How to Choose a Water Filtration System

Filtration systems remove impurities from tap water. The most common use carbon or reverse-osmosis filtration. Look for certification by NSF International, which establishes the standards.

  1. Have your water tested so you know how much and what kind of filtration you need (see "eHow to Test Water Purity').
  2. Decide whether you want a faucet-mounted system, which is inexpensive and easy to install but requires frequent filter changes, or an in-line system, which mounts directly to your plumbing system. The latter is more costly but more comprehensive, and requires only occasional filter changes.
  3. Look into an NSF-certified carbon filter for either system if your test comes back with chlorine, chloroform, pesticides or organic chemicals. Carbon filters are not effective against lead or other heavy metals, flouride, chloroform, or some microbial contaminants.
  4. Think about getting an in-line reverse-osmosis filtering system if your water test shows sodium, ferrous iron, nitrates, lead, fluoride or organic contaminants. Be aware that a reverse-osmosis system puts out a limited amount of drinking water and wastes a lot of water (about 4 gallons of wasted water per gallon of clear water). If your water's calcium count is high, you'll need to use a water softener with this system (see "eHow to Eliminate Hard Water').
  5. Consider a system with a cutoff meter (also known as a performance indication device) that lets you know when it's time to change the filter.

Things You Will Need

  • Home Water-quality Test Kits
  • Water Filters
  • Plumbers


  • Install a sediment filter ahead of the carbon filter to remove solids that will clog the carbon.
  • Read product claims for removal and choose a system designed to treat your water conditions.
  • To obtain further information on water filtration, contact NSF International at www.nsf.org or call (800) NSF-MARK.


  • None of these filter types will solve hard-water problems.

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