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Re: Reverse Osmosis Units


There are lots of different points to consider before purchase, I'll try
and give a few hints.

Firstly: the capacity is dependant on water temperature, pressure and
amount of dissolved solids in the water (conductivity). Higher pressure,
higher temperature and purer tap water increases RO-output.

RO-units waste water. To produce 1 gal of purified water it may take up
to 6 gals of tap water, depending on quality and age of the unit. There
are units that recirculate the waste-water and thus wastes less water.
If you pay for your water you may want one of those "waste less"-units,
though they cost more.

There are two different types of membranes on the market, one that is
sensitive to chlorine (TFC's) and one insensitive (CA). The upside of
TFC-membranes are longer life and higher output. Downside is chlorine-
sensitivity and a higher price.

__What you need?
For TFC-equipped units you'll need a prefilter and a carbon filter, for
CA-units you'll only need the prefilter.

As for maintenance you should make sure that the prefilters are easy to
change. You also want to flush the unit to clean the membranes every
other day or it will clog.

__My unit?
I can only add some info on the unit I bought. It's an Aqua Medic (made
in Germany) with a TFC-membrane. Several others around here have one as
well and they're quite good. The output water is between 0 and 10
microSiemens/cm from a tapwater of 190-220, so it removes at least 95%.

__More info?
Check out http://www.aqualink-too.com/columns/k-love.html
(lots of info on reverse osmosis)
or http://www.ee.pdx.edu/~davidr/discus/ROsurvey.html
(survey on brands and customer-satisfaction)

Hope any of this helps

- -- 
Fredrik Ljungberg, Linkoping, Sweden