Ion Exchange Water Softeners

What is limescale? 

Limescale is a chalky white substance that coats the inside of pipes and appliances such as kettles. It is caused by the precipitation of minerals such as calcium and magnesium out of hard water.

Why is limescale a problem? 

Limescale causes a significant increase in energy input to the boiler to meet the same heat demand it will also insulate the water from the heat source and impair performance and heat transfer. Build-up of scale along with fluctuating temperatures encourages the growth of bacteria including Legionella and this could pose serious risk to the users of the system. 

Softened water will eliminate the build-up of limescale in pipes, on heating elements and at the outlets reducing maintenance/repair costs and improves efficiency.  

How do water softeners work? 

A water softener works by removing the magnesium and calcium present in your water supply through a process of ion exchange, turning it from hard water to softened water. 

Legislation 

The Health and Safety Executive’s Approved Code of Practice (ACoP) and Guidance document titled “Legionnaires’ disease: The control of legionella bacteria in water systems” (L8) gives practical advice on how to comply with UK health and safety law with respect to the control of Legionella bacteria.

HSG274 Part 2: The control of legionella bacteria in hot and cold-water systems 

2.8 The cleanliness of the system must be maintained, as legionella bacteria are more likely to grow in a system fouled by deposits. In hard water areas, softening of the cold water supply to the hot water distribution system should be considered to reduce the risk of scale being deposited at the base of the calorifier and heating coils, and to reduce the potential for scale build-up within the system pipework and components. 

2.72 Light scale formation on the inner surfaces of pipes can be protective against the leaching of metals such as lead or copper, but heavier deposits are likely in hard water areas. These deposits increase the surface area and therefore the potential for microbial colonisation (biofilm formation) and can provide protection from the effects of biocides.

In hard water areas, softening of the cold-water supply to the hot water system should be considered. This is to reduce the risk of scale being deposited at the base of the calorifier and heating coils, especially at temperatures greater than 60°C, and the potential for scale build-up within system pipework and components (e.g. TMVs) which may significantly reduce flow and adversely affect the efficiency of the system.

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