Dux Qest — leaky pipes?

60 years ago all New Zealand houses used galvanised steel pipes for the water supply and distribution.

Water and steel don’t mix well, due to rusting. The flow of water containing impurities is abrasive and the chemicals in water attack the inside galvanising of the pipe.

Over time, although the exterior of the pipe looks okay, the inside of a pipe can start to corrode. The corrosion restricts water flow, and eventually blocks the flow completely.

So by the 1960s most plumbers moved to using copper. Copper does not corrode in the same way, it is very stable in most domestic situations. But copper used in the piping became expensive.

In the 1970s plastics were experimented with. One new material was polybutylene. One manufacturer, Dux, came up with a product known as Dux Qest. (That is the correct spelling by the way. It is not spelt Quest.)

Dux Qest was extensively used in New Zealand in a period from 1977, when importing began, until 1987 when it ceased. It was used in both for new houses and for replacing old galvanised pipes in existing houses, or renovations. Many houses in Nelson, built or modified from 1979 to some time after 1987 when the existing stocks were sold, have potentially leaky water pipes.

Dux Qest has proved to be severely faulty.

With this early formulation of polybutylene, Dux Qest, the chlorine in the town water supply reacts with the plastic, causing it to erode, and/or become brittle. Eventually the plastic breaks down at the stress points, either the bends or where the pipes are cramped when they join together and they can begin to leak. Sometimes it can be a pinhole leak, just exerting a fine spray, or it can be more substantial. When those pipes split they can be like a tap, full blast, except inside your walls.

Leaky pipes can cause a lot of damage. Hundreds of litres of water can be discharged inside the house before you notice and the boundary water tap is turned off.

Then the Dux Qest pipes need to be replaced. That generally means removing the wall linings to two walls in a bathroom, and as required in the kitchen. Access to some pipes can be difficult, particularly in two storey houses.

If you replace some of the wall linings, it can become all of them. You might choose to replace the ageing fittings too.

Therefore replacing a leaking pipe can lead to a full bathroom renovation, which can end up costing tens of thousands of dollars. This cost may not be covered by your house insurance policy, particularly if it is a known problem.

So, leaking pipes are expensive to remedy. It can become very expensive.

It’s better to know about this issue before you buy a house and factor any costs into your purchase price.

← Home insulation history and materials. 2023 changes Smoke alarms? Ionising or photoelectric? →