It will take a minimum of a week to lift a boil water on the Longford Central Supply.
According to Irish Water over 17,000 customers in County Longford are affected by the possible presence of cryptosporidium in the supply.
The issue arose following a deterioration in the raw water quality of Lough Forbes treatment plant.
It's hoped a change in weather conditions over the coming week will help rectify the problem.
Speaking on Let's Talk John Gavin Operations Lead with Irish Water said the churning effect in the water should settle in the coming days.