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Problems of limescale

Heat - Problem of limescaleHard water

Water performs many vital functions, but not all its features are equally beneficial in all applications.

Water that is naturally hard, as in 70% of the UK and most other countries, contains dissolved calcium and other minerals. These help to build and maintain healthy bodies, but their effect on pipework and water systems can be disastrous.
When water-borne minerals, such as calcium bicarbonate, revert to their solid carbonate state, limescale is formed in water systems and this narrows pipes, blocks jets, slows the flow, reduces thermal efficiency and provides a breeding ground for bacteria.

Research has shown that just 6 mm of limescale can reduce energy efficiency by a staggering 40%, and, in a moderately hard water area, 6 mm of limescale can form in pipework, or on heat exchangers in just 2 years.  This in turn results in higher running costs. Billions of pounds are wasted every year in increased energy bills, lost production and early renewal of capital equipment.

Increased boiler time, due to scale

With no scale on its heat exchanger, a domestic hot water cylinder takes 1.5 hours to heat up.

With just 5 mm of scale the boiler has to run for over 4 hours wasting over 2.5 hours of fuel.

Source: University of Portsmouth

Safety considerations

Bacteria, including Legionella Pneumophila, proliferate in water systems with even moderate amounts of scaling, particularly in systems where scale prevents water reaching sufficient temperature to act as a biocide.
Isolation valves are often impossible to close due to scaling.  Safety or pressure relief valves often stick due to scale.

The chemical solution

The traditional solution to the problem of limescale has been the use of chemicals to prevent or remove scale, and to control the bacteria that thrive because of it. The use of chemicals, however, can cause or increase corrosion and create further environmental problems. It is also expensive. Descaling alone is estimated to cost industry in the United Kingdom around £1 billion a year.

The alternative to chemicals

Over the years many methods of physical water treatment have been tried. For example, placing alternate magnetic poles in parallel to flowing water induces a voltage in the water.  The frequency of the voltage is dependent on the velocity of the flow. If the frequency happens to be correct for the given conditions, precipitation occurs and the resultant crystals remain in suspension in the water.  The drawback with this method is that the frequency required varies according to the conditions in the water system e.g. flow-rate, water quality, temperature, pH etc. Therefore the results will be inconsistent, and this is the reason why Physical Water Treatment failed to gain wide acceptance.


In 1989, however, a new form of Physical Water Treatment was patented that did not involve magnets, chemicals, acids or expensive softening equipment, but achieved predictable and consistent results – the Frequency Modulated (FM) Electronic Descaler.