How is water treated?

Printer-friendly version


Water is supplied in Dublin on a Regional basis. The Region includes all of Dublin City and County and parts of Wicklow and Kildare. On a typical day 540 million litres of water is collected from our rivers, cleaned and made safe to drink at four main treatment plants. Three of these treatment plants are operated by Dublin City Council on behalf of Irish Water at Ballymore Eustace (Liffey), Roundwood (Vartry) and Ballyboden (Dodder). Fingal County Council operates the treatment plant at Leixlip (Liffey) on behalf of Irish Water.

Water treatment removes contaminants from raw water, which in the case of the Dublin Region is mostly river water, and makes the water safe to drink. Without water treatment the raw water would be unsuitable for human consumption as it may cause illness.

Even though all the water that leaves the water treatment plants is fit for human consumption only about 1% of it is used for that purpose. The remaining water is used for showering, flushing, watering plants etc. For that reason we ask you to be extra vigilant and conserve water where possible.

The treatment process

While every water treatment plant is operated differently the four main steps are generally the same:

  • Coagulation
    Water taken from rivers is screened at intake points to catch floating debris. Alum is then added, which forms tiny, sticky particle, which slowly gather removing colour and suspended dirt. This is known as coagulation.
  • Sedimentation
    The dirt and alum known as floc become heavy and sink to the bottom of the tank. This is known as sedimentation.
  • Filtration
    The clear water at the top of the sedimentation tank is then passed through filters, which are made of sand and gravel, and remove any remaining suspended matter. This is known as filtration.
  • Chlorination
    Chlorine is added to kill any remaining germs. A small residual amount of chlorine is generally present in the treated water that reaches your tap. This is to ensure that the quality of the drinking water is maintained through the pipe network.

Once water is treated it has to be delivered to the Region’s 1.5 million customers through a series of service reservoirs and a network of 7,200km of underground pipes, of which over 2,400km are in the City. Most of the water is gravity fed however in some elevated areas pumping is required. Levels in the service reservoirs generally drop during the day as demand is at its highest. The reservoirs are replenished at night time when demand is low.

Water Treatment Plants have a limited capacity. If we use more water than we can treat on any given day our storage levels will drop as the Water Treatment will not be able to provide sufficient water to replenish stores at night time.

For more information

Irish Water Contact Details:

Twitter:  @IrishWater
Telephone: 1850 278 278 (LoCall)
Minicom:  1850 378 378
(For hearing impaired customers with minicom equipment)
Postal Address: Irish Water, PO Box 860, South City Delivery Office, Cork City

To report an issue on Water Services please contact IW (Abtran) directly on 1890 278 278 (LoCall)

Please continue to contact Dublin City Council for information or issues relating to business account queries, surface water drainage and flood management.