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The safety of our water

The addition of chlorine, in a variety of forms, is used widely around the world for the disinfection of public water supplies. It is very effective in killing a wide range of bacteria and viruses and the use of it, combined with filtration, is considered by public health bodies to have made a significant contribution to public health and near elimination of diseases such as cholera and typhoid.

Chlorine has been used on the Isle of Man for many years to disinfectant the drinking water. When the new Water Treatment works at Sulby and Douglas were designed in the early 2000’s, the Isle of Man Water Authority made a decision to continue to adopt chlorine addition as its method of disinfection and we continue to enjoy the benefits today.

A downside of the use of chlorine is that some people can detect a taste from the residual amount of chlorine that stays in the water. We have more information about that here.

Effects on our health

Typically, the amount of chlorine in the drinking water leaving our water treatment works is around 0.8 milligrams per litre (mg/l) and because chlorine naturally decays levels of 0.2mg/l to 0.8mg/l can be expected to be in the water that we distribute.

It is accepted that this level of chlorine does not have any detrimental effect on health. In fact, the World Health Organisation has suggested a guideline value of 5.0mg/l (around 10 times the amount expected to be in our water) for lifetime exposure to chlorine in drinking water.

The chlorination process

The need to ensure that your drinking water is free from harmful bacteria and viruses at all times is of paramount concern to us. We achieve this by filtering the water and then adding chlorine (in the form of sodium hypochlorite) to the water just before it leaves the water treatment works.

The chlorine is added by accurate dosing pumps and validated by a sophisticated monitoring and control system. We vary the concentration to ensure adequate levels remain in the water mains and service reservoirs to maintain quality up to the point of your tap.

Taste tips

Some customers who receive a supply shortly after it leaves the water treatment works may notice a stronger smell and taste of chlorine in their drinking water. Those at the end of the supply system are unlikely to be similarly affected as the chlorine levels naturally reduce as it makes its way through the mains network system.

Some people have a delicate palate and can taste chlorine when others cannot. Some people can taste chlorine at very low concentrations.

The best tips to ensure taste free water are;

1)    For tea and coffee try using freshly drawn cold water to fill your kettle

2)    Don’t re-boil the same water in the kettle

3)    For drinking water directly it often helps to cool some water in a clean container in the fridge and use this for drinking

Keep in mind that it is better to have water with chlorine in it, as at least this way we know we are protected from bacteria and the water is safe to drink.

In conclusion

Always use freshly drawn water for drinking or cooking, taking it from a cold tap supplied directly off the water mains, for example, the cold tap in your kitchen.

  • If water has not been used in the house for several hours (i.e. overnight or after a holiday), it is wise to draw off a washing up bowl full before taking water for drinking. This will ensure that you do not drink water which may have been standing for a long time in your pipework. There is no need to waste water as you can use it for other things such as watering plants.
  • If there is a slight smell or taste of chlorine that you do not like, place a covered jug of water in the fridge until it is cool. It will then be fine for drinking.
  • Do not use water from a hot water system or from your bathroom taps for drinking or cooking because it may come from a storage tank in the loft and may not be as fresh or safe as water directly from the cold tap.
  • If you notice a particularly bad or strong smell or taste which means you cannot drink the water, or you notice a different smell or taste for the first time you should contact us.
  • The level of chlorine in your home should be relatively stable (it does not alter very often). Sometimes we change around the water network system to carry out essential maintenance and you might receive a lower/higher level for a short period.
  • Sometimes we perceive changes in chlorine level (by taste) but normally this is a perception and probably not a real change. Our perception of chlorine taste is very complex and can be effected by other factors like the time of day, when (and what) we have eaten or drank.

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