Wairarapa plumbers are warning that for many people in the region it is not a case of if their water pipes will burst but when.
Many houses in the region built in the late 1970s or 1980s feature a black polybutylene water piping system called Dux Qest.
The product was discontinued after hundreds of faults were reported throughout the country, but for many that move came too late.
Mark Forsyth of Plumbing and Heating Solutions said the dodgy piping was in "a lot of houses" throughout Wairarapa, and that sooner or later the pipes always leaked.
"It would be fair to say that if you've got black Qest pipes in your house they will [fail] but it's just a matter of when."
He said the pipes themselves cracked and gave way or else the acetyl fittings cracked, spraying water over whatever was near.
The pipes could be in walls, ceiling or underfloor, with the ceiling piping liable to make a "bigger mess" when it leaked.
A plumber for nearly 30 years he said often people chose to repair the leaks to keep the cost down but that only kept the problem at bay until another area of the piping leaked.
He said replacing the piping could be done for $4000-$8000 depending on the the size of the house and the ease of access to the pipes.
But despite the cost full replacement was preferable to simply fixing the leaks as insurers would often not cover the damage after the owner had been made aware of the initial problem.
However he said having the Dux pipes was not the be all and end all.
"It's not a reason not to buy a house, but you need to take that cost into account."
He stressed the product was quickly scrapped once the problem was known and houses built from the 1990s onwards were fine.
Masterton Plumbing Services owner David Leigh said initially many of the problems in the 1970s were down to poor installation or workmanship.
But the quality of the product was soon found to be wanting with the lifespan of the pipes using cold water about 10-15 years.
Similar modern products could be expected to last 25-50 years, he said.
Carterton District Council building inspector Bruce Livingstone said it was not an issue for the council.
"We can't tell people to take them out - it's owner beware."
But he said he was aware of the problem and the pipes had been "quite prevalent" in the past.
"Most of them if they haven't failed and if they're still around then they will be about to fail."