Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

Search is the most efficient way to navigate the Engineering ToolBox!

Soft or Hard Water

Sponsored Links

"Hard water" is water containing a quantity of dissolved minerals. Water hardness is a function of the amount of dissolved calcium and magnesium salts, iron and aluminum.

Total hardness can be calculated as

Total hardness in ppm Carbonate  =

   2.497 ppm Calcium

    + 4.115 ppm Magnesium

    + 1.792 ppm Iron

    + 1.822 ppm Manganese

The salts occur in a variety of forms where typically calcium and magnesium bicarbonates are referred to as "temporary hardness", and sulfates and chlorides are referred to as "permanent hardness".

When hard water is heated the carbonates precipitate out of solution, forming scale on the heat surfaces.

Soap is less effective and prevented from lathering in hard water because its reacts to form calcium or magnesium salt from the organic acids of the soap.

"Soft water" is treated water where the only cation (the positively charged ion) is sodium.

Soft or Hard Water - Dissolved Calcium and Magnesium
Water Hardness Classification1)Milligrams per Liter
(mg/L)
Grains per US Gallon
(gpg)
Soft 0 - 60 0 - 3.5
Moderate 61 - 120 3.5 - 7
Hard 121 - 180 7 - 10.5
Very Hard > 180 > 10.5

1) United States Geological Survey

  • 1 mg/L = 1 ppm
  • 1 ppm = 0.058 grains/US gallon
  • 1 ppm = 0.07 Clark degrees
  • 1 ppm = 0.1 French degrees

Hard water can be softened by passing it over an ion exchange resin.

  • zeolite processes for home water softeners
  • soda ash process for larger water softeners

 

Sponsored Links

Related Topics

Material Properties

Properties of gases, fluids and solids. Densities, specific heats, viscosities and more.

Steam and Condensate

Design of steam & condensate systems with properties, capacities, sizing of pipe lines, system configuration and more.

Related Documents

Boiler Water - Total Dissolved Solids (TDS)

Impurities from the feedwater will concentrate in the boiling water.

Domestic Water Supply - Lime Deposits

Lime deposited vs. temperature and water consumption.

Ice and Water - Melting Points vs. Pressure

Online calculator, figures and tables with melting points of ice to water at pressures ranging from 0 to 29000 psia (0 to 2000 bara). Temperature given as °C, °F, K and °R.

Oxygen - Solubility in Fresh and Sea Water vs. Temperature

Solubility of oxygen in equilibration with air in fresh water and seawater (salt water) - pressures ranging 1 - 4 bar abs.

Parts per Million - ppm

ppm - or parts per million - is commonly used as a unit of concentration.

Salinity of Water

Salinity - salt content - of fresh, brackish and sea water.

Water - Thermophysical Properties

Thermal properties of water at different temperatures like density, freezing temperature, boiling temperature, latent heat of melting, latent heat of evaporation, critical temperature and more.

Water - Thermophysical Properties

Thermal properties of water at different temperatures like density, freezing temperature, boiling temperature, latent heat of melting, latent heat of evaporation, critical temperature and more.

Sponsored Links

Search Engineering ToolBox

Search is the most efficient way to navigate the Engineering ToolBox!

SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!

Privacy

We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics on the AMP pages. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.