Water and wastewater services for Kent, Sussex, Hampshire and the Isle of Wight
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Turbidity FAQs

Turbidity is a term used to describe how clear water is. In simple terms it is a measurement of the water’s "muddiness" or “cloudiness”.

  1. What causes turbidity? 
    • Water, like any fluid, contains tiny suspended particles of many different sizes that are invisible to the naked eye. While some will be large enough and heavy enough to settle rapidly to the bottom of a glass or container, other very small particles will not.

      These small solid particles cause the liquid to appear cloudy. The general rule is the cloudier the water, the greater the levels of turbidity.
  2. Why is this a problem? 
    • The measurement of how cloudy water is, is one of the key tests to determine the overall quality of water supplies. Cloudy water caused by tiny suspended particles itself is not a major health concern.

      However, high levels of turbidity can sometimes interfere with the disinfection process that we use to make customers’ tap water safe on the long journey from our treatment works to their tap.

      The tiny suspended particles can sometimes shield viruses and bacteria which would normally be destroyed by the disinfectant.

      All our drinking water supplies are routinely treated and tested for turbidity before it leaves a water treatment works. However. treated water can still pick up tiny particles, such as iron deposits.
  3. Is turbidity unusual or unnatural? 
    • Increased turbidity can be caused by natural events such as storms, heavy rains and floods, which create fast running water that can carry more particles and larger-sized sediment.

      This increased flow can pick up sand, silt, clay, and organic particles from the land and carry it to surface waters – rivers and reservoirs – from where we abstract customers’ water supplies.
  4. How is turbidity measured? 
    • Turbidity is measured by a special piece of equipment called a Nephelometer, which then translates readings into Nephelometric Turbidity Units or NTUs.

      The water quality standard that we must comply with for Turbidity is 1 NTU.
  5. What if I have been told to boil my water? 
    • If you have been asked to boil your water, it is recommended you follow these guidelines:

      Boiling the water – using an electric kettle is better and safer than using pots and pans on the stove or hob. The water does not have to be held at boiling point for any length of time – all you need to do is bring the water to the boil in the kettle.

      Keep any kettle lid on and allow the water inside the kettle to cool naturally before using it, for either cooking or drinking. If there’s any left over, you can keep it in a clean container for the fridge for up to 48 hours.

      Storage – Do not store large quantities of boiled water in open containers, such as buckets or bins, as the water may deteriorate or become contaminated if it’s left for long periods of time.

      Brushing teeth – use cooled boiled water from your kettle to brush teeth.

      Ice cubes – if you made ice cubes prior to getting the boil water notice, then discard them and wash the ice trays as normal. Make new ice cubes with cooled boiled water.

      Personal washing and bathing – it is quite safe to wash and take a bath as normal; the infection is transmitted by swallowing the water.

      Washing up – dishes should be washed using boiled water if possible. Dishwasher can be used provided they are set on a hot cycle wash.

      Hot tap water - water from the hot tap is NOT suitable for drinking.
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