It could be something in the piping, the faucet, a special attachment, or a problem with the well water. Consider the circumstances when your water turned from clear to fizzy—had you installed a new faucet or a water purifying system recently? Had your faucets been off for quite some time? Do you use well water?
First thing’s first, check all of the other faucets in your home to see if the water is fizzy throughout the house. If the water is just fizzy in the single faucet, chances are it’s the faucet fixture or a water attachment. Check to make sure you don’t have leaks in or around the faucet that would be letting air in the water. Be sure to check the hose, as it could be leaking or corroding.
If the entire house has fizzy water, it could be a bigger problem.
If your home water source is located near a gas well or a spring, consider having your water tested by a trusted plumber. Try filling a glass with water, and tossing a piece of PEZ candy or Mentos in it. If it starts to foam over, it’s more than just air in the water you’re dealing with. Another thing to consider is the scent of the water. If it has an odd odor, especially like gas, call a professional.
(Photo Credit: gehat @ Flickr)