What Causes Water to Appear Gray From the Faucet?

One of the best ways of safeguarding your home water supply is to regularly inspect the water because potentially harmful contaminants often make their presence known through discoloration or unfamiliar odors and tastes. If the water coming out of your faucets appears gray, for example, it is important to address the issue quickly to avoid putting your family at risk of exposure to contaminants.

Air in Water

Excess amounts of air in your home's water supply can given water a white, gray or milky appearance as it comes out of the faucet. To confirm whether this is the case, listen for any knocking or banging sounds in your plumbing when you use water appliances, another indication of air in the water. Another test is to pour a glass of water and let it sit in the refrigerator to see whether the air dissipates and the gray or hazy appearance goes away on its own.

Hardness Scale

Another possible reason that your water could take on a gray appearance occurs when hardness scale -- mineral deposits on plumbing equipment that result from high levels of calcium and other water hardness minerals in water -- are dislodged from plumbing equipment. If you have recently had your plumbing equipment cleaned, this possibility is all the more likely. Hardness scale will generally appear as white or gray particles in the water, so inspect the water closely to see whether the gray color is a result of small gray particles floating in the water. If water hardness scale is indeed the cause of the problem, you might need to install a residential water softener to remove the hardness minerals.


A more ominous possibility is that your water is taking on a gray color because of the presence of bacteria in the water supply. Sulfur bacteria living in water can produce a gray, white, black or reddish brown slime that is visible in water. The sulfur bacteria itself is usually not harmful in the water supply, but the presence of sulfur bacteria almost always indicates the presence of high levels of sulfur and hydrogen sulfide in your water supply, which can be harmful in high concentrations and can impart an unpleasant odor and taste to the water. If you use a water well, you can typically treat high sulfur levels with a shock chlorination treatment or an automatic chlorinator. If you use a city water supply, report the issue to the city so that they can test your water quality.


Gray colors could also be the result of fungal growth. Fungi that produce gray slime are typically not present in the water supply but are prevalent inside your home. Once they land on a damp surface such as a shower head or leaky faucet, they can produce a fungal colony that is gray or white and slimy. Water passing over this slime can assume a gray color. To confirm whether this is the case, check toilet cisterns and bowls, washing machines, taps, bathroom tiles, shower curtains and other areas for the presence of gray slime. If you find the gray slime, deep clean the area with water and a commercial disinfectant or a diluted bleach solution.