Cryptosporidium and Giardia detections

Cryptosporidium and Giardia are parasites that are found in human or animal waste and, if they are present in drinking water, can cause persistent diarrhoea.

The Drinking Water Regulations do not explicitly require Cryptosporidium or Giardia monitoring to be carried out; but because of the risk to health from these parasites, the EPA has requested Irish Water to test for them.

Irish Water is required to assess all water supply sources across the country and determine if there is a risk that the raw water could have Cryptosporidium or Giardia present. If either parasite might be present in a supply, then appropriate treatment processes (referred to as a ‘barrier’) must be put in place.

Cryptosporidium and Giardia may be detected in treated water where:

• There is no treatment barrier in place at the water treatment plant;

• The treatment barrier is not being properly operated, controlled or maintained.

When Cryptosporidium or Giardia detections are reported, the EPA ensures that Irish Water carries out investigations into the cause; takes corrective action; and consults with the Health Service Executive regarding the risk to public health. If the Health Service Executive is concerned that using the water might endanger people’s health, Irish Water will issue a boil water notice for the supply.

The EPA may also carry out audits of treatment plants to see if further action is necessary. If the EPA is concerned about a supply not having a treatment barrier or a treatment barrier not performing adequately, it will add that supply to the EPA Remedial Action List. Once a supply is added to the Remedial Action List, Irish Water must provide the EPA with an action plan and prioritise that supply for improvement.

Note: Clonmel Poulavanogue supply has been on the Remedial Action List since 2008

Note: There are supplies where treatment barriers are not being operated, controlled or maintained adequately. For example, operational issues at Leixlip Water Treatment plant meant that the treatment barrier for Cryptosporidium was compromised and this led to two boil notices on the supply in 2019.

Water Restrictions

A water restriction means that people are advised not to use the water for drinking and are advised to use an alternative source of water, such as bottled water, or tankered water which must be boiled to make it safe before consuming.

For example, in Bailieborough, Cavan, elevated levels of manganese in the raw water source and issues at the water treatment plant resulted in 7,785 residents being advised not to consume the water for 11 days in 2019. An EPA audit at Bailieborough identified significant issues and many contributory factors which led to the need to place a restriction on the supply.

The supply affected is Ballydermody, Waterford, which has been on a water restriction since 2013 due to high levels of nitrate.

Irish Water disputes that it has responsibility for this supply

Boil Water Notices

A Boil Water Notice is a formal notice issued to all properties in an area advising that drinking water from the public mains is not safe to drink unless it is boiled and cooled beforehand.

Irish Water will only issue a Boil Water Notice after consulting with the Health Service Executive (HSE) , the statutory authority on public health matters.

The most common reason for issuing a Boil Water Notice would be where routine testing of the drinking water supply has shown the presence of harmful bacteria (such as E. coli), or pathogens such as Cryptosporidium.

In some cases a Boil Water Notice may be imposed where there is a risk of contamination but where test results are yet to be confirmed. An example might include where the disinfection system has failed, or where a pollution event has occurred in the vicinity of the source water. In these cases it is prudent to protect public health by issuing a Boil Water Notice rather than wait for test results to confirm the risk.

The EPA is the drinking water quality regulator for public water supplies, so Irish Water is required to notify the EPA of all boil water notices affecting public water supplies.

EPA publish summary information and commentary on boil water notices in their annual Drinking Water Reports

EPA are due to publish the Drinking Water Report for 2020 in the coming weeks, but you can find the most recent published data in 2019 Report here Drinking Water Report (

The following sections of the report are worth a look

Appendix 3: Boil Notices and Water Restriction Notices in place on public water supplies during 2019

Pages 9 – 11: EPA commentary on boil water notices

During 2019, 67 boil notices were in place in 16 counties affecting 695,364 consumers. This is a significant increase compared to 2018, during which 44 boil notices were in place in 14 counties affecting 97,204 consumers.

The main reasons for the increase are:

• Two boil notices were placed on the supplies served by Leixlip water treatment plant in October and November 2019, affecting a total of 657,3959 people; and

• 38 notices were placed on 37 supplies (two on the South Regional supply in Wexford) throughout 2019, following checks by Irish Water which found that these supplies were not being fully disinfected. These notices affected 1,341 people in small areas across the 37 supplies.

At the end of 2019, 21 boil notices were in place affecting 14,632 people. This is in comparison to the 10 boil notices affecting 897 people at the end of 2018. The main reason for the increase in the number of people affected is that the Lough Talt supply in Sligo went back on a boil notice in January 2019, having had a previous notice lifted at the end of 2018.

The EPA monitors the progress Irish Water makes to fix the problems at supplies with boil notices and makes sure that the notices are in place for the minimum amount of time.

Of the 67 boil notices in 2019:

• Eight were short-term notices (less than 30 days’ duration), compared with 26 in 2018. These include two notices placed on the supplies served by Leixlip water treatment plant;

• The remaining 59 were in place for longer than 30 days (long term Boil Water Notices);

Of the 38 notices in 2019 placed on supplies which were not being fully disinfected, 23 were in place for more than three months but less than six months;

• Six notices were in place for longer than one year. Of these six:
o Two notices were lifted in 2019 (Kilconnell, Galway and Kilsellagh, Sligo);
o One from October 2018 remained in place (Clonmel-Poulavanogue, Tipperary); and
o The other three have been in place for more than five years. One supply (Scrothea, Waterford) has since had works completed and the notice lifted. Irish Water dispute that they are responsible for the other two supplies. The EPA is pursuing this matter with
Irish Water and the relevant local authorities.

While there has been a reduction in the number of short-term notices, Irish Water did address the issue of inadequate disinfection at most of the affected supplies in 2019. EPA is concerned at the overall trends. The 2020 data is out very soon.

Trends in Boil Water Notices from 2017 to 2019

Current Boil Notices are available here (filter category by Boil Water Notice)


There appears to be no public database on boil water notices, to allow user to see historically which areas and which treatment plants are regularly subject to boil notices, whether the reasons for notices are constant or change, how long the notices are in force, what is the timelines between notices, which sites are most impacted by notices, and what measures are being taken to address the ‘issues.’ Reasons for boil water notices are not listed in detail. Details of treatment failures are released in more general terms, on the IrishWater website.


“water supply served by the Macroom Public Water Supply is potentially unsafe to drink due to increased turbidity at the water treatment plant”

“due to issues at the water treatment plant which has affected the disinfection process” Wexford

“Due to issues at the water treatment plant which may have compromised water quality” Borris, Carlow

“water supply served by the Ballyheigue Public Water Supply and associated Clanmaurice Public Group Water Supply is potentially unsafe to drink due to the detection of Cryptosporidium on the supply”

“water supply in the Glenamaddy area that is served by the Glenamaddy Public Water Supply is at risk due to the deterioration in raw water quality entering the plant”

Overall transparency is low, EPA data is published up to two years in arrears, and there is a piece of work needed to identify the paperwork behind each Boil Notice.