenon can occur. Cold water holds more oxygen than warm water does, consequently when the cold water from the water mains outside comes inside our warm homes, and the water begins to warm, the oxygen has to escape. It does so by bubbling out in air bubbles which makes the water look milky. A visual example of this is to run water into a clear container and observe for a short time, as shown below. If the water clears from the bottom to the top of the container then the phenomenon described is occurring. The air bubbles are moving from the bottom to the top of the container to escape into the open atmosphere.


Dissolved Oxygen Dissipating from Cold Water to Warmer Atmosphere


The following pictures illustrate the phenomenon by time of exposure.







The appearance of dissolved oxygen in water is a natural occurrence due to the physical nature of water. This phenomenon is harmless and has no bearing on water quality. Because cold water has a higher capacity for holding dissolved oxygen and is released as the water is warmed, the occurrence may be exaggerated by aerators and water heaters.

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