How To Select The Best Drinking Water Filtration System
Or Other Water Purification Method

STEP 1
Become informed
about the contaminants that are in your drinking water.

There are really only two ways to know what is in your drinking water:
Read the annual water quality report from your water company if you live in the United
     States and are on municipal water.  Your water company is required by federal law to
     make available reports listing the measured levels of the most common and/or harmful
     water contaminants.  Read a very detailed description of water quality reports.

    Your water company is also required by federal law to deliver  water to your home which
    contains contaminant amounts that are lower than the EPA maximum contaminant levels
    (MCLs).   

Test your water.  If you have a private water source (well, spring, or surface water)
     you are completely responsible for the safety of your home's water supply.
     This includes testing and then treating the water if needed, and maintenance of the
      well, pump, and pipes. 

There Are Three Types Of Drinking Water Contaminants:
   
   
   
Fortunately, most people on municipal water do NOT have a
    lot of harmful contaminants in their drinking water!
If your water is treated and distributed by a water company, it will
    probably contain:
   (chlorine and/or chloramine).
   (which include the trihalomethanes like chloroform).  
If your home is less than 5 years old, or has lead pipes (or copper pipes with lead
    solder), or has  faucets or fittings of brass, or your water is naturally soft or acidic,
    or corrosive, a possible and serious drinking water contaminant would be:
    This page contains additional information about lead.
If you live in an agricultural region,  potential harmful contaminants include:
  
  

Young infants or children, women who are pregnant, the elderly,
    and people with compromised immune systems are at higher risk
    from many drinking water contaminates!  Read about these risks.

There are many thousands of potential contaminants, both natural and synthetic.  A list and description of some of the more common and/or harmful contaminants that can be found in drinking water can be  Found Here. 

The lists of contaminants on this page does not mean that all drinking water contains them.  Fortunately, any given water supply will probably contain just a few (if any) harmful contaminants, but it is important to have an idea which ones before purchasing a water treatment solution.

Water Problem Table
Identify Common Water Contaminants by Their Sensory Clues
Important Introduction

STEP 2
Become knowledgeable
about the benefits and limitations, of the POU water treatment methods.

There are thousands of brands of POU drinking water treatment systems from hundreds
of manufacturers.  You see them in shopping malls, discount stores, hardware stores, and
mail order catalogues - and, of course, on the internet.  Prices range from around $20 to thousands of dollars.  

There are only 4 - 5 main (POU) home drinking water treatment and purification technologies, each with its strengths, limitations, and associated costs.  Some treatment units use several technologies combined.  Pop-up descriptions of each of the water treatment methods are available by clicking on the link (if Java is enabled).  To save time, if you plan to read descriptions for  more than just one treatment type, leave the pop-up window open, click back on this page, and click on another treatment method.

If you want to read through all the treatment descriptions and limitations at once (or if Java is turned off), you can find a full description here.

Ion Exchange (Not usually a POU solution.  Included because water softeners are so common)

Bottled Water is also available from a staggering number of companies that produce
    a vast range of products including:
    Distilled Water
    Natural Spring Water (including Artesian)
    Mineral Water
    Well/Ground Water
    Purified Water
    Sparkling Water (Contains CO₂)
    Flavored/Sports/Vitamin Water
    "Altered" Water (oxygenated, magnetic, vortex, and clustered water to name a few).  
  More than a few brands are simply filtered tap water.  Some bottled water is untreated, but most
    companies use one or more of the treatment methods above to purify the water before bottling.

STEP 3
Learn which contaminants are reduced
by the main Point Of Use (POU) water treatment methods.
(Selecting inappropriate technologies can result in inadequate purification and/or spending too much money)

 The table below lists only those contaminants commonly found in municipal drinking water.
A much more complete water treatment table can be found here for those who need it.

The extensive list of qualifications (Ev, Evg, E, Add, etc.)  in the table below is a reflection
of the fact that each water treatment technology has its strengths and weaknesses.
There is no single, best drinking water treatment method for every situation.

Also, extremely important:  The same technologies from different manufacturers can
have very different contaminant reduction capabilities - certification is important!

