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What is water hardness?

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190 views asked Apr 6, 2015 by Matt Hall

3 Answers

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Water in nature is never really pure, even when it falls from the clouds in its purest natural state, it contains some dissolved dust and gases as well as some suspended matters. After it has run over the surface of the ground or percolated through the rock layers, its impurities have greatly increased because water is practically a universal solvent and dissolves some of everything it touches. Therefore it needs refining or conditioning before using for domestic or industrial service. There are two general classes of water:

  1. Surface water such as:
    1. Brooks.
    2. Creeks
    3. Streams and rivers
    4. Ponds, reservoirs and lakes
  2. Ground water such as:
    1. Spring waters
    2. Shallow well waters
    3. Deep well waters
    4. Mine waters

The present in water are:

  • Dissolved solids
    1. Scale and deposit formers which cause total hardness, calcium, magnesium, alkalinity, sulfate, silica, iron, manganese.
    2. Corrosives includes chloride, sodium, total dissolved solids.
  • Dissolved gases
    1. Corrosives such as oxygen (from air), carbon dioxide, hydrogen sulfide.
    2. Inert such as nitrogen.
  • Suspended solids
    1. Turbidity, sediment, color, algae, bacteria, sand.

Effects of Water Conditions on Operation:

  • Corrosion which causes:
    1. Leaks
    2. Poor flow caused by tuberculation
    3. Rusty water and stains (Iron, Steel)
    4. Blue-green stains (Copper)
  • Scale formation – usually calcium carbonate:  

Calcium carbonate is less soluble in hot water than in cold. The water tendency will increase in higher calcium, alkalinity, PH, total dissolved solids and temperature (Langelier Index). Scale reduces heat transfer (hot water generators, boilers, refrigerant condensers), reduces flow through pipes and interferes with operation of mixing valves, flushometers, and shower heads.

  • Sediment accumulation:

Scale can build up by:

  1. Iron and manganese oxides (usually in private well waters).
  2. Fine sand (well waters)
  3. Rust – from mains (disturbances – fires, construction).
  4. Algae – from reservoirs (common with unfiltered supplies)
  5. Sediments, fly ash, micro-organisms from air contact in cooling towers, etc.
answered Apr 6, 2015 by Matt Hall
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Water hardness is the amount of dissolved calcium and magnesium in water. Water hardness is high in dissolved minerals,both in calcium and magnesium
answered Aug 7, 2015 by Joe ifeanyi
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Water hardness is mainly because of calcium & magnesium in the water.This hardness is usually measured as ppm(parts per million),milligrams per litre(mg/l) grains per gallon.Water in the purest form when undergoes percolation through limestone and chalk ,which are rich in calcium and magnesium turns to hard water.Hard water for drinking is not preferable.

There are two typesof hard water i.e Temporary hardness ,Permanent hardness

Temporary hardness is due to the pesence of bicarbonate of calcium and magnesium.this harness can be removed by boiling water or by the addition of lime(which is rich in calcium hydroxide).In the process of heating the bicarbonates gets converted into carbonates,precipitates calcium carbonate leaving behind the soft water.

Permanent hardness is due to the sulphates of calcium and magnesium.This hardness cannot be removed by boiling.Treating is to be carried out to remove hardness.

(This is brief explaination,if needed i can explain in detail)

answered Aug 14, 2015 by sahana

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