Scale Formation In Water Systems

As an Engineer or Facilities Manager, you probably know what scale is and you may have seen it on the

scale in water pipe

inside of old water pipes.




The water coming into your site from the mains supply contains minerals. How much and what type depends on the geology of the rocks the water passed through and over on its way to the mains water system. This means that the amount of minerals in the water (called the ‘hardness’ of the water) varies in different parts of the country.

There are many kinds of scale but the main one you need to know about is limescale (calcium carbonate). It forms when there is a high concentration of minerals in the water, and they come out of solution – which means they are no longer dissolved in the water. They then form the familiar deposit you have seen in the bottom of your kettle.


The obvious answer is redscale heat transfer graphuced flow rates which reduces efficiency, there may even be blockages.

Less obvious is a big reduction in heat transfer efficiency as the scale is thermally insulating as shown in the graph

This means higher costs in energy for your heating, chilled water system, cooling system or steam boiler. Systems can even fail completely because they overheat.




Another ‘hidden’ effect is the way scale becomes a great living space for bacteria in the system, which can bring a whole extra set of problems such as an increased risk of legionella, and corrosion.


Are you concerned that scale may be forming in your system – how do you know?

The obvious answer is to look at the inside of pipes and heat exchangers – not always practical of course! But you can test the water and do some simple calculations to tell you whether your water is likely to form scale. There are calculators to help.

If you have hard water, preventing it from forming scale in the first place is of course the best strategy and, in most cases, its surprisingly simple – you install a water softener.

water softenerThese come in lots of shapes and sizes from small domestic units to huge industrial systems, but they all work in a fairly simple way. They are usually very reliable and cost effective. Find out more here:





If a water softener isn’t the right solution for you – some clever chemistry can be used instead:

  • pH (acidity / alkalinity) – this can be controlled using chemical dosing to reduce scale formation.
  • Scale inhibitors – clever chemicals that can reduce scale formation.



  1. Find out whether you have (or soon will have) scale problems by inspecting the system and testing the water.
  2. Put the measures above in place in the right combination for your system.
  3. Congratulate yourself and enjoy the peace of mind!





If you have blockages and scale in your system right now – what can you do?

Firstly – DON’T PANIC, the right water treatment programme can get your system back in good health. Take it step by step:

  1. Take a methodical approach to make sure you fully understand the causes of the problem. You may need to spend some time on testing before you start taking action.
  2. Get the system under control with a planned approach and keep testing to make sure you are going in the right direction.
  3. Be prepared to invest some time and money to rectify the situation – keep in mind how much the scale is costing you!