According to the latest figures from the environmental watchdog, some 442 cases of contaminated public drinking water supplies were flagged up in the period between March 2007 and December 2008.
These included a number of instances where households were forced to boil their water or seek alternative supplies due to the presence of potentially-fatal bugs such as E Coli.
Furthermore, figures released by the EPA to the Irish Independent also show that the watchdog undertook 253 investigations into how well local authorities across the country dealt with complains from the public regarding water quality.
In total, 26 directives were issued by the body over the period.
These latest figures come soon after the EPA reported that traces of E Coli had been found in around eight per cent of Irish drinking water supplies, though the agency has stressed that water quality levels continue to improve.