AQUAX® Total Water Hardness Test Kit

What is Water Hardness?

Water is a good solvent and picks up impurities easily.  Pure water is tasteless, colorless, and odorless as often called the universal solvent. As water moves through soil and rock, it dissolves very small amounts of minerals and holds them in solution. Calcium and magnesium dissolved in water are the two most common minerals that make water “hard”. The degree of hardness becomes greater as the calcium and magnesium content increases and is related to the concentration of multivalent cations dissolved in the water.

Why Water Hardness is important?

Many industrial and domestic water users are concerned about the hardness of their water. You may have felt the effects of hard water, literally, the last time you washed your hands. Depending on the hardness of your water, after using soap to wash you may have felt like there was a film of residue left on your hands. In hard water, soap reacts with the calcium (which is relatively high in hard water) to form “soap scum”. When using hard water, more soap or detergent is needed to get things clean, be it your hands, hair, or your laundry.

You can also notice some spots or film on glass dishes after unload them out of in the dishwasher. This is harder water residue, not dangerous, but unsightly. When hard water is heated, such as in a home water heater, solid deposits of calcium carbonate can form. This scale can reduce the life of equipment, raise the costs of heating the water, lower the efficiency of electric water heaters, and clog pipes. Hard water can even shorten the life of fabrics and clothes.

As this picture of an inside of a water supply pipe shows, long-term movement of hard water through a pipe can result in what is called scale buildup. Just as in the human body where blood vessels can be reduced in inside diameter due to cholesterol buildup, water pipes can gradually close up resulting in less water movement through the pipe and a lowering of water pressure.

That is why, the water quality and water hardness is very important both in the industry and in daily life! It is important parameter and has to be monitored constantly.

Measures of water hardness

General guidelines for classification of waters are:

German Hardness d ºH French Hardness f ºH CaCO3 (mg/L or ppm) Calcium Carbonate Evaluation
0 – 4 0 – 7 0 – 71 Very Soft
4 – 12 7 – 21 71 – 160 Medium Hard
12 – 17 21 – 30 160 – 213 Hard
> 17 more than 30 more than 213 Very Hard

NOTE: Other organizations may use different classifications.

Measuring the Total Water Hardness with AQUAX® Test Kit

The hardness of water can be approximated with AQUAX® Total Water Hardness Testing Kit.

The AQUAX® has been designed in One-Reagent (Hardness Indicator Buffer Solution) for easy, quick and correct determination of water quality by Titrimetric Method. The easy drop-and-see application provides reliable results within few seconds.


  1. Fill the test container with the water to analyzed, shake for two or three times and pour off. Fill 5 mL water sample to be analyzed.
  2. Add 1 drop from hardness indicator Buffer Solution and shake the test container.
    • a) If the water sample color turns into green-bluish, no hardness is present. In this case, finalize the experiment and report it as Zero Hardness.
      b) If the water sample contains any hardness, the color will turn into pink-reddish.
  3. If the color turns pink – reddish continue adding hardness indicator Buffer Solution drop by drop shaking after each drop and observing the color.
  4. When the color turns into green-bluish finalizes the experiment.

RESULT: The number of drops spent during the experiment is recorded as amount of hardness in German unit (°dH).

1 drop = 1 German Hardness (°dH).

Hardness conversion factors

1 German Hardness (°dH) = 1.78 French Hardness (°fH) = 17.8 mg/L CaCO3

The Features of AQUAX®

Its provided with 50 mL Reagent (Hardness Indicator Buffer Solution) and test container in a box.

  • Wide application areas: all industries like textile, agriculture, laundries, aquarium, fishing, home and all areas wherever water hardness is important
  • 100 drops in One-Reagent 50 mL (Hardness Indicator Buffer Solution)
  • Measuring in German Hardness (easy convertible to French Hardness – look at hardness conversation factors above)
  • The amount of CaCO3 in the water could be calculated easily (look at hardness conversation factors above),
  • Test container with a tap provides easy and safe to use,
  • The easy drop-and-see application with One-Reagent provides reliable results within few seconds.

Shelf-life and storage

  • Store at 10 – 25°C to maintain top condition for 2 – 3 years
  • Close the Buffer Solution cap immediately after finish the test
  • Protect from direct sun light and moisture

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