Individual numeric measurements from 2021–2025. Text-only and censored results are retained in the history JSON and are not plotted as numbers.
Open this chart to load the measurements.
Numeric resultEPA-listed exceedance
Letterkenny Tap Water Quality
EPA monitoring records for Water Supply Zones mapped to Letterkenny contain 1,361 monitoring results across 69 parameters in 2025.
The separate EPA exceedance dataset contains 3 listed exceedance records across 2 parameters.
The most frequently listed were Colour (2) and Iron (1).
These are historical monitoring records and do not confirm the current status of water at a specific address. Current notices are maintained by Uisce Éireann.
- Latest monitoring year
- 2025
- Page updated
- September 2026
- Water Supply Zones
- 3
Monitoring results apply to the Water Supply Zones as a whole and may include sampling locations outside Letterkenny.
Selected monitoring data
Key drinking water parameters
Parameters are shown when measurements are available. Text-only and censored values remain unchanged in the detailed history.
Lead
2025 median3
2025 maximum3
Measurements in 20259
0 EPA-listed exceedances in 2025.
View parameter history
Nitrate
2025 median—
2025 maximum—
Measurements in 20259
0 EPA-listed exceedances in 2025.
View parameter history
Individual numeric measurements from 2021–2025. Text-only and censored results are retained in the history JSON and are not plotted as numbers.
Open this chart to load the measurements.
Numeric resultEPA-listed exceedance
E. coli
2025 median0
2025 maximum0
Measurements in 202564
0 EPA-listed exceedances in 2025.
View parameter history
Individual numeric measurements from 2021–2025. Text-only and censored results are retained in the history JSON and are not plotted as numbers.
Open this chart to load the measurements.
Numeric resultEPA-listed exceedance
Coliform Bacteria
2025 median0 100ml
2025 maximum0 100ml
Measurements in 202564
0 EPA-listed exceedances in 2025.
View parameter history
Individual numeric measurements from 2021–2025. Text-only and censored results are retained in the history JSON and are not plotted as numbers.
Open this chart to load the measurements.
Numeric resultEPA-listed exceedance
Fluoride
2025 median0.6
2025 maximum0.8
Measurements in 20259
0 EPA-listed exceedances in 2025.
View parameter history
Individual numeric measurements from 2021–2025. Text-only and censored results are retained in the history JSON and are not plotted as numbers.
Open this chart to load the measurements.
Numeric resultEPA-listed exceedance
Iron
2025 median26.5 ug/l
2025 maximum361 ug/l
Measurements in 202564
1 EPA-listed exceedances in 2025.
View parameter history
Individual numeric measurements from 2021–2025. Text-only and censored results are retained in the history JSON and are not plotted as numbers.
Open this chart to load the measurements.
Numeric resultEPA-listed exceedance
Arsenic
2025 median—
2025 maximum—
Measurements in 20259
0 EPA-listed exceedances in 2025.
View parameter history
Individual numeric measurements from 2021–2025. Text-only and censored results are retained in the history JSON and are not plotted as numbers.
Open this chart to load the measurements.
Numeric resultEPA-listed exceedance
Monitoring over time
5-year trends 2021–2025
Available years in the latest 5-calendar-year window. Monitoring volume and descriptive frequency use separate scales.
20251,361 results · 3 listed exceedances
Total results — independent scale
Listed exceedances per 1,000 results — independent scale
This is our descriptive frequency: listed exceedance records divided by result records, multiplied by 1,000. It is not an official EPA compliance rate. Differences in sampling volume and parameters tested affect comparisons. A missing denominator is shown as unavailable.
| Year | Results | Samples | Parameters | Listed exceedances | Per 1,000 results |
|---|---|---|---|---|---|
| 2021 | 986 | 51 | 64 | 1 | 1.014 |
| 2022 | 1,182 | 60 | 64 | 2 | 1.692 |
| 2023 | 1,249 | 57 | 65 | 2 | 1.601 |
| 2024 | 1,257 | 61 | 65 | 0 | 0.000 |
| 2025 | 1,361 | 64 | 69 | 3 | 2.204 |
Year-to-year detail
2025 compared with 2024
Changes describe dataset volumes only. The comparison uses the previous available year.
Results
20241,257
20251,361
Listed exceedances
20240
20253
Samples
202461
202564
Parameters
202465
202569
Parameters with EPA-listed exceedances
Values and limits are reproduced as reported. Different unit/limit pairs are shown separately.
Colour
2 listed exceedance records / 64 tests3.12%
Descriptive frequency of records, not an official compliance measure.
- Highest listed result
- 26 Hazen
- Reported limit
- 20 Hazen
- Records with this unit/limit pair
- 2
- Latest exceedance
- 25 Aug 2025
Iron
1 listed exceedance records / 64 tests1.56%
Descriptive frequency of records, not an official compliance measure.
