Water Hardness Q?

DaveA76 · Jun 11, 2011

just been investigating the hardness of the water on our local water supplies test, which is the normal 1 that we use in the fish world, i know its degrees, but is it clark, french, or german ?

StandbySetting · Jun 11, 2011

Degree's is the hobby standard I believe.

Dodders · Jun 11, 2011

Everyone I know uses German, I think it's pretty universal.

DaveA76 · Jun 11, 2011

well ive been looking on here at the fish profiles

http

/www.aquariumlife.net/fishprof.asp

and seeing what is suitable to be in the water around here, the results from our local water authority for my post code says : -

Hardness as calcium (milligrammes per litre) 104

Hardness as calcium carbonate (milligrammes per litre) 260

Hardness as degrees Clark 18.096

Hardness as degrees French (°f) 26

Hardness as degrees German (°dH) 14.768

Hardness as mmol/l (millimoles of Ca) 2.6

so going by what you have said my water should be "Hardness as degrees German (°dH) 14.768" ? will be getting a tester soon but was just checking to see what was coming out of my tap or what is supposed to be

TwoTankAmin · Jun 11, 2011

Water hardness follows the following guidelines. The unit dH means ``degree hardness'', while ppm means ``parts per million'', which is roughly equivalent to mg/L in water. 1 unit dH equals 17.8 ppm CaCO[sub]3[/sub]. Most test kits give the hardness in units of CaCO[sub]3[/sub]; this means the hardness is equivalent to that much CaCO[sub]3[/sub] in water but does not mean it actually came from CaCO[sub]3[/sub].

Now I am going to confuse you even more. I measure my water using a TDS meter. TDS being Total Disolved Solids. And TDS are really not what is being measured what is being measured is the conductivity of the water. Confused? Maybe this will help, it is from http

/www.globalw.c...t/hardness.html

CAN YOU DETERMINE WATER HARDNESS FROM CONDUCTIVITY OR TOTAL DISSOLVED SOLIDS MEASUREMENTS?

General water hardness is related to the dissolved minerals in the water. General hardness is a misleading term that is often confused with carbonate hardness or temporary hardness, which is actually related to alkalinity and relates to the "buffering capacity" of the water (its ability to resist pH changes). This means that if the carbonate hardness is high then the pH will be extremely stable or alternatively if the carbonate hardness is low the pH of the water will be able to fluctuate easily. The term general hardness should be replaced with a simpler term: Hardness.
Water hardness is the measurement of the amount of ions which have lost two electrons (divalent cations) dissolved in the tested water and is therefore, related to total dissolved solids. The more divalent cations dissolved in the water the "harder" the water. Generally the most common divalent cations are calcium and magnesium, however other divalent cations may contribute including iron, strontium, aluminum, and manganese. Typically the other divalent cations contribute little to no appreciable additions to the water hardness measurement. A stream or river's hardness reflects the geology of the catchment's area and sometimes provides a measure of the influence of human activity in a watershed. For example, sites that have active or abandoned mines nearby often have higher concentrations of iron ions in the water resulting in a very high hardness degree.
Water hardness can be expressed in many different units including French degrees, German degrees, Clark degree, grains per gallon, mg/L CaCO3 (calcium carbonate), and ppm (parts per million). General conversions are below:

1 ppm = 1 mg/L CaCO3
1 ppm = 0.058 grains/US gallon
1 ppm = 0.07 Clark degrees
1 ppm = 0.10 French degrees
1 ppm = 0.056 German degrees
1 French degree = 1 hydrotimetric degree
1 Clark degree = 1 grain / Imperial gallon as calcium carbonate
1 French degree = 1 part / 100,000 calcium carbonate
1 German degree = 1 part / 100,000 calcium oxide
1 grain/US gallon = 17.1 ppm
1 grain/US gallon = 1.20 Clark degrees
1 grain/US gallon = 1.71 French degrees
1 grain/US gallon = 0.958 German degrees

Total dissolved solids (TDS) refers to a measure of all inorganic solids dissolved in the water. This means that it will measure ions that contribute to water hardness, tike calcium, but also those that do not, like sodium. The TDS measurement is a better reflection of the total mineral content of the water rather than a water hardness measurement. However, for estimation purposes, the water hardness can be roughly calculated by dividing the ppm (parts per million) measurement of the TDS by 10 giving a hardness value with an error of only 2-3 French degrees. TDS measurements can also be derived from relative conductivity measurement.

Conductivity is similar to TDS measurements. Conductivity is a measure of the ability of a substance to conduct electric current. Conductivity measurements offer a rapid and non-destructive way to measure ion content in the sample. The conductivity measurement is made with an electronic sensor or meter in micro/milli-Siemens per centimeter or ppm. Conductivity increases with increasing ion content, which means that in most cases it gives a good approximation of the TDS measurement using the conversion factor of 1 ppm = 2 uS/cm. Conductivity is temperature sensitive and is typically standardized to 25°C. While conductivity is a convenient way to get an approximation of the hardness of water it does have the drawback of combining all ions in the measurement, including those that do not contribute to the water's hardness. This hardness approximation gives an error similar to the TDS measurement of 2-3 French degrees of hardness.
Can you measure water hardness with a conductivity sensor or TDS sensor? Yes, however it depends on the accuracy that you want to have in your measurement.

I could not get the table showing approximate tds/conductivity/°f/hardness values- you will have to go to the link for the site to see that (sorry).

DaveA76 · Jun 11, 2011

so know youve baffled me which degree of measurement is used i cant fin answer anywhere in any uk sites ( i live in the uk)

TwoTankAmin · Jun 11, 2011

OK- it can be simplified if we rule out most of the terms that scientists need but fish keepers don't.

1. Water hardness is usually determined by measuring the total amount of calcium and magnesium present, since
the concentrations of these ions far exceed those of other alkaline earth metals. The accepted practice for
reporting hardness is as mg CaCO3/L, as if all of the hardness were from calcium carbonate. When in reference to liquids, 1 ppm = 1 mg/l.

2. The German dg scale is commonly used in aquarium test kits. The ones where each drop you add before it changes color is one degree. This translates into 17.8/17.9 ppm or mg/l equivalent of Calcium Carbonate.

3. In my first post it showed that 1 ppm = 0.056 German degrees. 17.8 x .056 = .9968 German dg and 17.9 x .056 = 1.0024 German dg.

5. Most of the test kits I know of for the hobby include a conversion chart so you can see how they work. I use the API GH/KH kit which uses 17.9 ppm/German dg.

6. Note that the drop method is not super accurate. For example: If you add 5 drops before the solution changes color that means your water has at least 89. 5 ppm but it could have as many as 107.3 ppm and still not reach the 6 dg minimum of 107.4 ppm. No kits is that perfect but you can get the idea.

Hope that makes it easier.