Irish Water meter installers have submitted a raft of claims for extra money from the utility.

It comes amid claims they incurred higher than expected costs when installing thousands of meters, RTÉ's This Week has learned.

It is understood that a number of the utility's regional contractors have claimed they encountered thousands of wrongly-sized junction boxes; water pipes which were too close to the surface or other significant differences between the initial scope for the job and the actual ground conditions.

The issue arose most frequently in urban estates where the housing stock was built during boom-time construction.

Contractors believe that most of the problems can be traced back to below-par building work carried out by private builders and insufficient post-construction inspections by the relevant local authorities.

In the most extreme example, Irish Water meter installers would have expected to simply insert meters into existing junction boxes, but would have discovered when they arrived at certain estates that they needed to excavate and re-mediate below-par pipes and connections.

A number of the utility's regional meter installers are now claiming that Irish Water is liable for some or all of the extra costs which have been incurred, specifically on this extra cost over-run.

Irish Water and the private companies have begun to engage with official mediators on the issue as part of a confidential resolution mechanism, which is governed by Institute of Engineering Ireland (IEI) mediation rules, sources close to the process told RTÉ News.

However, it is understood that Irish Water has claimed that any such costs should be borne by the contractors as part of the risk which they assumed as part of the contract.

Irish Water has also maintained that the extra costs should have been factored into the contingency which was part of the contract award.

Well-placed sources told RTÉ News that Irish Water's contracts are regarded within the industry as being strongly-worded to protect the company against any claims for cost-over runs.

The contracts are based largely on similar bespoke contracts used by Bord Gáis Éireann, now named Ervia, in the gas business.

Sources close to the process declined to be drawn on the value of the cost-claims submitted to Irish Water.

Irish Water has previously said that the over-all cost of the water metering programme will be €539 million.

The cost claims in this case are specific to the actual problem which the installers encountered, which means that they could still deliver their overall contractual commitments on or below budget if they achieved efficiencies in other areas of the meter installation process.

None of the contractors would comment on the claims when contacted last week.

Irish Water declined to confirm that any claims had been made or to comment on any detail relating to the claims.

"If any claims arose from contractors, we would not confirm them publicly or comment on them for reasons of commercial sensitivity," a spokesperson for the utility told RTÉ News.

The mediation process is time-limited but it can also be suspended if progress was slow.

If mediation proved to be unsuccessful, the next stage would be legal action via the courts, according to sources close to the dispute-resolution process.