- Highest listed result
- 361 ug/l
- Reported limit
- 200 ug/l
- Records with this unit/limit pair
- 1
- Latest exceedance
- 25 Aug 2025
Across the year
When were listed exceedances recorded?
Each point represents one listed exceedance record. Records on the same date remain separate.
Colour25 Aug 2025
22 HazenReported result
20 HazenReported limit
LETTERKENNY MIXEDWater supply
3 listed exceedance records across 2 parameters in 2025.
Your mapped supply
Water supply
Every Water Supply Zone used for this page's headline figures is included. Geographic overlaps are reported separately and are not added together or weighted by population.
Letterkenny
51.91% geographic overlap with the Letterkenny Built Up Area.
Technical mapping details
Letterkenny Pollan Dam Mixed Supply
32.00% geographic overlap with the Letterkenny Built Up Area.
Technical mapping details
Letterkenny Mixed
10.09% geographic overlap with the Letterkenny Built Up Area.
Technical mapping details
Detailed data
The complete parameter and listed exceedance tables for the reporting year.
69 parameter rows3 listed exceedance records64 samples
Show detailed data69 parameters · 3 exceedance records
Complete parameter index
All parameters in 2025
| 1,2-dichloroethane | 9 | 0 | 04 Nov 2025 | 3 |
| 2,3,6-trichlorobenzoic acid | 9 | 0 | 04 Nov 2025 | 3 |
| 2,4-D | 9 | 0 | 04 Nov 2025 | 3 |
| Acrylamide | 9 | 0 | 04 Nov 2025 | 3 |
| Aluminium | 64 | 0 | 17 Dec 2025 | 3 |
| Ammonium | 9 | 0 | 04 Nov 2025 | 3 |
| Antimony | 9 | 0 | 04 Nov 2025 | 3 |
| Arsenic | 9 | 0 | 04 Nov 2025 | 3 |
| Atrazine | 9 | 0 | 04 Nov 2025 | 3 |
| Bentazone | 9 | 0 | 04 Nov 2025 | 3 |
| Benzene | 9 | 0 | 04 Nov 2025 | 3 |
| Benzo(a)pyrene | 9 | 0 | 04 Nov 2025 | 3 |
| Bisphenol A | 9 | 0 | 04 Nov 2025 | 3 |
| Boron | 9 | 0 | 04 Nov 2025 | 3 |
| Bromate | 9 | 0 | 04 Nov 2025 | 3 |
| Cadmium | 9 | 0 | 04 Nov 2025 | 3 |
| Chlorfenvinphos | 9 | 0 | 04 Nov 2025 | 3 |
| Chloride | 9 | 0 | 04 Nov 2025 | 3 |
| Chromium | 9 | 0 | 04 Nov 2025 | 3 |
| Clopyralid | 9 | 0 | 04 Nov 2025 | 3 |
| Clostridium Perfringens | 9 | 0 | 04 Nov 2025 | 3 |
| Coliform Bacteria | 64 | 0 | 17 Dec 2025 | 3 |
| Colony Count @ 22°C | 55 | 0 | 17 Dec 2025 | 3 |
| Colour | 64 | 2 | 17 Dec 2025 | 3 |
| Conductivity | 64 | 0 | 17 Dec 2025 | 3 |
| Copper | 9 | 0 | 04 Nov 2025 | 3 |
| Cyanide | 9 | 0 | 04 Nov 2025 | 3 |
| Cypermethrin | 9 | 0 | 04 Nov 2025 | 3 |
| Dichlobenil | 9 | 0 | 04 Nov 2025 | 3 |
| Dichlorprop | 9 | 0 | 04 Nov 2025 | 3 |
| Diflufenican | 9 | 0 | 04 Nov 2025 | 3 |
| Diuron | 9 | 0 | 04 Nov 2025 | 3 |
| E. coli | 64 | 0 | 17 Dec 2025 | 3 |
| Enterococci | 64 | 0 | 17 Dec 2025 | 3 |
| Fluoride | 9 | 0 | 04 Nov 2025 | 3 |
| Free Chlorine | 64 | 0 | 17 Dec 2025 | 3 |
| Glyphosate | 9 | 0 | 04 Nov 2025 | 3 |
| Haloacetic acids (Sum of 5 HAAs) | 9 | 0 | 04 Nov 2025 | 3 |
| Iron | 64 | 1 | 17 Dec 2025 | 3 |
| Isoproturon | 9 | 0 | 04 Nov 2025 | 3 |
| Lead | 9 | 0 | 04 Nov 2025 | 3 |
| Linuron | 9 | 0 | 04 Nov 2025 | 3 |
| Manganese | 9 | 0 | 04 Nov 2025 | 3 |
| MCPA | 9 | 0 | 04 Nov 2025 | 3 |
| Mecoprop | 9 | 0 | 04 Nov 2025 | 3 |
| Mercury | 9 | 0 | 04 Nov 2025 | 3 |
| Metaldehyde | 9 | 0 | 04 Nov 2025 | 3 |
| Microcystin-LR | 6 | 0 | 04 Nov 2025 | 3 |
| Nickel | 9 | 0 | 04 Nov 2025 | 3 |
| Nitrate | 9 | 0 | 04 Nov 2025 | 3 |
| Nitrite (at tap) | 9 | 0 | 04 Nov 2025 | 3 |
| Odour | 55 | 0 | 17 Dec 2025 | 3 |
| PAH | 9 | 0 | 04 Nov 2025 | 3 |
| Pendimethalin | 9 | 0 | 04 Nov 2025 | 3 |
| Pesticides - Total | 9 | 0 | 04 Nov 2025 | 3 |
