Lime/Calcium Deposits

[BallAquatics]

That's fascinating stuff.  I'll have to test some water from the softener to see if mine is 0 GH as well.  In all these years, I've never once tested water from the softener.....

Dennis

[PaulineMi]

I'm not a fraction of the man Bill is when it comes to smart stuff but I know this...Everywhere I have lived in my fish keeping career my gH has been 0.  If there is gH at all it must be a trace amount.  It has never bothered my fish.  Remember, these fish come originally from the Amazon where the water is devoid of minerals.

Just out of curiosity, if the water from the softener is 300 TDS, what is you're kH?

The KH from the well and softened tap both test out at 16.  The TDS from the well is 311, from the softened tap it's 347.

[BillT]

OK. Here is how I would think about this water chemistry stuff, hope its not too geeky:

Water is H₂O as everyone knows, but it is also found in several other forms:
OH^-(hydroxyl ion)
H⁺
H₃O⁺ (I forget the name of this one but its is thought to be the most common form of a free roaming H⁺ (hydrogen ion) since this would be a more stable form.

Any pure or unpure water will be a mix of these forms. All the numbers of charges on all the molecules in a container will have to be equal to zero (0) or the water in the container will have a charge (not normal). Since charges are neither created nor destroyed, whenever a negative ion forms, a positive counter ion (or maybe two partial charges) would have to also form. An example is:
H₂O <--> H⁺ + OH^-.
All these molecules are always changing between these different forms all the time. Many things change back and forth alot.

You can think of atoms as little balls. Plus charged center with electrons around it with equalizing negative charges. Atoms with different numbers of center charges are different elements, the most basic chemicals.
Molecules are combinations of atom balls. If a little ball with a charge (hydrogen) leaves, it can do so with one less electron making it +1 and the rest of the molecule it left -1. Certain kinds of atoms will stick to others strongly, in particular ways, and in particular proportions. This makes specific chemicals that have specific geometrical arrangements of different atoms. 

The numbers involved in these processes are huge. A liter of water contains 6.03 x 10²³ molecules of H₂O. That number is 10 plus 22 more zeros, times 6.03, or: 60,300,000,000,000,000,000,000.00. You can therefore have present some of very small proportions of chemical forms, because there are so many molecules and they are always changing.
Changing the balance of all these forms of water is changing the pH.

There are a standard set of ions and other chemicals dissolved in water.
The major ones are:
Na⁺(sodium ion)
K⁺(potassium ion)
Cl^- (chloride {the chlorine ion})
Mg⁺⁺(magnesium ion)
Ca⁺⁺(calcium ion)
There are lots of minor ones.

Inorganic Buffers (ions or ionizable {meaning can become charged}, stabilizes certain pH's)
CO₃^-- (carbonate ion)
PO₄^---(phosphate ion)
SO₄^--(sulfate ion)
These have multiple charges and can be partially ionized, such as being only -1 because they have bound a positive ion like H⁺, which is always available due water ions being all over the place.

A dried chemical added to the water will be unionized. It will be a molecule (or crystal) of equal numbers of plus and minus charges neutralized in the structure of the molecule. Water is such a good solvent because is it slightly ionized. By its very nature, it is a mix of all the forms described above. This slightly ionized environment is usually great for dissolving solids of an ionizable chemical. Doing this puts equal number of plus and minus charges into the water.

This could also involve releasing H⁺ from things like sodium bicarbonate, various phosphate buffers, or other things.

Organic buffers would have carbon in them, probably have something to do with something alive and would be a complex mess of different things chemically speaking (filter them out with carbon, or RO).

All of these ionizable things can be found at some (big to very very small) concentration in the water. Different combinations will be favored, be more stable forms (at the particular pH), and be represented as a larger percentage of the whole population of molecules dissolved in the water.

