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U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION 10
1200 SIXTH AVENUE
SEATTLE. WASHINGTON 98101
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laMmJitau'iii
July 1989
££MSML
This fact sheet is intended to explain the most common types
of home water treatment units, what they are or are not capable
of doing, and why only some of them are registered with EPA.
Consumers, as well as sales people, should contact the local
water utility or health department, to obtain information about
the quality of water to be treated, before deciding whether a
home treatment unit or bottled water Is warranted. All public
water supplies are required to meet a number of primary drinking
water standards set by EPA and sometimes additional, or more
stringent, ones set by State governments.
Most home treatment units are the point-of-use (POU) type.
They treat water only at one tap. Units which treat all the
water that comes into the building are called point-of-entry
(POE). POE systems are generally larger and more costly.
Another way to classify home treatment units is by method of
installation. There are four basic classifications: 1] in-line -
sxanples would be POE units mounted near where the water supply
line comes into the building Dr under-the-counter POU units which
treat all the water going to a single tap; 2) line by-pass -
these are plumbed into the cold water tap under the counter with
the treated water going to a separate faucet; 3) counter top? and
4) faucet mounted. These classifications do not include self-
contained or portable units (i.e., pour-through types), which
comprise a small percent of the home water treatment market.
PURIFIERS Vfi. FILTERS
Two major categories of units are purifiers and filters. A
strict definition of "water purifier" might be thought of as
something that would reduce the treated water to pure H20. This
is not necessary or desirable for good human health, and it is
not easily achievable using home treatment.' A more functi6nal
definition would be one that refers to the microbiological safety
of water. EPA has set forth, in the "Guide Standard and Protocol
For Testing Microbiological Water Purifiers", a definition of
microbiological water purifier as a unit which "must remove, kill
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or inactivate all types' of disease-causing microorganisms from
tho water, including bacteria, viruses, and protozoan cysts, so
as to render the processed water safe for drinking, to qualify,
a microbiological purifier must treat or remove all types of
challenge organisms to meet specific standards" (e.g". , 99.9999%
reduction in bacteria, 99.99% reduction in viruses, and 99.9%
reduction in cysts). Purification technology may use physical
and/or chemical means. Home water filters are not recognized as
being able to remove all disease-causing microbes from water and
should not be used on "raw" water, but rather, only on water that
has been disinfected (e.g., by a municipal water facility).
Disinfection seldom kills all bacteria in water, so there is
usually a harmlessly low level of bacteria in drinking water. A
water filter may collect not only particles or certain chemicals,
but also bactaria. Bacteria which collect on the filter can
multiply and actually cause more bacteria to come out than went
in- Some manufacturers of carbon filters add a chemical, such as
silver, to the carbon to control bacterial growth. These filters
often will claim to be "bacteriostatic". The silver does hot
kill bacteria but is intended to inhibit their multiplication,
studies disagree whether or not the bacteriostatic effect is
significant. Fortunately, the types of bacteria most commonly
found on water filters in homes receiving municipally disinfected
water have not been shown to pose any threat to health.
If you are planning to treat raw, untreated water (partic-
ularly surface water) for your private drinking water supply,
contact the local or state health, department and ask them to
reviev your disinfection/treatment plans. If you are planning on
supplying 15 or more connections (i.e., homes) or more than 24
people from a water supply, there are specific requirements that
must be mets again, call your state health department or
whatever agency which has jurisdiction for public water supplies
in your state.
RF.fiTSTERF.D vs. NON-REGISTERED
In EPA registration of water treatment units the key words
are "chemical" and "claim". If a water treatment unit contains a
chemically active ingredient that inhibits or reduces the growth
of microorganisms, then the unit and the establishment which
produces the unit must be registered according to the Federal,
Insecticide, Fungicide, and Rodenticide Act (abbreviated FIFRA).
Such units must have an EPA establishment number (EPA Est. no. )
and may also have a registration number (Reg. no.) on the label.
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[jKOTSTERED VS. NOH-REGISTERED {cOnt.)
if the manufacturer makes a claim about inhibiting' or ro&uc-1
ing bacteria or other peats in water, but uses no chemical in the
device, then only establishment registration is required. If a
unit contains no such chemical and no pesticidal claims are made,
neithor the unit nor the manufacturer must be registered'.
Registration is not an approval by EPA nor a test of a
unit's effectiveness compared to manufacturer»s claims. A
registration number merely indicates the presence of a pest-
controlling chemical, which should not itself contaminate the
water passing through the unit. An establishment number indi-
cates the EPA has been informed by a company that they are
producing treatment units which claim to inhibit or reduce
bacteria or microorganisms in water.
Remember." the key wordst "chemical" and "claim". If you see
both a "Reg." and an "Est." number, then a chemical is present
anti a pest-controlling claim is being made. If you only see an
"Est." number; then claims are being made but no chemical is
used. Claims or chemicals without an EPA Est. or Reg. number on
the unit mean the requirements of FIFRA are not being followed.
COMMON TECHNOLOGTES AMD THEIR FUNCTION
Water softeners The most common type of water softeners
chemically exchange positively charged
molecules or ions (like iron, manganese,
selenium, silver, cadmium, calcium,
chromium, copper) by replacing them with
sodium. Regular coarse salt (sodium
chloride, NaCl) is normally used, but
potassium salts are also available.
This process can eliminate the nuisance
of stained clothes and fixtures, save on
soap and detergent, reduce film left on
skin and dishes, and deter scale build
up in pipes. However, it does add salt
to the water, may make the water more
corrosive, and requires regular
maintenance.