| pH | 64 | 0 | 17 Dec 2025 | 3 |
| Propyzamide | 9 | 0 | 04 Nov 2025 | 3 |
| Selenium | 9 | 0 | 04 Nov 2025 | 3 |
| Simazine | 9 | 0 | 04 Nov 2025 | 3 |
| Sodium | 9 | 0 | 04 Nov 2025 | 3 |
| Sulphate | 9 | 0 | 04 Nov 2025 | 3 |
| Sum of PFAS (sum of 20) | 9 | 0 | 04 Nov 2025 | 3 |
| Taste | 55 | 0 | 17 Dec 2025 | 3 |
| Tetrachloroethene & Trichloroethene | 9 | 0 | 04 Nov 2025 | 3 |
| Total Chlorine | 64 | 0 | 17 Dec 2025 | 3 |
| Total Organic Carbon | 9 | 0 | 04 Nov 2025 | 3 |
| Triclopyr | 9 | 0 | 04 Nov 2025 | 3 |
| Trihalomethanes(Total) | 9 | 0 | 04 Nov 2025 | 3 |
| Turbidity (at tap) | 64 | 0 | 17 Dec 2025 | 3 |
Showing 69 of 69 parameters.
EPA exceedance dataset
Listed exceedances in 2025
Newest first. Sample IDs distinguish records that may otherwise look identical.
Common questions
Frequently asked questions
Is Letterkenny tap water safe to drink?
WaterCheck Ireland does not issue a current safe or unsafe verdict. This page presents historical monitoring data. Check Uisce Éireann for any current Boil Water or Do Not Consume notices affecting your address.
Can you drink tap water in Letterkenny?
WaterCheck Ireland provides historical drinking-water monitoring data, not a current safe or unsafe verdict. For current Boil Water or Do Not Consume notices, check your Eircode with Uisce Éireann.
What is the tap water quality in Letterkenny?
In 2025, monitoring data for 3 Water Supply Zones mapped to Letterkenny included 1,361 results across 69 parameters. The separate EPA-listed exceedance dataset contains 3 records for those zones in 2025. These figures summarise historical records and are not a current safety verdict.
Who monitors drinking water quality in Letterkenny?
The historical monitoring figures shown here come from drinking-water datasets published by the Environmental Protection Agency (EPA), Ireland. Uisce Éireann operates public water supplies and publishes current supply notices.
What is a Water Supply Zone?
A Water Supply Zone is a defined area supplied by a public drinking-water system. Monitoring records apply to the zone as a whole, so sampling locations can be outside the Census Built Up Area.
What does a listed exceedance mean?
It is a record published in the separate EPA exceedance dataset. WaterCheck Ireland reproduces those records and does not infer additional exceedances or turn the record count into a safety assessment.
How can I check current water notices for my Eircode?
Use your Eircode on the Uisce Éireann website to check current Boil Water and Do Not Consume notices. This page is based on historical monitoring data and is not a live notice service.
Explore nearby reports
Water Quality Near Letterkenny
Nearest published Built Up Areas, ordered by straight-line distance between Census reference points.
How this page is made
Sources and methodology
- Settlement
- Census 2022 Built Up Area: Letterkenny. Population refers to the whole Built Up Area.
- Supply mapping
- Uisce Éireann Water Supply Zone boundaries are matched geographically to the settlement.
- Monitoring
- EPA monitoring results and the separate listed exceedance dataset, 2021–2025.
- Interpretation
- Geographic overlap measures land area, not population served; monitoring applies across the full supply zone.
Additional spatial intersections (1)
Retained for mapping transparency; excluded from primary monitoring totals.
| Zone | EDEN | Class | Geographic overlap |
|---|---|---|---|
| Pollan Dam | 0600PUB1020 | BOUNDARY_TOUCH | 0.045568% |