Broken and burst pipes: why they fail, and what to do the moment one does

01 Supply and drainage: two systems, two kinds of trouble

Your home runs two entirely separate pipe networks, and telling them apart is the first move in almost every pipe problem.

The supply system is the pressurised half. Water arrives from the street main, through your water meter at the boundary, and every pipe past that point is under mains pressure day and night, whether a tap is open or not. That is why a supply leak sprays, never stops, and shows up on the meter even at three in the morning.

The drainage system is the other half, and it carries no pressure at all. Wastewater leaves each fixture and falls to the sewer by gravity, which means a drainage pipe only holds water while a fixture is actually running. A leak there shows up intermittently, after a shower or a wash, and never on a still meter.

Find your main stop tap now, before you ever need it in a hurry, and make sure it turns. An old stop tap that has not been moved in years can seize; a plumber can free or replace it in a routine visit, which is a far better time to discover the problem than during a burst.

02 Why pipes fail

A broken pipe is almost always one of a short list of mechanisms. Knowing which one you are dealing with tells you whether it is a one-off or a warning about the whole run.

Age and wear. Every pipe material has a working life, and the joints and fittings age fastest of all. A house full of original galvanised steel or early plastic is not failing because of one bad day; it is failing because the material has reached the end of its service life, and the next weak joint is only ever a matter of time.

Corrosion. Metal pipe thins from the inside out. It can go uniformly (the whole wall wears down), or as pitting (a tiny pinhole eats through in one spot, the classic copper failure), or galvanically where two different metals meet in water and behave like a small battery, sacrificing the weaker one. Section 05 covers what corrodes and what does not.

Water pressure that is too high. Utilities often set mains pressure high to reach every home on the network, and that baseline can sit above what household plumbing is meant to carry. High pressure stresses every joint continuously, accelerates corrosion, and shortens the life of taps, hoses and appliance valves. A pressure limiting valve at the meter brings it back into range, and if your taps thump or your flexi hoses keep failing, pressure is the first thing to have measured.

Water hammer. Moving water has real mass. When a quick-closing valve (a washing machine, a dishwasher, a quarter-turn tap) stops it dead, the pressure wave has nowhere to go and slams through the pipework. You hear it as a bang; the pipes feel it as a shock that works on joints and hoses every single cycle. It is on the symptom desk below because it is so often the thing people learn to live with, right up until a joint gives out.

Ground movement. Much of Australia is built on reactive clay soils that swell when wet and shrink when dry. That movement flexes a slab and shears rigid buried pipe at its joints, which is why a drainage line can crack years after it was laid perfectly. A leak that keeps returning at the same buried joint is usually the ground, not the pipe.

Temperature. Pipes expand when hot water runs through them and contract as they cool, and years of that cycling work joints loose (thermal fatigue). In frost country a single freeze can split a pipe outright. Both are section 06.

03 A burst pipe: the first five minutes

A burst is a supply pipe, under pressure, letting go, and the volume of water it moves is the whole problem. The damage in the first five minutes is almost entirely in your hands, and the order matters.

1. Shut the water off at the main stop tap. This is the one from Fig. 2: at the meter, clockwise to close. If you have an internal isolation valve and it is closer, use whichever you reach first. Everything else is easier once the water has stopped arriving.
2. Kill the power to anything wet. If water is anywhere near light fittings, power points or an appliance, switch off that circuit (or the mains) at the switchboard before you touch anything. Water and electricity is the part of a burst that hurts people, not property.
3. Open the lowest cold taps. With the main off, run the lowest taps in the house to drain the pipes down. It relieves the trapped pressure and empties the line, so there is less water left to escape from the break.
4. Contain and lift. Move what matters above the water, lift rugs, and get buckets and towels under the leak. Ceilings holding water are dangerous; if a ceiling is bulging, keep people out from under it.
5. Photograph everything before you clean up. The water, the source, the damage to floors, walls and belongings. Insurers pay on evidence, and the evidence disappears the moment you start mopping.
6. Call a licensed plumber. The water is off and the house is safe; now it is a repair, not an emergency. If you rent, tell your landlord or agent at the same time, in writing, and let them arrange the plumber unless it cannot wait.

04 Finding a leak you cannot see

Not every leak announces itself with a spray. The expensive ones are slow, concealed in a wall, a ceiling or under a slab, and they can run for months. The good news is that the pressurised supply system gives you a way to catch them without opening anything: the meter test.

The meter test only catches supply leaks, because only the supply side holds pressure with the taps off. A drainage leak that only weeps when a fixture runs will not move the meter, and that difference is itself diagnostic: a leak that shows on a still meter is a pressurised pipe; a leak that only appears after you use water is a drain.

The other signs of a concealed leak are worth reading in the same way:

• A damp patch or stain is rarely directly under the fault. Water tracks along framing and slab and surfaces at the low point, which is why the plumber traces rather than guesses.
• The sound of running water with every tap off is a pressurised supply leak announcing itself.
• A warm patch on a floor points at a hot-water supply line leaking under the slab.
• A musty smell or mould in one spot, an unexplained jump in the water bill, or a gradual drop in pressure all belong on the list.

A hidden leak is not a wait-and-see problem. Even a slow one wastes a surprising volume of treated, drinking-quality water over a year (YourHome, the Australian Government's guide to sustainable homes), and the structural damage compounds quietly the whole time. Finding a concealed leak precisely, without opening every wall, is exactly what a licensed plumber's acoustic listening gear, thermal camera and moisture meters exist for.