Physical Filters Those can be made of fabric, fiber,
ceramic, screening, diatomaceous earth
or other material. Some can remove
microorganisms (cysts, larger bacteria)
and very small particles (asbestos
fibers): but most only remove larger
particles; like grit, dirt or rust.
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COMMON TECHNOLOGIES AND THEIR FUNCTTON (cont.)
Activated Carbon Available in several forms: granular
Filters activated carbon (GAC); powdered acti-
vated carbon (PAC); PAC coated paper
filters; and pressed carbon block fil-
ters. Activated carbon can "remove many
organic chemical contaminants (given
enough contact time) and thus removes
most tastes, odors, and colors from
water. Organics which are less soluble
in water are removed more easily than
soluble ones. Some inorganics can be
removed (like chlorine), but activated
carbon is not an effective technology
for removing most inorganics ('like salts
and metals, including lead) nor does it
effectively remove microorganisms. *Thus,
carbon filters by themselves are not
recommended for use on water which is
microbiologicaliy unsafe. Carbon filters
do eventually get overloaded with con-
taminants, allowing any additional ones
to pass through (following maintenance
recommendations should prevent such
overloads). Also, bacteria can collect
and multiply on a filter's surface.
Periods of non-use, especially in warm
areas, promote bacterial growth and can
lead to undesirable tastes or odors of
filtered water. There is no evidence to
confirm that this threatens health.
Reverse Osmosis (RO) A complete RO system consists of an RO
module, a storage tank, and a separate
faucet. The module, the heart of the
system, contains a semi-permeable
membrane which allows water and some
organic chemicals to pass through and
collect in the storage tank. Other
chemicals and particles are rejected and
then washed off the membrane into a
waste stream. About 75% of the water
introduced is wasted. Thus, 4 gallons
of water in produce about 1 gallon of RO
filtered water. Treated water comes out
much slower than water from a regular
tap, so a tank is used to store the
treated water; that way, it is available
when you want it. RO is effective at
removing most all inorganics; ' salts,
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COMMON TECHNOLOGIES AND THEIR FtJNC.TTON (cont. )
RO Both dis-
solved and suspended solids (also
referred to as turbidity) adversely af-
fect the performance of UV disinfection,
so does dirt build-up on the transparent
parts of the unit. Periodic checking
and maintenance is necessary.
Distillers Distillers come in many different shapes
and sizes, but what they all have in
common is that they all vaporize water
then condense it. During this process
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C511M0MJ^;CHN_0r.OGT^S^MLDjatt:!R_P_UNCIIQN (cont. )
nistillers
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APPENDIX A.
REFERENCES ON DRINKING WATER Afjp HOME WATER TREATMF.MT
I. "Can I Drink; the Water?", League of Women Voter's of Calif.,
Sacramento, CA, 1987. (A brief fact sheet that tells
consumers how to find out about their drinking water.)
Z. "Drinking Water", Concern, Inc., Washington, D.C., Dec 1986,
3ipp. (A good introduction to the complex issues of drinking
water management and protection with guidelines for public
participation,)
3. "Home filters to 'purify' water". Changing Times. Feb 1981,
pp44-47. (31 units reported on.)
4. "Water filters". Consumer Reports. Feb 1983, pp68-73+.
{17 filters tested.)
5. "Studies on Home Water Treatment Systems". Journal awwa.
April 198 4, ppl26—130. (A summary of EPA info from '79-'81.)
6. "Point-of-Use Treatment to control Organic and inorganic con-
taminants In Drinking Water". EPA Research & Development
Project Summary. EPA/GOO/S2-85/112, Jan 1986, (Announces
findings of 3 separate research projects.)
7. "Bacterial colonization of Point-of-Use Water Treatment
Devices". Journal awwa. Feb 1985, pp72-80, (A technical
article. One simple conclusion drawn was that they would
not recommend carbon filters for use on microbiologically
unsafe water supplies.)
8. "Efficiency of point-of-use treatment devices". Journal awwa.
Jan 1983, pp42-50. {Examines two systems - one GAC and one
RO/GAC, for their ability to remove organic, inorganic,
microbiologic, and particulate contamination.)
9. "On Tap: Safer, Better-tasting water", consumer Digest.
Jan/Feb 1984, pp40-41 + 57. (Some good background info,
non-technical and generally correct. Ranks 8 units using
EPA test results.)
10. "Giving your water the treatment". New Shelter. May/June
1985, pp20-23.
II. Water Treatment Handbook: A Homeowner's Guide. Rodale Press
Product Testing Department. Rodale Press. Emmaus, PA. 1985.
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IZ. "Troubled Water". Rodale's Practical Homeowner. January
1987, pp?.7-29 I 34-39.
13. "How to tap into the right system for the job". San Josr
Mercury News. May 30, 1987, pplC-2C. (A general guide to
several home treatment methods and test results on 22 units
- source: Rodale Press Product Testing Department)
14. "DrinJcing Water Treatment Units: Aesthetic Effects (Standard
No. 42)", National Sanitation Foundation, Ann Arbor, MX,
Revised June 1982.
15. "Drinking Water Treatment Units! Health Effects (Standard No.
53)", National Sanitation Foundation, Ann Arbor, MI, Revised
June 1982.
16. "Reverse Osmosis Drinking Water Treatment systems (Standard
No. 58)", National Sanitation Foundation, Ann Arbor, Ml,
November 1986.
17. "Cation Exchange Water softeners (Standard No. 44)National
sanitation Foundation, Ann Arbor, MI, December 1987.
Note: The National Sanitation Foundation (NSF) is a nonofficial,
not-for-profit research, education and service organization which
develops standards and criteria for equipment, products and serv-
ices that bear upon public health and the environment. NSF also
tests products, systems and services against established standards
and publishes listings annually of those in full compliance with
the standards or criteria.
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