Effectiveness Of Water Treatment Method

Contaminant    harmful contaminant      * harmful at high levels

Inorganics

Disinfection Chemicals

chlorine

Ev

Ev

Ev

-

Er

E

-

-

E

Add

-

-

-

Eb

Eb

chloramine

Edv

Edv

-

-

Er

E

-

-

S

Add

-

-

-

Eb

Eb

Positive Ions

copper *+

-

-

-

-

Er

E

-

-

Con

-

S

-

-

Eb

Eb

calcium

-

-

-

-

Er

E

-

-

Con

-

E

-

-

Eb

Eb

magnesium

-

-

-

-

Er

E

-

-

Con

-

E

-

-

Eb

Eb

lead +

Edv

Edv

Es

-

Er

E

-

-

Con

-

S

-

-

Eb

Eb

Negative Ions

nitrite & nitrate =

-

-

-

-

Er

E

-

-

Con

-

-

E

-

Eb

Eb

fluoride *

-

-

-

-

Er

E

-

-

Con

-

-

-

E

Eb

Eb

Organic Compounds

Disinfection Byproducts

trihalomethanes

Edv

Edv

-

-

S

-

-

Etc

E

Cr

-

-

-

Eb

Eb

haloacetic acids

Edv

Edv

-

-

S

-

-

Etc

E

Cr

-

-

-

Eb

Eb

Pesticides =

Edv

Edv

-

-

Er

E

-

Etc

Con

-

-

-

-

Eb

Eb

Approximate price   per gallon

$0.04 to $0.10

$0.01 to $0.25

$0.01 to $0.06

$0.01 to $0.04

$0.10 to $0.20

$0.25 to $0.35

L.T. $0.01

L.T. $0.01

L.T. $0.01

L.T. $0.01

L.T. $0.01

L.T. $0.01

$0.02 to $0.04

$0.25 to $1.50

$1.00 to $6.00

Contaminant   harmful contaminant      * harmful at high levels     A more detailed treatment table

Key	Description
-	Not effective or not recommended for reducing the level of a contaminant.
E	Effective at reducing the contaminant level.
Eb	Effective - bottled water quality is entirely dependent on the quality of the company producing  it.  At  minimum, it must meet quality requirements that are equivalent to those for tap water.
Edv	Effectiveness at reducing the contaminant level depends on design & volume of the filter media.
Edis	Effectiveness at reducing the contaminant level depends on the effectiveness of the distiller design - the design needs to include a a good trap for VOCs
Evg	Effectiveness at reducing the contaminant level depends on the volume of the filter media & the  limitations of granular activated carbon, which include channeling of water around the granules.
Er	Effectiveness at reducing the contaminant levels depends on the characteristics of the reverse  osmosis membranes, the specific contaminants in the water and their concentrations, and the  water pressure.
Ev	Effectiveness at reducing the contaminant level depends on the volume of the filter media.   A filter with a larger volume of filter media will reduce contaminants better than smaller filters.
Etc	Effective - Ozone treatment oxidizes many organic chemicals and transforms them into smaller  molecules,  creating nontoxic or toxic byproducts depending, in part, on ozone exposure and the  the original organic compounds.
Es	Treatment produces a sediment/deposit that needs to be filtered or backwashed.
S	Somewhat effective at reducing the contaminant level.
Sro	Somewhat effective at reducing the contaminant level.  The reverse osmosis system must have a  good activated carbon filter attached to reduce the levels of some organics.
Con	Contaminant can be concentrated by the treatment method.
Add	Specific contaminant added to the water by the treatment method.
Cr	Treatment method creates new contaminants in the water.
+	Lead and copper are not frequently in water that leaves the municipal water treatment plant.  If  the water is corrosive, minerals (frequently lead and copper) can leach out of a home's plumbing  and fixtures.
=	Nitrites, Nitrates, and Pesticides are not typically in municipal water.  These compounds are  regulated by the EPA, and if the water company is in compliance the levels should be below the  EPA's MCL.  There will probably always be some companies, however, that are out of  compliance, particularly in heavily agricultural regions.  The water quality report should have  information about whether these contaminants are a problem in your water.
^	There are many specific organic chemicals in each of these categories, many harmful, many not.  The Key simply indicates treatment methods that are listed in the literature as effective against  representative compounds or stated as a treatment method of choice.  Check with the specific  manufacturer (or certification organization) about specific contaminant removal.
*	Cation exchange - Water softeners use cation exchange to replace positive calcium and   magnesium ions with a different ion (usually sodium) that does not cause the problems of mineral deposits and other nuisances.
The table and descriptions above provide a good overview of the benefits and limitations of the treatment methods for simple water problems, but a far more extensive discussion of these issues can be found here.

