Bad tasting tap water is usually one of five distinct complaints, and each has a different cause and a different fix. Buying a filter before working out which one you have is how households end up with an expensive unit that changed nothing, so the useful first step is putting a name to the taste rather than to the product.
Chlorine, swimming pool, chemical
The most common complaint on a municipal supply, and the most easily solved. It is the disinfectant residual doing its job all the way to your tap. Carbon removes it, from a pitcher upwards, and the taste often clears simply by leaving a jug in the fridge for a few hours. If the taste is more medicinal than pool like, the utility may be dosing chloramine rather than free chlorine, which needs catalytic carbon. The EPA requires every community water system to publish an annual Consumer Confidence Report naming the disinfectant, and maintains a finder for them.
Metallic, bitter, or like coins
Usually metal actually in the water. Iron gives a metallic taste alongside orange staining. Copper, from acidic water corroding your own pipework, tastes metallic to bitter and comes with blue green stains, and that one deserves prompt attention because the corrosion is progressive. Zinc from galvanized pipe gives a similar character. A first draw that tastes metallic and clears after running the tap points firmly at the plumbing rather than the supply, and a metallic taste with no visible staining can also be a low pH problem.
Earthy, musty, fishy or rotten egg
Earthy and musty tastes are usually harmless organic compounds produced by algae in a surface water source, most common in warm months, and carbon handles them well. Fishy is often the same family of compounds. Rotten egg is hydrogen sulfide: on a well it comes from the aquifer and needs oxidation and filtration, while on hot water only it is generally the water heater anode reacting with sulfate, which is a heater matter rather than a water treatment one. Which taps carry the smell is the diagnostic.
Flat, salty, or sweet
Flat water is water with very little dissolved in it, typically after reverse osmosis or distillation, and it is fixed by remineralizing rather than by filtering further. Salty suggests elevated sodium or chloride, from a softener discharging incorrectly, from road salt reaching a shallow well, or from saline intrusion in coastal areas. Sweet is normally elevated alkalinity or a particular mineral balance and is harmless. Our water softener guide covers the sodium question, which is the one people most often want addressed.
Questions people ask about why does tap water taste bad
Water tastes of chlorine, what fixes it?
Carbon filtration, from a pitcher upwards, or simply refrigerating a jug for a few hours. Chloramine needs catalytic carbon rather than standard.
What does a metallic taste mean?
Metal in the water: iron from the supply, or copper or zinc from your own pipework. Blue green staining alongside it points at acidic water.
Rotten egg smell on the hot tap only?
Usually the water heater anode reacting with sulfate rather than a supply problem. Which taps carry the smell is the key diagnostic.
Why does filtered water taste flat?
Reverse osmosis and distillation remove the minerals that give water its character. A remineralizing cartridge restores the taste.