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 

Drinking water can be classified as soft or hard and water hardness is determined by the level of naturally occurring calcium and magnesium compounds in your water. High content classifies your water as hard. Low traces of the compounds make your water soft. Hardness is generally determined by the route water takes to your tap and the geology of the area your drinking water comes from.

Rainwater is naturally soft and when it passes through porous rocks, calcium and magnesium compounds in the rocks slowly dissolve into it forming hard water. If rainwater passes over less porous rock it does not pick up as many mineral particles and remains soft. This is the case in the Isle of Man where raw water collects in reservoirs which keep the water naturally soft. After the treatment process Manx drinking water remains soft at around 40 mg CaCO3/l total hardness (16 mg Ca/l).

There are no health based guidelines or standard limits for water hardness. The operating instructions for some domestic appliances, particularly dishwashers, refer to water hardness and manufacturers describe water hardness in different ways.

The hardness conversion factors table below may help you:

Mg Ca/l

Mg CaCO3/l

Clark Degrees

French Degrees

German Degrees


0 - 40

0 - 100

0 - 7

0 - 10

0 – 5.6