Irish Water has revealed it expects a range of problems with its first bills when they are sent out from next month.

The company says details such as the number of people in a house may be incorrect, more than 2,000 meters will not be read because of technical issues, and up to 150,000 properties with a private well and septic tank will be mistakenly billed.

The company said they anticipated "a lot" of calls, and 750 staff will be in place in call centres to handle the queries.

"This is the first time we're going to be sending domestic water bills - we're going to send almost 1.7 million bills" she said.

"It's not unusual that there would be teething problems when you do something like this on this scale for the firs time".

"So we're putting additional resources into our contact centre, so that we can work with customers to resolve any of the information deficits and gaps and errors that we may have."

Meanwhile, the Government announced a new deadline for registering for water charges last night.

Environment minister Alan Kelly said households will have to register before June 30. If they do not, they will not qualify for the €100 water conservation grant.

Minister Kelly told TDs that more details about the grant, and how it would be paid, would be announced next month.

"The Department of Social Protection will be communicating separately with households from July onwards (on that issue)," he said.