Culligan Drinking Water System - Manual (Page 20)

Arsenic Fact Sheet Arsenic (abbreviated As) is found naturally in some well water. Arsenic in water has no color, taste or
odor. It must be measured by a lab test. Public water utilities must have their water tested for
arsenic. You can get the results from your water utility. If you have your own well, you can have the
water tested. The local health department or the state environmental health agency can provide a
list of certified labs. The cost is typically $15 - $30. Information about arsenic in water can be found
on the internet at the US Environmental Protection Agency website:
www.epa.gov/safewater/arsenic.html.
There are two forms of arsenic: pentavalent arsenic (also called As (V), As (+5), and arsenate) and
trivalent arsenic (also called As (III), As (+3), and arsenite). In well water, arsenic may be pentava-
lent, trivalent, or a combination of both. Special sampling procedures are needed for a lab to deter-
mine what type and how much of each type of arsenic is in the water. Check with the labs in your
area to see if they can provide this type of service.
Reverse osmosis (RO) water treatment systems do not remove trivalent arsenic from water very
well. RO systems are very effective at removing pentavalent arsenic. A free chlorine residual will rap-
idly convert trivalent arsenic to pentavalent arsenic. Other water treatment chemicals such as ozone
and potassium permanganate will also change trivalent arsenic to pentavalent arsenic. A combined
chlorine residual (also called chloramine) may not convert all the trivalent arsenic. If you get water
from a public water utility, contact the utility to find out if free chlorine or combined chlorine is used
in the water system.
The Culligan Water Tower CWT35ST3.0 is designed to remove pentavalent arsenic. It will not con-
vert trivalent arsenic to pentavalent arsenic. The system was tested in a lab. Under those conditions,
the system reduced 0.30 mg/L (ppm) pentavalent arsenic to 0.010 mg/L (ppm) (the USEPA standard
for drinking water) or less. The performance of the system may be different at your installation.
Have the treated water tested for arsenic to check if the system is working properly.
The RO component of the Culligan Water Tower CWT35ST3.0 must be replaced every 3-5 years to
ensure the system will continue to remove pentavalent arsenic. The component identification and
locations where you can purchase the component are listed in the installation/operation manual.
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