Re: R/O Units

[IDMiamiBob@aol.com]

Eric's explanation is correct.  Don's clain that the waste water is the 
hardness as the original tap water is not true.  Otherwise, you could just 
recylce the stuff back through the RO until 95 % or more of it was purified.  
In truth if you get 5 gallons of waste per gallon of RO water, then the waste 
is now 20% harder than before.  IN Z-man's case, where the original tap is 
175 ppm, and he gets 25 gallons of RO for 145 gallons of waste (1:5), the 
waste output is around 205-210 ppm, assuming the RO is as pure as with DI, 
which it isn't quite.  If you live in Southern CA, in one of those places 
where the water rolls out of the tap at 600ppm, then Don's waste is still 1/3 
as hard as yours.  You will get more waste for every gallon of RO, because 
the RO unit can only push the dissolved ions against the osmotic pressure in 
the tap water so far.  If you aren't using your waste water, then you are 
spending more per gallon for purified water than you may have calculated.  
Add in the cost of the waste water per gallon, and you may discover that a 
rechargeable De-ionizer is cheaper, or at least around the same price.

Bob Dixon


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