Irish Water says lead problems in the water system have been ongoing for years, but were dealt with at local level until now.

Homeowners in Dublin have become the first to receive letters from the utility, warning them that their supply may be contaminated with unsafe levels of lead.

Around 26,000 homes around the country will be sent similar letters in the coming weeks.

Jerry Grant is head of asset management at Irish Water.

He says the issue of lead in the water is not new, but they have just collated the information on a national level for the first time.

"If you go back over EPA reports over the last 15 years, you'll see indications in those reports of lead problems from place to place - the difficulty was that individual local authorities, there were 34 of them, were dealing with this on an ad-hoc basis", he told Newstalk Breakfast.

"So from time to time, lead exceedances would arise and they'd be dealt with locally between the local authority and the HSE".

"Obviously when we took over responsibility from January 2014, we began to collate all that information and...pick up more detail around the extent of lead piping in the system" he added.