First, you have two general choices:
- a simple filter system that traps particles and/or chemicals, or
- a more expensive and larger Reverse Osmosis system that produces exceptionally clean and pure water.
If your water issue is chlorinated city water that you want to simply remove the chlorine from, a two stage filter would be adequate - a charcoal filter with a prefilter in front of it. These are commonly available online at Amazon or other sites and at your local stores like WalMart or Lowes.
A higher level of purity can be had with a Reverse Osmosis system. These are usually either 4 or 5 stage with an expensive and fragile membrane that lets water pass but stops critters such as bacteria and large viruses.
- Reverse Osmosis systems deliver very pure and tasteless water but wastes several times as much water as they produce because they must flush the membrane to remove contaminants.
- My personal favorite is the APEC though there are other good ones on the market.
Before you buy any brand of water filter, read the reviews. If you are on a well, the issues become more complex so please respond if this is the case with more details about your particular issues.
For more information:
Read "Can you recommend a whole-house water filtration system?" a Q&A answered by Tammy Schwolsky.