1,400 premises affected by Clontarf water warning
Dublin City Council said it is still trying to find the cause but has ruled out E coli.
Residential and commercial properties are affected from the Howth Road to Castle Avenue and from the Howth Road at Collins Avenue to Clontarf Road.
City council crews are currently providing an alternative supply of water to those areas and will continue to do so for as long as the problem persists.
People living and working there were told on Sunday night not to drink their tap water, after what the council described as irregularities were detected in the supply.
Residents have also been told not to use the water for cooking, even if boiled, because the water is not rendered safe by doing so.
Bathing water and water used for flushing toilets is not included in the alert.
Dublin City Council says it has not at this stage confirmed a bacteria outbreak and is still trying to find out the exact cause.
However, it has ruled out the presence of metals such as lead in any of the samples.
Further test results are due out later this afternoon.