Drinking water and water quality
The drinking water of those living in the Helsinki Metropolitan Area travels roughly 120 kilometres through a tunnel from Lake Päijänne to the HSY water treatment plants in Pitkäkoski and Vanhakaupunki in Helsinki.
The raw water taken from Lake Päijänne amounts to only one-hundredth of the lake’s natural discharge. Therefore, taking the water for Helsinki residents to use does not change the natural conditions on the shores of Lake Päijänne. The raw water is extracted from a depth of 26 m at a distance of 350 m from the shore. This keeps its temperature constant throughout the year, which is good for water quality and the condition of the water management network.
The water is treated at the water treatment plants in Pitkäkoski and Vanhakaupunki. The treatment process is a controlled ensemble of procedures monitored in a centralised manner.
The water treatment plants’ process laboratory and the health protection authority monitor water quality and make sure that it clearly fulfils the quality standards set forth in the Decree of the Ministry of Social Affairs and Health Relating to the Quality and Monitoring of Water Intended for Human Consumption (461/2000).
Vantaa gets over 90 per cent and Espoo about 65 per cent of its tap water from the Pitkäkoski water treatment plant. Kauniainen, in turn, receives all of its tap water from the Pitkäkoski plant. The tap water used by Helsinki residents is produced at the Vanhakaupunki and Pitkäkoski water treatment plants.
Additionally, domestic water for about 35 per cent of the residents of Espoo is produced at the Dämman surface water plant.
Roughly 6 per cent of the people living in Vantaa and 0.4 per cent of those living in Espoo use groundwater as their domestic water.