Irish Water and Wexford County Council have issued a boil water notice after the detection of giardia in the water supply.
The notice applies to all customers on the Wexford Town public water supply. Anyone affected by the notice should boil their water before drinking it.
Giardia is a parasite that can cause stomach cramps, bloating, nausea and diarrhea.
Customers are advised to contact their GP for medical advice if they feel unwell.
Wexford Town and its environs were earlier alerted to low pressure, pressure fluctuations and a possible loss of supply, which has been extended until 9 o'clock tomorrow morning.
Separately, Wexford County Council said it had received reports of trees down and localised flooding throughout the county following bad weather today.
It said the L4038 Garryrichard to Folksmills is closed until tomorrow due to a number of fallen trees, with council crews on site.