We get water filters to remove contaminants such as bacteria. However, some bacteria can be helpful. Many filters we use have a sand base and water travels through that sand to remove harmful germs. When we start using these bacteria grow on the sand particles and those bacteria on the sand remove bad tastes in water.
What we drink from the faucet many times has a muddy and stale odor. It is not something that affects our health, but many people will not drink water that tastes bad or dirty. Many companies continue to strive to remove the bad tastes because people think that bad taste means harmful things in the water. Water companies are always striving to change and upgrade their filters, however, they have found that maybe leaving an older system in place and adding additional filters after going through the first one may be a good choice.
The compounds that are the culprits of the bad taste are usually geosmin and methyl lisoborneol. These compounds are in water organically. When using a sand based water filter it accumulates a barrier or a type of film on the outside of the grains. When new water passes through the sand with this covering of film it attracts and removes these compounds from and eventually breaks them down.
Old pipes in your house can also cause bad taste, especially if your house has copper or a metal base which it uses for the pipes. You may notice a difference in taste from your home to a newer home. Some people think the newer home has water that actually tastes worse. This may be caused by a similar fashion as mentioned above.
So if you are using a sand type of water filter and you really want fresher tasting drinking water you may want to continue to use the old system.