Hard water and soft water – what do these terms mean and how so they differ? When rain falls from the sky it contains very few dissolved chemicals. However, when it hits the ground, and especially when it moves through rocks and soil, it picks up elements which changes some of the properties of the water. These properties can be in part beneficial…but can also lead to problems, especially to pipes and equipment.
Hard water and soft water – A little chemistry
Our entire planet is made up of chemicals called compounds. Each compound is normally a combination of two or more elements joined (bonded) together. Some of these compounds break down easily, especially in the presence of water and these are often referred to collectively as “salts”. Other compounds don’t break down readily in water. When a compound breaks down it can release elements into the environment in the form of ions. Ions are elements with a “charge” and it’s this charge that can bond elements together.
Common salt, for example, is a compound made up of just two elements: sodium (whose chemical symbol is Na) and chlorine (whose chemical symbol is Cl). In water, the salt compound breaks up into sodium ions (Na+) and chlorine ions (Cl-). The little + and – signs show that each ion has a slight charge. Some ions have multiple charges…like iron, magnesium, calcium, manganese etc. Many of these ions will react with other elements in the environment, forming new compounds. Rust and scale in pipes, for example are examples of where these compounds have been deposited out of the water that flows through the pipes.
When water picks up dissolved amounts of calcium (Ca++) and or magnesium (Mg++) it is said to become hard water. Calcium and magnesium are found naturally in rock forming compounds (geologist call them minerals) which breakdown over time releasing the ions. These two ions then can react with other metals (iron or copper pipes) and create a coating or scale. Eventually the entire inner part of the pipe can become clogged. These ions also react with soap stopping it from becoming frothy. Instead the ions attach to the soap compounds and form a scum. With detergents (compounds slightly different from soup) you can still get the water to froth.
Some hard water is thought to be good for you as it can contain ions that are needed or good Heath. These “mineral waters” can be bottled and some sold for premium prices.
Most hard water however has more hassles than help. The clogging of pipes, the lousy way soap performs and the scaling up of furnaces makes people want to try and “soften” the water. To do so the dissolved calcium and magnesium has to be removed. There is a number of systems that do this, but most work using the same chemical principle. If you force hard water through a pile of common salt or other compound containing sodium salts, the calcium and magnesium get replaced in the water by the sodium. This reduces the hardness. It also changes the taste of the water – some people say the water becomes salty to taste (I don’t fine it that strong).
If you are looking for ways to help out with hard water issues – see this excellent summary.
Naturally soft water water contains no calcium or magnesium ions and only sodium ions. Sometimes these soft waters can become “salty” . These waters can be changed by adding calcium and magnesium ions to make it harder. Some folks use a reverse osmosis system to remove the salt. In these systems water is pumped through a thin walled bag which allows water to pass through and not the salt. Large scale reverse osmosis systems are used to turn sea water into drinking water.
Very few people have perfect water and so most of us have to work at either living with our local water, or install some system to bring it closer to what we are happy to live with. Understanding the chemistry will help you to understand what system you might need.
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