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What's in our drinking water?

Our aim is to provide quality drinking water to the Island's population. To find out more about what's in our water you can read our latest Drinking-water Quality Report. Water quality for your area can be supplied on request. If you would like this information please contact us.

Drinking water contains a number of harmless substances. Some of these are naturally occurring, some are added in the treatment process and some increase slightly as the water passes through pipework. None of the water we supply is artificially fluoridated. Find out more about fluoride here. 

There are three substances of which we are often asked about, including why they are in water and how they are managed:

Hardness of our drinking water 

Water hardness is a measure of the amount of calcium and magnesium salts in drinking water. The Isle of Man has soft water; treated water leaves the treatment works on average at 40 mg/l (total hardness as CaCO3 mg/l). 

The operating instructions for some domestic appliances, particularly dishwashers, refer to water hardness. Domestic appliance manufacturers describe water hardness in different ways. The hardness conversion factors table below may help you.

Water hardness conversion (soft water)

Total hardness as 
Ca mg/l
Hardness as CaCO3 mg/l DH
(German degrees)
(French degrees)
Clark degrees mmol1
0-40 0-100 0-5.6 0-10 0-7 1

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