If a taste or odor occurs at every water faucet on the property, the cause is probably the main water supply. If it occurs only in certain faucets, the problem is the fixtures or pipes supplying those specific faucets. If the problem goes away after running the water for a few minutes, the problem is somewhere in your household plumbing system.

Taste Problems:

Salty, Brackish: High Sodium
Alkali Taste: High hardness, total dissolved solids, high alkalinity
Metallic Taste: A metallic taste can be caused by inorganic chemicals such as iron (at levels over 0.004 mg/l), copper (2-5 mg/l), and zinc (4-9 mg/l) and may be related to minerals that can leach into water from pipes.

Odor/Smell Problems:

Sulfur or Rotten Egg Odor: Usually caused by bacteria growing in your sink drain or hot water heater. Sometimes this smell is caused by naturally occurring hydrogen sulfide in your water supply.
Moldy, musty, earthy, grassy, or fishy odor: Commonly caused by bacteria growing in a sink drain or from organic matter such as plants, animals, or bacteria that are naturally present in lakes and reservoirs during certain times of the year.
Chlorine, chemical or medicinal taste or odor: Usually caused by the addition of chlorine to the water, or the interaction of chlorine with a build-up of organic matter in your plumbing system.

The recommended treatment for most Taste and Odor problems is carbon filtration.