Softening water by boiling it.

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beervoid

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I was told one could pre-boil the water to make it softer.
Is there anyone here who can tell how much ppm of which minerals will go down this way?
I"m especially interested in getting the sodium which is 100ppm in the water lower.
If anyone has suggestions besides diluting with soft water (ro or distilled)
Thank you.
 

ajf1994

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I would think boiling would increase the hardness. Water is evaporating, leaving minerals behind. The minerals won’t evaporate, you’d just be condensing them.
 

jtratcliff

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Certain minerals will precipitate... Calcium Carbonate, for instance... If you notice a chalky white build-up on your tea kettle, this is stuff being removed from the water via boiling...

I can't answer the OP's specific question about sodium, perhaps @ajdelange or some other knowledgeable HBTer can chime in...
 
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beervoid

beervoid

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Certain minerals will precipitate... Calcium Carbonate, for instance... If you notice a chalky white build-up on your tea kettle, this is stuff being removed from the water via boiling...

I can't answer the OP's specific question about sodium, perhaps @ajdelange or some other knowledgeable HBTer can chime in...
After a bit of reaearch I found the answer in the brunwater documentation.
You are right Calcium and Carbonate will drop the rest stays.
 

jtratcliff

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100ppm sodium isn't horrible... I think Palmer recommends 50-150... about all you can do is dilute w/ RO or distilled.
I'm not a water chemistry guy, but I don't know of any easy additive to remove sodium...
,
 

Silver_Is_Money

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PPM Ca post boil = ppm Ca pre boil-((ppm alkalinity pre boil*61/50 - ppm alkalinity post boil*61/50)/3.05)

Where (in the real world):
The ppm of alkalinity post boil can typically be driven no lower than roughly about 65 ppm, and this requires that the ppm of calcium remaining post boil be driven down to no lower than roughly about 12 ppm.

The bottom line is that (in the real world) if calcium goes below ~12 ppm before alkalinity falls to ~65 ppm, then at this juncture you must add more calcium (such as gypsum or calcium chloride) to the water to raise the calcium to above 12 ppm and continue boiling. And another bottom line is that (in the real world) alkalinity can not typically be boiled out to below roughly 65 ppm. Which means that bicarbonate can not be boiled out to below roughly 79.3 ppm. These are the real world limits for alkalinity removal. The driving force behind alkalinity removal via boiling is the presence of sufficient calcium.

And OTOH, if all you want to do is get rid of most of the hardness by getting rid of the calcium, the driver for this case is the presence of sufficient alkalinity. If after boiling the remaining alkalinity is present at quantities sufficiently above 65 ppm you might even be able to drive calcium to near zero.

This method will not remove very much magnesium.

All credit here must go to Martin Brungard and A.J. deLange, and I hope I got the 'real world' essence of this correct, or that they will pop in and set me straight if I got it wrong.
 
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ajdelange

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The reaction involved is Ca++ +2HCO3- ---> CaCO3 + CO2 + H2O. A similar reaction takes place with Mg++ and bicarbonate but the magnesium salt is more soluble than the calcium one and thus not so much magnesium is removed.

Now as to what practically happens when you heat water: one mEq of calcium (20 mg) reacts with 1 mEq of alkalinity (50 ppm as CaCO3) to drop 1 mmol of chalk. Precipitation reactions are a bit hard to predict so we use the rule of thumb that the lesser of the alkalinity or calcium hardness will be reduced to 1 mEq/L. Thus if Ca hardness is 3 mEq/L and alkalinity 2 then alkalinity will be decreased to about 1 reducing the Ca to 2 thus removing 1 mEq/L alkalinity. Conversely if alkalinity 3 mEq/L and hardness 2 then hardness will be reduces by 1 to 1 taking out 1 of alkalinity with the calcium. Thus to effectively decarbonate water the calcium hardness must be greater than the alkalinity. Thus soft alkaline water cannot be decarbonated by this method unless hardness is first supplemented by adding calcium salts.

Sodium cannot be removed by this method. The only way to remove sodium is by RO filtration or distillation or the equivalent obtained when high sodium water is diluted with RO or DI water (both of which are soft but that does not matter - what matters is that they are low in sodium). As OP's concern is sodium reduction boiling nor lime treatment are options for him.
 
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