1,700 small private supplies are registered with local authorities, but the Environmental Protection Agency says many more are not included in official records.
The environmental watchdog says new laws are needed to make sure all private drinking water supplies are properly registered.
The EPA says many private wells are not registered - despite supplying water to schools, nursing homes and sports clubs.
The fact they they are not registered means they can't be monitored.
1,700 small private supplies are registered with local authorities, but the Environmental Protection Agency says many more are not included in official records.
Noel Byrne, from the EPA's Drinking Water and Waste Water Enforcement team, says current laws need to be updated.

New Appeals System For Asylum Seekers Comes Into Effect
Bord Bia Review Published In Light Of Controversy Surrounding Brazilian Beef Importation
KCC Report Reveals North Vs South Divide In Kildare
Kildare TD Highlights Difficulties Faced By Wheelchair Users In Curragh School
"A Fall Every Week" : Mayor Of Naas Calls For Alterations To Kilcullen Road
Local TD Accepts Data Centres Are A "Particular Issue" In Ireland
Kildare Dog Shortlisted For Bravest Pet Award
Kildare Senior Football Team vs Kerry