Re-piping a House: How to Tell When Repairs Have Stopped Being the Answer

There is a particular phone call we have learned to recognise. It is the third one from the same address, and it starts the same way every time: another one has gone.

Nobody plans to re-pipe a house. It is not a thing people want, or budget for, or enjoy looking at afterwards, because when it is done well you cannot see it at all. What happens instead is that a house starts leaking, and then keeps leaking, and somewhere in that sequence the owner has to decide whether to keep paying for repairs or to deal with the cause.

This is about how to make that call. Not with a rule of thumb, but with what the house is actually telling you.

How do I know it’s the pipes and not just bad luck?

Bad luck looks like one leak. A pipe failing because of the pipe looks like a pattern, and the pattern has three features: the leaks are in different places, they come close together, and every one of them is in the same material.

Three houses from our own job records, which we keep coming back to because they are the clearest examples we have.

A rental in Randwick Park: we were there on 8 April for a burst under the house and a garden tap that would not shut off. Four weeks later, on 5 May, two more burst points under the subfloor — one on the hot line, one on the cold. Twelve days after that, on a Saturday, the hot water pipe under the house again. Three call-outs in six weeks, three different sections of pipe, none of them anywhere near the last one.

A house in Highland Park, over thirteen months: a split fitting under the kitchen sink and two leaks in the subfloor; then the pipe feeding the kitchen tap, and while we were testing that repair a second section let go in front of us; then the laundry, where we had to cut open the wall beneath the tub; then roughly a metre of pipe under the floor.

A property in Mairangi Bay: the garage ceiling in January, a completely different section the following May — plus a fitting we could see was loosening, so we replaced that too before it went — and then a pinhole leak in the subfloor the year after.

None of those houses had bad luck. All three were plumbed in Dux Quest.

Why does fixing one leak seem to bring on the next one?

This is the question we get asked most, usually with an edge to it, and the honest answer is worth spelling out.

Repairing a pipe does not cause the next failure. What it does is remove the section that was going to fail first — and in a house where the whole system is the same age and the same material, there is always a next-weakest point waiting behind it. Water pressure does not politely stop at the repair. It goes looking for whatever is now the thinnest, most degraded piece of pipe in the building.

The Highland Park job is the plainest version of this we have on record: we replaced the burst section, turned the water back on to test it, and another length of the same pipe split while we were standing there. That is not a repair going wrong. That is a system telling you, in the clearest way it can, that the problem was never the piece we just cut out.

Once that has happened once or twice, you are no longer buying repairs. You are buying time, in increasingly short instalments, and paying a call-out for each one.

Can’t you just replace the pipe under the house and leave the walls alone?

You can. We usually advise against it, and the reason is not the one people expect.

If you replace only the accessible pipe — the subfloor runs, the length in the garage ceiling, whatever you can reach without cutting anything — you have not reduced the amount of old pipe that is going to fail. You have just removed the parts that would have failed where you could see them. Everything that is left is inside a wall, above a ceiling, or under the floor of a room. The next burst is now guaranteed to be in the expensive location.

We wrote exactly that to the owner of the Mairangi Bay property after the garage ceiling repair, before the second and third failures, and we would write it again. A leak in an exposed subfloor run is a morning’s work. The same leak inside a bathroom wall is a plumber, a builder, a painter, and a bathroom you cannot use.

Partial re-pipes do make sense in one situation, and only one: when the part you are replacing is the part that is already open. More on that below.

What does a full re-pipe actually involve?

Here is a real one, in One Tree Hill. Hot and cold water pipework replaced to every fixture in the house: two toilets, two hand basins, two showers, a bath, a laundry tub, the washing machine, and the hot water cylinder. Pipe under the subfloor and pipe concealed inside the walls, both.

A wall opened up behind an upstairs vanity during a house re-pipe, with old black pipe and the new pipework in the cavity, and the location written on the wall in marker

That photograph is what a re-pipe looks like from inside the house. To reach the pipe feeding a fixture, we cut the gib behind it — a hole per fixture, and in places a strip of ceiling. We write on the wall what each opening is, because by the third day there are a lot of them and nobody wants to guess.

A ceiling opened along its length with new water pipe running through the joists

Three things people are usually surprised by:

The new pipe is not copper. Modern re-pipes are done in PEX, which is a stable, pressure-rated plastic and has none of the failure history of the 1970s polybutylene it replaces. Copper still gets used where it has to be, but it is no longer the default.
We do not patch and paint. Making good the gib and the decorating is a separate trade, and we scope it that way so nobody is surprised by it. At the One Tree Hill house the owner arranged their own plasterer and painter after we finished. If you would rather it all came from one place, that is a builder-led job with us inside it.
The water is not off for days. A re-pipe is staged. Water goes off while we cut over a section and back on before we leave, so the house is liveable in the evenings even while it is a building site during the day.

When is the cheapest time to do it?

During a renovation — and this is not us being coy about the price. It is arithmetic.

