Why are there bubbles in my glass of tap water?

When you draw a glass of cold water from your faucet and allow it to warm to room temperature, nitrogen and oxygen slowly come out of solution, with tiny bubbles forming and coalescing at sites of microscopic imperfections on the glass. read more

Atmospheric gases such as nitrogen and oxygen can dissolve in water. The amount of gas dissolved depends on the temperature of the water and the atmospheric pressure at the air/water interface. Colder water and higher pressure allow more gas to dissolve; conversely, warmer water and lower pressure allow less gas to dissolve. read more

There are two sources, dissolved air in and air bubbles brought in by flux of water. Water from the faucet has decent amount of pressure. The gas solubility follows Henry’s law which says the amount of air dissolved in water is proportional to the system pressure. read more

The bubbles form because air has dissolved in the water. If the tap water is cold and it warms up to room temperature as it sits on the counter, the warmer water is able to hold less gas (the amount of gas that dissolves is temperature-dependent), so the gas comes out of solution to form bubbles. read more