Irish Water is appealing to people to conserve water when they can following a significant upsurge in usage since the imposition of Covid-19 restrictions.
It said treatment plants are already working to their maximum capacity.
Irish Water said domestic metering data shows that households are using an additional 24 litres of water per person per day, a 20% increase from February.
The utility said that two thirds of supply goes to domestic sources so that the closure of many businesses because of coronavirus has only partially off-set the rise in demand.
It is appealing to consumers to take simple measures to conserve supply such as stopping the use of powerwashers at home; using a watering can rather than a hose in the garden; taking showers over baths and fixing any dripping taps.
The company said that when Covid-19 restrictions are lifted, many commercial premises will need to use extra water to clean and flush their plumbing systems or to complete deep cleans, and that water usage in homes will continue to remain higher than normal.
Irish Water's Managing Director Niall Gleeson said: "It is really important that everyone follows the HSE guidance on handwashing, however there are some ways to conserve water that will not impact on hygiene.
"Insights from meter reads show that households are now using 20% more water and we can see a significant change in water usage patterns in commuter belt towns and rural areas where significant numbers of people would usually be out of the house for long periods during the day.
"We are also conscious that we have had an extremely dry spell so we are continually monitoring our water sources for any signs of drought," he added.