Professional water testing is fairly expensive, so it should not be undertaken lightly, but it is also important for determining what kind of water filter you need to keep yourself and your family safe, healthy, and drinking clean, pure water. Casual, light duty filters are appropriate for water that is already clean or nearly so. On the other hand, heavy duty filters may be needed for highly contaminated water, or specialized filters can help if unusual pollutants such as arsenic are present in higher than normal quantities.  

There is no point in buying a water filter system that is more complex than you need. Overkill is usually expensive. However, buying too weak a water filter is equally problematic, if not more so, since the harm will then be done to your body rather than just to your wallet. Money is ultimately replaceable, but, unfortunately, health is not.

    Situations where having your water tested professionally is a good idea include:

• If your tap water smells bad, tastes bad, or is visibly cloudy, then you should have it tested posthaste. These conditions all indicate that some contaminant is present in your water, and while it may be no more than a bit of bad-tasting silt, it could also be sewage, overflow from a factory, pesticides or fertilizers from nearby farms, or any of a host of other perils.
• If you have your own well, you should have the water tested annually. Having it tested more often is recommended if your well is shallow or particularly exposed to runoff.
• If your well is located somewhere that exposes it to contamination, such as near a large barn full of livestock, have your water tested quarterly if possible.
• If any information you receive leads you to believe that dangerous compounds such as arsenic, industrial solvents, or lead from old piping systems is present in your water, a good test is mandatory for safety.
• If you notice health effects from drinking your water, such as a burning sensation in the mouth, diarrhea or loose stools after consuming it, upset stomach, or rashes on your skin after bathing in the water, an immediate test is certainly appropriate.
• Water testing is also appropriate if a new business enterprise is opened nearby. For example, if a company starts “fracking” for natural gas near your home, a large factory farm or power plant opens nearby, or any other activity that might affect the long-standing balance of the local water table begins, test immediately and in 2 to 3 months to see whether water quality is being significantly affected.