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Frequently Asked Questions

The following information may help you to diagnose problems that can sometimes be seen or tasted in tap water, and includes some simple checks or measures you can carry out.

If after reading this guidance you have any further questions or concerns, please contact us at the details below.

Why is my water brown, orange, or yellow?

The most common cause of brown/orange/yellow water is suspended particulate iron, which is dislodged from walls and floors of cast iron watermains. These deposits can become dislodged by hydraulic changes within the mains network (e.g. by vibration through the ground, use of hydrants or water supply interruptions) and become mobilised.

Typically the problem resolves within an hour or two when the disturbance has finished. 

 

Why is my water white?

White discolouration in water can be caused by either trapped air or dissolved minerals associated with water hardness

  • Air can be introduced into the water supply following repair work on the distribution network, or by a pocket of air becoming trapped in the internal domestic pipework. Aerated water has a cloudy or milky white appearance.
  • Dissolved minerals associated with water hardness arise from the natural minerals found in water precipitating out and forming a fine white sediment. The presence of suspended chalk has a powdery white appearance.

In each case, there is no risk to health although the appearance of the water may be unappealing.

To determine whether the cause is air or dissolved minerals the 'Glass Test' can be used:

  • Fill a glass with water from the cold kitchen tap and observe how it clears.
  • Aerated water can take up to ten minutes to clear, and will clear from the bottom of the glass upwards.
  • Water containing chalk takes an hour or more to clear, with the glass clearing from the top downwards.
  • A fine sediment will then be left on the floor of the glass.

Any white water in the mains network should clear within two to three hours. After this time the tap should be run for two to three minutes to check that the problem has cleared. When running the tap you can catch the water in a bucket or basin and use this water for any purpose other than drinking and cooking. However, if the problem persists please contact us for further advice.

 

Why is there a chlorine taste or odour from my water?

Chlorine is used in the treatment and distribution of drinking water as an anti-microbial disinfectant.

Chlorine has been used for many years as a disinfectant in the water industry to prevent the spread of infectious diseases, and has the added advantage that it remains effective from dosing right up to your tap.

The level of chlorine dosed into your drinking water is carefully controlled and monitored.

Drinking water treated with chlorine poses no risk to health, but if you are concerned about the taste then a good way to reduce this is to fill a jug with water and refrigerate it overnight.

The taste will disappear by morning as chlorine is released from the water.

It should be noted that water kept in this fashion should be treated as a perishable food and be consumed within 24 hours.

However if you do still have any concerns please contact us at the details below.

 

Why is there an earthy or musty taste from my water?

This is often caused by high numbers of harmless micro-organisms. Micro-organisms occur naturally in all waters and their numbers increase during the summer months. This growth can be a particular problem in domestic systems, especially if the water has been allowed to stagnate. In addition, the warming of cold domestic pipes by the hot water system can produce conditions favourable for microbial growth.

There are a number of strategies which can be used to alleviate this taste problem:

  • If the property has been unoccupied for some time then the cold kitchen tap should be flushed for approximately five minutes and then left to stand for one hour. When running the tap you can catch the water in a bucket or basin and use this water for any purpose other than drinking and cooking.
  • The proximity of hot domestic pipes to cold pipes should be checked, and appropriately lagged if necessary.

Note: Before tasting water it is a good idea to move the glass away from the sink. This will prevent odours from the sink / drain masking the taste and smell of the drinking water. 

 

What is water hardness?

Hardness is determined by the level of naturally occurring calcium and magnesium compounds a water contains.

  • Water with a high calcium and magnesium content are considered to be hard, and those waters with a low content are considered to be soft.
  • Water in Dublin City is rated as soft. The exceptions are some areas along the northside of the City, which are fed from Leixlip Water Treatment Plant.
  • Hard water is found in areas which have a chalk and limestone geology.
  • As water passes through the rock it picks up chalk carbonates, the concentrations of which will determine the level of hardness.

There is no health risk associated with hardness.

However, hard water can lead to scale formation and may also affect the appearance of hot drinks, increase soap consumption and reduce detergent efficiency.

If your internal domestic system contains either copper or lead pipes then the minerals in hard water can create an internal protective film.

This protective film can line the pipes and prevent the metals leaching into the drinking water supply.

If hardness scale becomes a problem there are a number of simple measures that can be taken to reduce the level of deposition:

  • Reducing the temperature of your hot water to 60°C or lower can decrease scale deposition.
  • A stainless steel wire scale collector placed in your kettle can reduce scale build-up.
  • In some types of plastic kettle the scale may not stick to the sides but float on the surface of the water. This can be avoided by regularly rinsing the kettle.
  • Follow the manufacturer’s instructions for any appliances that use water.

 

Why is fluoride added to water?

Fluoride occurs naturally in soils and rocks and can therefore be found in raw water.

The concentration of fluoride depends on the type of soil and rock the water passes through.

Fluoride levels in drinking water of 0.6-0.8 mg/l are considered to have health benefits by reducing the incidence of tooth decay.

The decision to fluoridate water supplies is taken by Department of Health and Children under the  Fluoridation of Water Supplies Regulations 2007 (S.I. No. 42 of 2007) and European Communities (Drinking Water) (No.2) Regulations, 2007 (S.I. 278 of 2007).

 

What is cryptosporidium?

Cryptosporidium is the name given to a type of protozoan parasite which can infect humans and animals.

These parasites can be found in the faecal material of infected humans and animals and can survive in the environment for several months.

Infection with Cryptosporidium arises by ingesting the parasite. Common transmission routes include:

  • Contact with infected animals (particularly cattle and sheep).
  • Ingesting contaminated food and water especially abroad
  • Person-to-person spread (particularly within families/households).
  • Swimming pools in this country and abroad.
  • Other recreational waters (e.g. boating lakes, rivers).
  • Nappy changing facilities e.g. creches

Infection with this organism is called cryptosporidiosis and symptoms can persist for several weeks.

In healthy people the infection is usually self-limiting, but in immunocompromised people (e.g. people with a suppressed immune system such as AIDS patients or transplant recipients), the elderly, pregnant women and children the infection is more serious and can be life threatening.

Please consult a doctor for any medical advice relating to these issues.

Under normal operating conditions Cryptosporidium is removed by effective water treatment, principally by coagulation and filtration.

However, due to the parasites' small size and inherent resistance to chlorine, there exists a small potential that the organism could penetrate the multiple treatment barriers set in place to remove it.
 

Why are there insects and aquatic invertebrates in my water?

Insects and aquatic invertebrates can inhabit raw waters that are used for drinking water supplies.

Generally these organisms are removed following effective treatment before the water is dispatched into supply.

However, aquatic invertebrates and insects could enter the distribution network if the network has become compromised.

These organisms can also be found in domestic cisterns which are improperly sealed/installed and can also crawl into tap spouts.

If insects / aquatic invertebrates are discovered in the mains drinking water, flush the cold kitchen tap for five minutes. When running the tap you can catch the water in a bucket or basin and use this water for any purpose other than drinking and cooking. However, if the problem persists please contact us for further advice.

If the problem persists please contact us.

For more information

Water Services Division
Dublin City Council
Marrowbone Lane
Dublin 8

Tel: (01) 222 0600
Fax: (01) 453 4849
Email: customerservices@dublincity.ie