Plans for Irish Water to charge 58,000 households with excessive water usage were delayed amid concerns over data protection and how to deal with customers without water meters.
Letters and information were prepared last October telling households what they could do to cut water consumption and how Irish Water could help.
Internal records obtained via FOI describe discussions to ensure plans to start charging would be "very carefully managed". They explain how there would need to be messaging around how Irish Water was going to manage households that had no meters and how excessive use would be calculated.
However, the plan was postponed to deal with issues around how customer data would be managed, unmetered houses, and building IT infrastructure to support the project.
Talks are now underway with the Data Protection Commissioner over how to manage the volume of personal data.
This would include names, addresses, water usage, the number of people living in each house, and special medical requirements of residents who might need more water.
It also includes strong indicators of when people are likely to be home, based on when water is being used in the day, which in the event of a breach could create a burglary risk.
An Irish Water official said that household water conservation was a "unique project" and that the Department of Housing were consulting with the Data Protection Commissioner.
She said: "[We have] taken all the necessary steps to try to ensure that our approach is in line with GDPR requirements and that all measures are taken to protect personal data."
The official said that while GDPR was a key issue, customer communications, building IT systems and the approach to identifying unmetered households were also "essential to the progression of the project."
"All of these elements are reaching a state of readiness. The project cannot proceed unless and until all elements are ready," she said.
The internal Irish Water records explain how the process for charging would happen with a "call to action" letter and leaflet sent to households at first.
This would include a "step-by-step guide, what options are open to them, what help can Irish Water provide, what can the household do?"
A second letter would be issued in April and a third reminder sent in January 2021 with the first bills issuing in July 2021 if excessive use had not been curtailed.
The excess would be charged at €1.85 per 1,000 litres up to €250 per service.
Customers with water in and water out services will be capped at €500 a year.