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My recommendations for a POU water treatment solution:
About Me

The most important consideration for selecting a water treatment solution is that the
    treatment method effectively reduces the contaminants of concern in your water.  

Always check the manufacturer's certified contaminant reduction table to make
    certain any treatment method you are considering will significantly reduce the
    specific contaminants you are concerned about!

The suggestions below are in order of my preference   The criteria I use for ranking the methods are ~ 
    the best performance (the product effectively reduces contaminants of concern), 
    at the lowest price (initial + ongoing costs), 
    with the least maintenance, 
    for the longest life.

1) Solid Block Activated Carbon (SBAC) filtration system - A high quality
    SBAC water filter will provide decades of service for a treatment cost of typically
    under $0.10 per gallon, minimal maintenance (a periodic cartridge change), and no
    electricity use.  Recommended highly if your water treatment needs are met by the
    characteristics of these filters.  Go directly to this page for details and ordering
    information on an excellent value SBAC filter.  Take advantage of several
    special offers.

2) Reverse Osmosis - Recommended in situations where the water contains
    contaminants of concern, like nitrates, salinity, and/or those heavy metals that can
    not be reduced by activated carbon.  A high quality activated carbon filter should
    be part of the package to reduce organic compounds not removed by RO.  The
    cost per gallon is about double SBAC, and there is somewhat more maintenance
    involved. Electricity is not ordinarily required for proper functioning, but relatively
    high water pressure is.  Details on a good RO system with an excellent SBAC post
    filter can be found here.

3) Distillation - Recommended in situations where the water contains contaminants
    of concern, like nitrates, salinity, and/or heavy metals that can not be reduced by
    activated carbon.  Distillation is an excellent, highly effective water treatment solution
    for "really ugly" water.  The reason I do not highly recommend it is because
    distillation is typically around twice as expensive as RO (about 4 times more
    expensive than SBAC), and most systems require electricity to operate - when the
    power is out they are completely useless.

Quick summary of other water treatment methods -
                                              A complete description can be found here

A) UV - Not recommended as a single, stand-alone water treatment solution because
     it is only for killing biological contaminants and does not reduce other harmful
     contaminants that might be in the water.  A good option, however, to provide
     additional protection for water filtered by a good activated carbon or RO filtration
     system to kill bacteria and viruses that may make it through the filters.

B) Bottled Water - Usually a good choice for safe water, excellent for emergencies,
     but most is very expensive compared with other alternatives ($0.25 - $6.00 per
     gallon).

C) Granular Activated Carbon (GAC) counter-top our under-counter filters -
     Usually better than nothing if manufacturer recommendations are followed.  Large
     pore size and granular nature of the filter media make them less effective at
     contaminant removal than a SBAC filter.  They are, however, usually much less
     expensive than SBAC systems.

D) Faucet- Mount Filters - (Can be SBAC or GAC) - SBAC faucet-mount filters
     typically have a pore size of about 1 micron - able to effectively reduce cysts.  They
     are smaller than most counter-top or under-counter SBAC filters and therefore not
     as effective for contaminant reduction at the same flow rates.  GAC faucet-mount
     filters have essentially the same effectiveness as Pitcher Filters.  Both kinds have
     relatively expensive replacement cartridges do not last very long.

E) Pitcher Filters - Better than nothing and most will reduce chlorine and sometimes
     lead to acceptable levels.  Large pore size and relatively small amounts of granular
     media make them ineffective for effectively reducing the levels of many
     contaminants.  Relatively expensive replacement cartridges do not last very long.

F) Water Softeners - Reduce hardness (calcium and magnesium ions) and usually
     add sodium ions.  They are mostly ineffective against other contaminants of health
     concern.

G) Sediment Filters - Good for what they are designed for - removing particles from
     water - No other contaminant reduction takes place.  They are often used as a
     pre-filter for more expensive filtration systems to keep them from becoming
     clogged.
     Ceramic filters with a very small pore size (around 0.2 micron) are a special case
     of sediment filter and can be used in emergency situations to significantly reduce
     biological contaminants from water.  They are ineffective against chemical
     contaminants or viruses.

H) KDF Filters - A granular filter media which is promoted as changing free chlorine
     into non-irritating chloride, for reducing bacteria, and for precipitating some heavy
     metals like lead.  Works with hot water, and is often used in shower-head filters and
     in combination with activated carbon in household filtration systems.

 I)  Boiling - Effective for emergency disinfection of water only.  Pathogens are killed
     and volatile contaminants may be driven off, but many contaminants will remain.