Cloudy Tap Water

Very often drinking water that comes from a municipal water supply or well may appear cloudy when it runs from the tap or faucet. This is usually most noticeable when you pour yourself a glass of water – the water takes on a milky appearance in the glass, which gradually clears when left to stand for a few minutes.

Cloudy tap water is most commonly caused by the presence of dissolved oxygen in the water. There are a number of things that can cause excess oxygen: changes in water temperature; changes in pressure; or air entering pipes after mains are shut off for maintenance work.

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Cold water is able to hold more oxygen than warm water, and so oxygen readily dissolves in cold water; but very often, it may be warmed up as it stands in pipes and household plumbing, reducing the ability of the water to hold oxygen. This is particularly apparent during springtime, when there is a noticeable change in air and water temperatures. While the water is confined within the pipes, there is nowhere for this surplus oxygen to escape to, so this oxygen effectively remains  in a supersaturated state, under high pressure. As soon as you open the faucet , you release the pressure of the surplus oxygen that has built up in the pipes. The cloudy appearance is caused by millions of tiny air bubbles escaping , which can pretty much be compared to opening a bottle of soda that releases a hiss of bubbles as you pour your favorite fizzy drink into a glass.

If your water is shut off due to maintenance work on the water pipes – either by the municipality or by your plumber – air may enter the system. When it is turned back on, the water pressure is restored, forcing any oxygen within the pipes to become dissolved in the water within the pipes. When you open your household tap, you effectively release the pressure once again, allowing the oxygen trapped within the water to escape freely.

Cloudy tap water can also be caused by high levels of calcium. If the cloudy water in the glass takes longer than a few minutes to clear, calcium may be the cause. Leave the glass of water to stand for half an hour, and if you notice a whitish sediment at the bottom of the glass, this is most likely to be calcium sediments – a result of municipal treatment processes.

Calcium is added to municipal water to reduce it corrosiveness; this not only lengthens the life of both municipal and private plumbing and fittings, but also prevents leaching of metals, such as copper, iron, and lead, from pipes and plumbing. Some of these metals can pose health risks and other problems when dissolved in household drinking water. Usually the calcium added by municipalities goes unnoticed as the sediments settle to the bottom of the large main pipes. However, if there is a sudden surge of water through the pipes, due to a burst water main, fire fighting activity, or a tanker truck filling up at a fire hydrant, these calcium sediments may be agitated due to the increased water velocity flowing through the mains, and be drawn into your household drinking water and produce cloudy tap water.

While cloudy water from your tap or faucet can be rather unappealing as far as drinking water goes, if it is caused by the presence of oxygen or calcium, it is perfectly safe to drink.

Additional Resources

Why Does Your Drinking Water Look Cloudy


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