KH <= GH

Edward Shave

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A short time ago A thread I started in another place was closed down by a moderator because I was arguing that KH can never be greater than GH. In fact the moderator went so far as to say this was nonsense.

Now this really threw me because I'm sure I'm right....

Since I'm posting this in the "Water Chemistry" section I'm hoping some knowledgeable person will confirm this and thus save my sanity lol.
 

ian_m

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Can't see any deleted/closed post by you. All posts & threads by you are still open and active (or not).o_O
 

Nuno Gomes

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A short time ago A thread I started in another place was closed down by a moderator because I was arguing that KH can never be greater than GH. In fact the moderator went so far as to say this was nonsense.

Now this really threw me because I'm sure I'm right....

Since I'm posting this in the "Water Chemistry" section I'm hoping some knowledgeable person will confirm this and thus save my sanity lol.
If you are sure, why do you need someone to confirm you're right?

And you're wrong by the way, but I do understand the mixup, the General in GH makes people think GH includes KH.....
 

Edward Shave

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Daveslaney

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GH is Total Hardness. Total hardness = Carbonate hardness (KH) + non Carbonate hardness.
Sorry to say but I think you just answered your own question here.
GH= KH PLUS NON CARBONATE HARDNESS. So there for the KH can never be greater than the GH.
But according to the link provided by Andrew GH is actually just the magnesium and calcium.
So the KH can be higher than the GH.
 
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X3NiTH

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Semantics!

Total Hardness = Permanent Hardness + Temporary Hardness

Permanent Hardness = Chlorides + Sulfates etc.

Temporary Hardness = Carbonates

Total = All Ions (not just Ca and Mg)
Permanent = Not removed by boiling
Temporary = Removed by boiling
 

Edward Shave

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Semantics!

Total Hardness = Permanent Hardness + Temporary Hardness

Permanent Hardness = Chlorides + Sulfates etc.

Temporary Hardness = Carbonates

Total = All Ions (not just Ca and Mg)
Permanent = Not removed by boiling
Temporary = Removed by boiling
The "Temporary Hardness" you refer to in your first equation is another name for Carbonate Hardness or KH. So by your definition KH must be less than Total Hardness (GH).

Strictly speaking Total Hardness is the sum of multivalent cations so for example monovalent ions such as Na+ (sodium) are not included.
 

Edward Shave

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Sorry to say but I think you just answered your own question here.
GH= KH PLUS NON CARBONATE HARDNESS. So there for the KH can never be greater than the GH.
But according to the link provided by Andrew GH is actually just the magnesium and calcium.
So the KH can be higher than the GH.
GH or total hardness is a measure of the multivalent cations present in the water. Principally Ca++ and Mg++

KH or carbonate hardness is that portion of GH cations associated with carbonate/bicarbonate anions. Despite the name it is the multivalent cations and not the carbonate anions that contribute the hardness property.

NKH or non carbonate hardness is the remainder of the multivalent cations not associated with carbonates.

Thus GH=KH+NKH leading to the conclusion that KH<=GH
 

dw1305

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Hi all,
GH or total hardness is a measure of the multivalent cations present in the water. Principally Ca++ and Mg++ KH or carbonate hardness is that portion of GH cations associated with carbonate/bicarbonate anions. Despite the name it is the multivalent cations and not the carbonate anions that contribute the hardness property.
This is all in the the OP's (@Edward Shave), other thread, <"Boiling off KH">.
Total Hardness = Permanent Hardness + Temporary Hardness

Permanent Hardness = Chlorides + Sulfates etc.

Temporary Hardness = Carbonates

Total = All Ions (not just Ca and Mg)
Permanent = Not removed by boiling
Temporary = Removed by boiling
That one. When you add a monovalent carbonate (like sodium bicarbonate (NaHCO3)) you have raised the carbonate hardness (dKH), electrical conductivity (you've added Na+ and HCO3- ions), pH and the alkalinity, but you haven't raised the dGH, because you haven't added a multivalent cation.

The best summary of water hardness I've found are still the ones on "the Krib" <"Water Hardness"> and <"Hardness (incl. History">, mainly because they include the history and definition of the units.

A definition of "Total Hardness" is here: <"Total Hardness">

cheers Darrel
 

zozo

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Latest Water company report.. :)
Knipsel.JPG


My test kit averagely results in 11 - 12 dKh slight color switch starts at 10.

1 dKh = 17,86mg/l HCO3 190,38/17.86 = 10,66

This is an average report it fluctuates between 190 and 210 mg/l HCO3 (but did cut that out off the report to make the image smaller), test kit is pretty accuratly coresponding the WC report.

My Gh test results is 6°dH, 1 mmol/l = 5,62 ºdH.. Coresponds with above 1,09 mmol/l

1°dH = 10mg/l CaO or 10mg/l MgO
Dunno how that corresponds with the above 32,29 mg/l Ca and 7,53 mg/l Mg i'm missing an O there and the knowledge.

But what we can read from the test kits it seems my kH has a higher number than my gH.. :)
 

Edward Shave

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...When you add a monovalent carbonate (like sodium bicarbonate (NaHCO3)) you have raised the carbonate hardness (dKH)...
You are right, sodium bicarbonate will raise the value of KH but not beyond GH. What your really doing is raising the alkalinity and the two values are the same so long as KH < GH. Alkalinity on the other hand can be greater than GH.
 

zozo

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Your test kit is measuring Alkalinity (A) not KH. A = KH so long as KH<GH. If A>GH then KH=GH.
I know that both tets are determined by adding acids and the amount of drops reflects in a pH change again in a color change. :)

I didn't reply to discuss the issue i don't posses the knowledge i can't argue nor agree, just thought to give an example from my personal situation, that my tap water measeres kH 10 value, a higher number than the gH 6 value. Considered hard in carbonates and soft in CA and Mg.

But obviously i'm far from understanding yuor question and point.. Sorry..
 
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