Bad tasting water is a symptom with a short list of causes, and the taste itself narrows the list fast. Work out which flavor you have, whether it affects hot water only or every tap, and whether it started suddenly or crept in over months. Those three observations get most households to the cause before anyone spends money on equipment.
Match the taste to the likely cause
Swimming-pool or bleach flavor points at chlorine or chloramine disinfectant residual. Metallic or blood-like taste usually means iron, or copper picked up from your own pipework. Earthy or musty flavor often follows a seasonal algae bloom in a surface reservoir and is a nuisance rather than a hazard. Salty taste can mean sodium from a softener discharging into the drinking line, or chloride in the source. Rotten egg is sulfur, and where it shows only in hot water the water heater is the suspect.
Narrow it down before buying anything
Run the cold tap for a full minute and taste again: if the flavor fades, it is coming from stagnant water sitting in your own plumbing rather than the mains. Compare the kitchen tap with an outside spigot that bypasses the house filters and softener. Compare hot with cold. Try a different building on the same street. Each comparison rules out a whole class of cause, and it costs nothing but a few minutes.
Read the report you already have
If you are on a city supply, the utility has already measured most of this for you. Every community water system publishes an annual Consumer Confidence Report, and the EPA maintains a finder to locate the one for your address. It lists which regulated contaminants were detected and at what levels, plus the disinfectant in use, which immediately tells you whether you are tasting chlorine or chloramine. That distinction matters because they call for different carbon media.
Choosing treatment on the answer
Chlorine taste responds well to activated carbon at the point of use, and a simple under-sink or countertop unit is usually enough. Chloramine needs catalytic carbon and more contact time. Sulfur odour from a well needs oxidation and filtration on the line. A salty taste from softened water is fixed by plumbing the kitchen cold tap onto a bypass rather than by buying a filter. Match the machine to the cause and the problem stays fixed.
Questions people ask about why does water taste bad
Why does only my hot water taste bad?
The water heater is the usual source, often a reaction between the sacrificial anode rod and sulfur in the supply, which produces a rotten egg smell.
Does bad tasting water mean it is unsafe?
Not necessarily. Most taste problems are aesthetic, though a sudden change in taste is worth investigating and reporting to your utility.
Will a fridge filter fix the taste?
For chlorine taste it usually helps a lot. For sulfur, hardness or a salty taste it will do very little, since carbon does not target those.