"The Hastings and Havelock North supplies have inherent levels of calcium (moderate hardness) that forms lime scale deposit in kettles and pipes. These deposits would often mask or temporarily seal pinhole leaks."
He said copper connection failures started to be noticed just before the gastro outbreak in August last year, but the introduction of chlorine to the system had highlighted the issue.
A programme of connection replacements over the next 10 years had begun before the contamination event, but given the issues it was likely that this would need to be completed sooner than planned, he added.
Devine Plumbing's Cam Devine said there had been a notable increase in problems with hot water cylinders since the chlorine was introduced to the network.
"We've had 30 per cent more calls for hot water cylinders in Hastings since it happened with valves corroding and falling apart.
"We also know a lot of people are unhappy - especially in Havelock North, you go to their house and they say the kids don't want a bath because it's like bathing in a swimming pool."
The issue of calcification of the copper pipes was also a problem for the Hastings area, where it was seen significantly more than in the Napier region, he said.
"We service backflow prevention valves and in Hastings the washers are calcified, green and falling apart and the copper is wearing thin."
He said when people had leaks under their floors in particular it could prove expensive with the whole house sometimes needing to be re-plumbed.