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Re: Ion exchange water softener

>Date: Wed, 21 Jan 1998 00:28:17 -0800 (PST)
>From: cprokes at awinc_com (cp)
>Subject: Ion exchange water softener
>Could some one, please, explain to me why water softened by ion exchange
>water softener should not be used in fresh water aquarium. Even at 440ppm
>hardness, the process adds only about a tea spoon of salt per five gal of
>water, about the same amount recommended by some  to add anyway!?
>A clear explanation will be much appreciated.

With help by Roger Miller and others I posted last Sept. 25 a reference
table that estimates the amount of sodium that a watersoftners put into the
water after it exchanges either a Ca or Mg ions:

Estimated Sodium in softened water     ( 1ppm = 1mg/liter)
   |Before GH  |Converted Na |
   | (degrees) | (mg/liter)  |
   |-----------| ------------|
   |     1     |     8.2     |
   |     2     |     16      |
   |     5     |     41      |
   |     10    |     82      |
   |     15    |    123      |
   |     20    |    165      |
   |     25    |    206      |
   |     30    |    247      |
Another thing to remember, a watersoftner waste salt when it recharges the Zeolite.
Thus, one may expect to get even higher levels of sodium just after the recharge.

Since 440ppm hardness is about 25 degrees GH, this hardness would result in
at least 200 mg/liter sodium in the water. (Assuming the softner exchanges
almost all of the hardness.)

I usually screw up these following type of calculations, but here goes anyways:

I've seen estimates that 1 teaspoon NaCl weighs 3.5 grams, of which
2 grams (3.5 * 23/40 Na/(Na+Cl)) would be sodium.
So 1 teaspoon of salt into 5 gallons gives about 100ppm Na.
Thus 440ppm harness results in an equivalent of two teaspoons per five gallons.
(cprokes (Name?), I believe you forgot to take into account that two sodium ions
are needed to replace one Ca or Mg ion.)

Now comes the tuff part, the amount of sodium it takes to affect water plants
has somehow been set as 1 tablespoon (= 3 teaspoons) per 10 gallons as being
too much sodium. I'm sure the concentration varies depending on the type of plant.
I just know that from own experiences that Amazon Sword plants develop "burn
holes" in the leaves when using softned water from my 150ppm GH tapwater.

Also last September, an eighth-grade science student in Brooklyn, NY, 
Jacob Stulberg was going to study "The Effect of the Amount of Salt on the 
Growth of Aquatic Plants", so maybe we'll be hearing from him soon.

Ron Wozniak  Allentown PA, USA
AGA member
rjwozniak at lucent_com