No, it is generally not recommended to drink the tap water from the toilets on Irish trains (Iarnród Éireann). The water in the onboard tanks is meant for handwashing and flushing only; it is not filtered to potable (drinking) standards and could contain bacteria. While modern Irish trains are very comfortable, they do not have public water fountains on board. Instead, passengers are encouraged to bring their own reusable bottles and fill them at the Ecofill water units now located at major stations like Dublin Heuston, Connolly, and Galway. These station units provide free, triple-filtered, and UV-treated chilled water. If you find yourself thirsty during the journey without a bottle, your best option is to purchase bottled water or beverages from the onboard catering trolley, which services most InterCity routes, though many travelers prefer the eco-friendly and cost-effective station refill stations.