KH is carbonate (with a K because its German I guess) hardness, which should be a measure of amount of carbonate (CO₃^--). I like ppm (parts per million, the same as mg/L (milligrams per liter)) since it relates directly to a measured amount), but they are both a chemical measure of the amount of carbonate in the water. Carbonate is probably the most common kind of buffering people think about. Phosphate is a great buffer for biology labs, but is too good a food for algae as well as bacteria and fungi for a lot of uses. Sulfates are used in salt mixes.

GH measures the amount of Ca⁺⁺ and Mg⁺⁺ in the water.
So between KH and GH you are only measuring two ions and one buffer.
You can therefore put water into your watersoftener and have water with 0 GH (Ca⁺⁺ and Mg⁺⁺), 0 KH (CO₃^--) come out, but have a lot of conductivity (current through the water carried between the two electrodes by ions moving in the water).

The conductivity in the water coming out of a water softener is due to the ions that water softeners release when they take up the other ions. Without a chemical test you can't really tell what ion is carrying the charge, unless you already know something about your water. An extreme example would be if you are measuring a known salt mix, you can make a look-up table to go from conductivity to how much of various chemical components based upon measurements you made when making up the various dilutions and concentrations of that salt mix to get measurements to make up the table.

My understanding of water softeners is they are a solid matrix of some chemical with bunch of surface area (where the reactions with things dissolved in the water occur). These surfaces probably have a charge on a molecule found all over the place on these surfaces. Depending on the charge, the chemistry of the charged molecule, maybe the geometry of the surface site, the charged sites on the surface will be able to bind a charged ion, removing it from the water and therefore out of solution. To do this, the solid matrix will have to release an equal amount of charge back into the water. Could be sodium, could chloride, could be a hydrogen ion (H⁺). Or it could absorb a positive and a negative ion at the same time (no charge change).

For example, sodium (Na⁺) levels are low and some other ion is high (in a water softener filter), two sodiums (Na⁺) can be released (and removed by flow) if their charged sites are close to each other, the pair of sites could be taken by a single calcium (Ca⁺⁺) or magnesium (Mg⁺⁺) ion. Getting a chemical to make your filter matrix out of would be benefit from having a chemical with two ionizable sites located in such a way that they could bind calcium/magnesium weakly (so it could be removed for reuse).

High sodium or maybe potassium levels are used to recharge a water softener. In this case the high levels of sodium (Na⁺) ions will displace the absorbed calcium ion from the matrix so the filter matrix can be removed from the now dissolved calcium (Ca⁺⁺) (change out a soaking solution in a larger unit maybe) and reused to get some more.

[BallAquatics]

WOW!  I thought I understood hard water, but found that I no nothing.  LOL

Very enlightening Bill, thanks for the great explanation.  I always wondered why in Europe and Asia they tested using conductivity and made it difficult to compare the two results, but with a single line in the explanation, the light went off in my head.....

So between KH and GH you are only measuring two ions and one buffer.

Dennis

[PaulineMi]

WOW!  I thought I understood hard water, but found that I no nothing.  LOL

Very enlightening Bill, thanks for the great explanation.  I always wondered why in Europe and Asia they tested using conductivity and made it difficult to compare the two results, but with a single line in the explanation, the light went off in my head.....

So between KH and GH you are only measuring two ions and one buffer.

Dennis

And would that buffer still be the KH? That which we count on for pH stabilization in the aquarium.

[BillT]

And would that buffer still be the KH? That which we count on for pH stabilization in the aquarium.

The KH buffer is carbonate. If KH = 0, then there should be no carbonate present if the test was specific to carbonate (but does not measure other buffers) rather than just measuring alkalinity (which measures the amount of change in pH when an acid or base is added).

There are plenty of other possible buffers. The most common ones are phosphate and sulfate, but lots of other could also be in there.
Not all would be useful. Buffers work best in different pH ranges (like pH 10-11 or 3-4 and some are poisonous (like some related to arsenic). Some are too weak to be very effective.