The Government is being urged to publish ESRI research on water affordability, commissioned by the Department of the Environment.
The Society of St Vincent de Paul has written to Minister Phil Hogan, asking him to release the information.
The Society says water affordability must be made a key principle for the provision of water in Ireland, but some people cannot afford some of the possible charges.
St Vincent de Paul is suggesting a sliding scale based on income, to ensure sufficient water for vulnerable households.