What is limescale?
The municipal water supplied to approximately 65% of the UK population is hard water, containing natural calcium and magnesium mineral salts. Although these minerals are not harmful when we drink them, they can cause harmful scale and deposits in pipes and appliances.
When hard water is heated, these dissolved salts can separate out, clinging to the nearby surfaces and forming a head layer of scale. In pipes, this layer of limescale slows down the flow of water and may eventually block the pipe completely. In boilers, washing machines, kettles and other appliances, it builds up on the heating elements or heat exchangers, reducing efficiency and shortening the useful life of the equipment.
Also, limescale settling out from the hard water will often lead to deposits around taps and showers which can be difficult to remove.
Where is hard water in the UK?
How is hard water measured?
Hard water is measured by the amount of calcium and magnesium salts in your water. This is expressed in the UK as parts per million (ppm) as follows
| Soft |
0-50 ppm |
| Moderately Soft |
50-100 ppm |
| Slightly Hard |
100-150 ppm |
| Moderately Hard |
150-200 ppm |
| Hard |
200-300 ppm |
| Very Hard |
200-300 ppm |
If total water hardness exceeds 200 ppm steps should be taken to treat the feed water to water heaters and the hot water circuit of combi boilers to reduce the rate of accumulation of limescale – in accordance with Part L Building Compliance Guidelines.
How do I know how hard my water is?
In terms of measurement your water provider will advise how hard your supply is or you could use a simple colour test strip. These are available through plumber's merchants. The most visible sign in your household is usually the kettle where you would see clumps of scale in the water or baked onto the element.
What Does SESI do?
The SESI electrolytic scale inhibitor prevents limescale in water, particularly useful in hard water areas. The SESI can help prolong the life of appliances and prevent pipes from being blocked.
SESI works by electrolytic action. This involves the interaction of two metals in the unit, the copper body (cathode) and the zinc (anode). It has the effect of releasing zinc irons into the water which change the structure of the hard salt crystals (calcium) that cause scaling. This causes the crystals to cling to each other rather than appliances or pipes. They are simply flushed through the system or simply wiped away.
What is the difference between electrolytic and magnetic devices?
Magnetic devices are claimed to prevent scale on an individual appliance such as a washing machine, dishwasher, coffee machine, vending machine etc. Though they are environmentally friendly, non-polluting and easily connected to the incoming mains water pipe, their effectiveness has not been scientifically proven. The magnetic device cannot be used to treat the whole house, nor for stored water and will not stop scale in static situations such as a boiling kettle.
The unit should be installed in the rising main of the municipal water supply, so that the whole property is protected. If the device is fitted to protect only a single appliance, there should be at least three metres of water pipe between the SESI unit and the appliance.
For more information on Salamander products please visit the Salamander Engineering website.