05 What pipes are made of, and how they corrode

What your pipes are made of decides how they age, whether a failure is a patch or a re-pipe, and how green the replacement can be. These are the materials you will meet in an Australian home, roughly oldest to newest.

Corrosion is not one thing. Uniform corrosion thins a whole pipe evenly. Pitting concentrates the attack into a spot and drills a pinhole, which is how sound-looking copper springs a leak. Galvanic corrosion happens wherever two dissimilar metals are joined in water (an old galvanised line plumbed into newer copper is the classic culprit): the pair acts like a battery and the less noble metal corrodes fast. High water velocity and pressure add erosion-corrosion, scouring away the protective film a pipe would otherwise grow. This is why the honest answer to a failing galvanised run is usually to replace it, not to chase pinholes one at a time.

The eco angle sits here too. Copper, stainless steel, cast iron and HDPE are all recyclable, and choosing a durable, recyclable material that will not need replacing in a decade is the greenest plumbing decision most homes ever make. PVC is cheap and long lasting but is neither biodegradable nor easy to recycle, which is why modern sustainable builds increasingly reach for PEX, HDPE and recycled copper instead.

06 Frost and heat: the temperature failures

Frozen pipes are a real cause of bursts, but honesty matters here: for most of coastal Australia they are not a concern at all. Where they bite is the cold country, the alpine areas, tablelands and highlands where hard frosts are normal: the Snowy Mountains, the ACT, the Central and Southern Tablelands, New England, the Victorian high country and Tasmania's highlands. If that is not where you live, you can read this section as background and move on.

Where it does freeze, the mechanism is simple and unforgiving. Water expands by roughly nine per cent as it turns to ice, and an ice plug in a pipe builds enormous pressure in the closed length of water between the plug and a shut tap until the pipe splits. Cruelly, the split often shows only when it thaws and the water starts moving again. Prevention in frost country is ordinary care: lag exposed pipes with foam insulation, disconnect and drain garden hoses and outdoor taps before a hard frost, let a tap trickle on the coldest nights so water keeps moving, and keep a little heat on if you are away. And know where your stop tap is, because a thaw is exactly when you will need it.

Heat is the quieter cousin. Pipes expand and contract every time hot water runs through them, and over years that repeated cycling works fittings loose and fatigues the material, a process called thermal fatigue. Long straight hot-water runs and pipes that see big day-to-night temperature swings take the worst of it. We cover the mechanism, the experimental evidence and how to design it out in a dedicated study, linked at the foot of this guide.

07 How a broken pipe gets repaired

There is a ladder of repair methods, from the small and local to the whole-run, and a good plumber picks the lowest rung that genuinely fixes the fault.

Spot repair or section replacement. For a single accessible failure, the plumber cuts out the failed length and joins in new pipe, using whatever joint suits the material: a compression or push-fit fitting, a soldered copper joint, a solvent-welded PVC joint. Right for one bad joint; wrong as a habit if the whole run is on the way out.

Pipe relining. For a buried drainage pipe that is cracked or root-damaged but still holding its shape, relining fixes it with no trench at all. A resin-saturated liner is drawn or inverted into the old pipe and cured in place (the method is called cured-in-place pipe, or CIPP), forming a smooth, jointless new pipe inside the old one. The lawn, the driveway and the paving stay where they are, which is both cheaper and far less destructive than digging.

Pipe bursting. When a pipe is too far gone to reline (collapsed, or it has lost its line), a bursting head is pulled through it, fracturing the old pipe outward while it draws a new HDPE pipe into the same path behind it. Still trenchless, apart from a small access pit at each end.

Full replacement or re-pipe. When an entire run has reached the end of its life (the tell-tale being one failure after another in old galvanised steel), patching individual leaks is spending good money on a lost cause. Re-piping the run in copper or PEX is the honest answer, and it is the moment to design the pressure and the layout properly so the next fifty years are quiet.

What good looks like, whichever rung it lands on, is the same in every case: the leak located before any wall or lawn is opened, a camera down a drain before anyone digs, and a repair that ends with a reason the pipe failed, not just a patch over the symptom. A finding is what stops it happening again.

08 When it is a licensed plumber's job

Water and drainage work in Australia is licensed work, and with pipes that is not red tape. Supply plumbing is under constant pressure, hot-water and gas systems sit right beside it, and the cost of a joint that looks fine and is not, hidden behind a wall, lands months later as rot and mould. Turning the water off and stopping a spray is yours; the repair, from the smallest soldered joint to a full re-pipe, is a licensed plumber's.

A burst that will not wait for business hours is the one case where speed genuinely matters, because every minute the water runs is more damage. For readers in Newcastle and the Hunter, the name we give when asked is Green Planet Plumbing's round-the-clock emergency team, who work the shut-off-and-make-safe sequence above and carry the leak-detection gear to find the concealed ones. Anywhere else, one question sorts an emergency plumber quickly: do you locate a leak before you open a wall? A plumber who answers "always" charges you for one hole instead of five.

One line belongs here for renters, because it is the most common broken-pipe question we are sent. In a rental, a burst or a leak is the landlord's to repair, and usually urgent repairs under your tenancy laws; your job is to make it safe, tell the agent or owner in writing straight away, and keep the photos. You are not expected to pay for a plumber to fix the building's pipes.

09 Questions, answered

+ The study behind this guide

One journal entry carries this guide's deeper dive, kept at its original address and date:

10 Check your symptom

The desk below covers this guide's territory: the pipes you can hear, the leaks you cannot see, and the pressure behind both. Pick what you are noticing for the mechanism and an honest severity read, then send us the specifics.