Steve

The carbon filter is necessary in most water purification systems if the
input water has greater than 1 ppm of chlorine.  Without the carbon filter
the life of the bed is materially shortened.  Depending on several factors,
it could shorten the bed life by about 50%.  In the western US where we see
300 to 1000 ppm TDS we normally use a RO ahead of the DI bottles and here it
is mandatory to use a carbon filter in front of the RO membrane if your water
chlorine concentration is greater than about 0.8 ppm of chlorine.  It is
especially critical if some of the organic-chlorine substitutes that are
popular with some water companies are used.  Chlorine can run as high as 4
ppm in some supplies.

All water is not furnished to the user in equal form  and if you are using
the DI water to replenish a plating bath, it is mandatory that you use a
carbon filter, if your water is from a surface source (river or lake water).
Some of these materials that can be removed from water with a carbon filter
will really screw up a plating bath.  If you are using the water for washing
the flux from circuit board assemblies, most organics arriving in the water
do not interfere with the cleanliness.

Your water supplier can furnish you a complete listing of the materials in
your water, and looking at these you can make choices as to whether to use
carbon or not for your operation.

Phil Hinton      .

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