Aim: To calculate grams NaCL or NaHCO3 added to 1 gallon (3.785 L) 
distilled water to create water with "hardness" of  approx. 3 to 4
grains for use below.

Background: 
Purchased an expensive Rowenta Steam Generator Iron and want to
minimize scale buildup within boiler unit.
I don't know if the boiler is stainless steel or some other material. 
The manual recommends water with hardness to 12 grains and sternly
advises against distilled water.
If water is harder than 12 grains, manual recommends diluting to 50%
with distilled water.
I'm assuming the water needs some dissolved ions to function properly,
but I want to keep this to a minimum to avoid scale buildup.

Answer(s) desired:
1. Grams NaCL or NaHCO3 added to 1 gallon (3.785 L) distilled water to
create water with "hardness" of  approx. 3 to 4 grains.
2. Which is better choice for purpose: NaCL or NaHCO3?

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Request for Question Clarification by smudgy-ga on 26 Jun 2004 20:51 PDT

Hi herostratus,

According to several sources that I have found, general water hardness
represents the amount of Mg++ or Ca++ ions in water. In order to
affect the water hardness, you'll need to dissolve something that has
magnesium or calcium in it (for example, calcite, CaCO_3, or calcium
bicarbonate or magnesium bicarbonate). You won't be able to affect the
hardness by adding NaCl or NaHCO_3.

There -is- a separate measurement called Carbonate hardness, which is
a measurement of how much CO_3 is in the water. If your generator
manual referred simply to "water hardness" it is most likely -not-
talking about this measurement.

I can calculate how much magnesium or calcium bicarbonate you need to
add to change the water hardness to the desired 4 grains, if you would
like.

Thanks,
smudgy.

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Clarification of Question by herostratus-ga on 27 Jun 2004 04:26 PDT

Consider the aim:

What I need clarification on is "hardness" as it refers to the
boiler/steam generator; whether by electrolysis (?) or heat.

I wish to minimize scale buildup in the tank and assembly by making
the solution myself from distilled H2O and a salt. I'd also like to
keep corrosion to a minimum.

I can calculate the grains to grams ratio as well, although as you
noted the terms are just a wee bit hazy... What I don't understand is
the big picture.