In a bathroom or kitchen renovation, the walls are already open, the fixtures are already off, and the gib work and painting are already in the builder’s scope. Replacing the pipework at that moment costs the plumbing and almost nothing else. Doing the identical work in a finished house means paying separately for every one of those things, and living with the mess.

A house in Forrest Hill is the small version of this done right. The owner was replacing a tired shower — new tray, new enclosure, new rail and mixer. With the wall open we replaced the Dux Quest pipework running behind the shower and the vanity, and the damaged plywood under the old tray while we were there. That is a partial re-pipe, and it was the right call, because the part we replaced was the part that was open anyway.

The trap is waiting for a renovation that keeps not happening. If the chain of failures has already started, the repairs and the water damage between now and that renovation can quietly cost more than the re-pipe would have. That is a judgement call, and it is yours — but make it deliberately, with the repair history in front of you, rather than one call-out at a time.

What can I do if I’m not ready to re-pipe yet?

Four things, in the order they are worth doing.

Get the pressure down. Auckland mains pressure typically runs somewhere between 500 and 900 kPa. Bringing the house down to around 400 kPa with a pressure limiting valve meaningfully reduces how often aged pipe lets go. It is not a cure and we will not pretend it is — but on a house that is going to be re-piped in two years rather than two months, it buys real time. We recommended exactly this on a West Harbour rental after a Dux Quest burst under the floor, as the alternative to doing the whole job that week.

Make sure you can turn the water off. At the Highland Park house we could not investigate the subfloor leak on the first visit, because the mains isolating valve at the property was faulty and would not let us restore water afterwards. We had to report it to Watercare, wait for their repair, and come back two days later. Find your water meter box now, and check the valve turns, while nothing is wrong.

Read the meter once a month. The one-minute meter check catches a leak that is running under the house before it catches your water bill or your floor.

Do not close things up. In a Forrest Hill basement we found a bulkhead that had been screwed shut, with gib inside it already water-stained — someone had been at that leak before and covered it over. The next person to open it was us, after the tenant heard dripping and could not find the source. Panels that come off easily are worth more than panels that look tidy.

Does insurance pay for a re-pipe?

No, and it is worth understanding why so you are not counting on it.

House insurance covers sudden and accidental damage. When a pipe bursts, the policy is generally looking at what the water wrecked — flooring, gib, ceilings, contents — and often at the cost of getting to the burst. What it does not do is pay to replace pipework because that pipework is at the end of its service life. That is maintenance, and maintenance is the owner’s.

There is a sharper edge to this on a house with a known history. Once you have been advised in writing that the system is failing, a leak that has been seeping for months becomes considerably harder to argue as sudden. That cuts both ways for owners and property managers: the plumber’s report that supports a claim is the same document that shows you were told. Fix things when you are told about them, and keep the paperwork.

If a claim is in front of you now, what insurers actually look at is the place to start.

Is it always Dux Quest?

Nearly always, in the houses we get called to — but not quite always.

Dux Quest is the 1970s and 80s polybutylene, grey or black, and it is the pipe behind almost every chain-of-failures job in this article. What it is, and why it fails.
Galvanised steel, common before the 1960s, does not usually burst. It corrodes from the inside and closes up, so it shows itself as falling flow and rusty water rather than water on the floor — which is why it often gets mistaken for a water pressure problem.
Copper from the 1960s onward is generally still doing its job, and pinhole failures in copper are individual faults rather than a sign the whole house is due.

The distinction matters, because only the first of those makes an entire-house replacement the obvious answer.

Common questions

How do I tell what pipe I have?

Look under the house or under a vanity with a torch. Grey or black flexible plastic of that era is very likely Dux Quest; dull grey metal is galvanised; copper is unmistakable. If it is a mixture — and in a house that has been repaired a few times it usually is — the oldest material present is the one that sets your timeline.

Can it be done one room at a time?

Yes, and sometimes that is the only way it fits a budget. Plan it as one job in stages rather than as a series of unrelated repairs, so the joins between new and old are in places we chose, and so the sequence follows the renovation rather than the leaks.

How long does a whole house take?

For a standard three-bedroom house with one or two bathrooms, think in days rather than weeks for the plumbing itself. The making good afterwards is usually the longer half.

It’s a rental. Who pays, and what about the tenant?

Pipework is the owner’s, not the tenant’s. The practical issue is that a house with a failing system will produce after-hours call-outs with a tenant in it, sometimes on a weekend with the water shut off at the main — which is how the Randwick Park Saturday job happened. If you manage properties, the repair history is the argument to take to the owner. Our guide for property managers covers how to frame it.

Will re-piping fix my water pressure?

Sometimes. If the flow has dropped because galvanised pipe has silted up internally, yes, noticeably. If the pipe is Dux Quest, pressure is usually not the complaint — bursting is.

One pipe has just burst and I’m reading this with the water off.

Then start here instead: what to do in the first ten minutes. Come back to this page afterwards.

Been out to the same house more than once this year? Send us the repair history and we will tell you honestly whether you are near the point where replacing the pipework is the cheaper option. Call Nexus Plumbing or email [email protected].