This process combines chlorine and ammonia to safely disinfect your drinking water.

Mono-chloramination combines very small quantities of ammonia with chlorine, providing a safe means of disinfection for your drinking water. This is a useful process in supplies with very long pipe networks or that are prone to elevated levels of Trihalomethanes (THMs).

Safe and reliable

This form of disinfection has been used worldwide for over one hundred years. It is widely used by Scottish and English water utilities as a safe and reliable way to disinfect water. In Scotland more than one million consumers (25% of consumers) receive mono-chloraminated water.

This disinfection process is recognised by the EPA and the World Health Organisation (WHO) as a valid and safe treatment process for drinking water. Mono-chloraminated water is perfectly safe to use for bathing, drinking, cooking and all our everyday water uses. It can be safely consumed by children, pregnant women, those who are on low sodium diets, and people with diabetes. 

Use in water supplies

Chlorine is still the main disinfection used in the treatment of public water schemes in Ireland. There are a small amount of schemes with raw water sources that are high in colour and organics. The use of mono-chloramination in such supplies will help to eliminate problems with disinfection by-products such as THMs.

Changing a water supply

In advance of a change from chlorine to mono-chloramination, Irish Water, in conjunction with the local authority, may carry out scouring of pipes and reservoirs. During the changeover from a chlorinated to mono-chloraminated supply, customers may experience some taste and odour issues for a few weeks. Once the mono-chloraminated supply is established and in full operation, there should be no issues with taste and odour. 

Where a supply changes from standard chlorination to mono-chloramination, some adjustment may be required to equipment used by dialysis patients who use the water. Irish Water works directly with the HSE’s National Renal Office and registered home dialysis patients in this respect. There may also be some adjustment required to the neutralising agents used in fish tanks. 

Kidney dialysis patients

Where a proposed disinfectant change to mono-chloramine is planned, Irish Water will engage directly with the HSE in advance to determine if there are any dialysis patients being supplied from the scheme. We will also check our registered list of vulnerable customers. Any dialysis patients will be contacted directly in advance of any change to ensure they have the correct equipment and support. If any dialysis patients have concerns we would ask that they contact their doctor or their HSE Office for medical advice. Kidney dialysis patients can safely drink, cook and wash in mono-chloraminated water. 

Aquariums and aquatic pet species

As with chlorinated supplies, mono-chloramine may be harmful to fish kept as domestic pets in aquariums and fish tanks, and therefore it should be neutralised before use.  Neutralising chemicals are available from pet shops. For schemes where Irish Water is proposing the change to mono-chloramination we will inform pet shops in the supply area ahead of any changes to treatment. Please contact your local pet shop or aquarium for further information. 

Apart from aquatic pet species, mono-chloramination is not harmful to pets.


The introduction of mono-chloramination can slightly increase the corrosiveness of the water. In order to help prevent this, a food grade additive called orthophosphate is added to the water at the treatment plant. This is a common food additive found in many foods we consume every day such as milk, beer and soft drinks. Orthophosphate over time builds up a coating on the pipes which helps prevent corrosion. This coating is also effective in guarding against metals such as Lead, Copper and Nickel from dissolving into your drinking water from pipes and internal plumbing.