What Causes Pipes to Burst? (And How to Prevent It)

Quick answer

The 6 most common causes of a burst pipe in South Africa:

1. High water pressure — most municipal supply runs at 400–600kPa; pipes burst above 800kPa
2. Corrosion — old galvanised steel pipes from the 60s–80s, still in many homes
3. Frost in Free State, Highveld, KZN Midlands and Eastern Cape interior
4. Water hammer — sudden valve closures (washing machines, dishwashers) stress old joints
5. Tree roots crushing buried supply pipes
6. Physical damage — DIY screws into walls, garden tools hitting buried lines

1. High water pressure

Municipal supply in SA varies wildly by area. Mountain suburbs (Constantia, Houghton) often run high pressure (600–900kPa). Pipes and fittings are rated for 400–800kPa.

Prevention:

• Fit a pressure-reducing valve (PRV) at the house entry — set to 400–500kPa
• Cost: R900–R2,500 installed
• Mandatory in most municipalities under SANS 10252

You'll know your pressure is too high if:

• Taps hammer when you turn them off
• The geyser overflow drips constantly
• Mixer taps spray unevenly
• You blow more washers than seems normal

2. Corrosion

Galvanised steel pipes corrode from the inside. After 30–50 years, the wall thickness drops below safe limits and they split or pinhole.

Common in: homes built between 1950 and 1985, especially in coastal areas.

Signs:

• Brown or rusty hot water
• Reduced water pressure on one fixture
• Visible rust stains on exposed pipe sections
• Recurring small leaks on the same line

Fix: re-pipe in copper or PEX. Cost R8,000–R30,000 for a full house, depending on size.

3. Frost damage

Less common in SA than the UK or US, but real in:

• Free State (Bethlehem, Bloemfontein)
• Highveld (Johannesburg, Pretoria, Polokwane)
• KZN Midlands
• Eastern Cape interior (Queenstown, Aliwal North)
• High-lying Western Cape towns (Sutherland, Ceres)

Water expands 9% when it freezes. An ice plug in a pipe doesn't usually split the pipe at the ice — it splits it downstream where pressure builds.

Prevention:

• Lag exposed pipes with foam insulation (R25/m at Builders)
• Drain garden taps and outside hoses before winter
• Open cabinet doors under sinks against an outside wall in extreme cold so warm air circulates
• Let one tap drip in the coldest weeks — moving water doesn't freeze easily

4. Water hammer

When you close a valve fast (washing machine fill valve, dishwasher solenoid, lever mixer slammed shut), the moving water stops suddenly and the pressure spike travels back through the pipes. Old joints fail at the weakest point.

Signs:

• Loud "bang" or "thump" when an appliance finishes filling
• Pipes rattling in the walls
• Cracks at solder joints

Fix:

• Install water-hammer arrestors (R350–R600 per fixture) on the washing-machine and dishwasher supplies
• Fit slow-closing valves where possible

5. Tree roots

Roots are drawn to the moisture and air around buried pipes. They enter at joints and over years swell to crush the pipe.

Common offenders: willow, fig, jacaranda, eucalyptus, oak — anything with aggressive roots, planted within 5m of a service line.

Signs:

• Recurring main-drain blockages at the same spot
• Mysterious wet patches in the garden over the supply line
• Reduced water pressure throughout the house
• Sinkhole or dip in the lawn over a known pipe run

Fix: dig and replace the affected section. Cost R5,000–R20,000.

6. Physical damage

The classic story: you drill a hole in a wall for a picture and you've gone through a pipe. Or you dig in the garden and hit a buried supply.

Prevention:

• Use a pipe detector (R450 at Builders) before drilling into walls in a kitchen or bathroom
• Locate your buried services before garden landscaping
• Don't park vehicles over shallow buried services

Annual maintenance to prevent bursts

1. Check the geyser overflow — if it's dripping, the pressure valve is failing (R450 fix vs R30k flood)
2. Pressure test — a plumber can fit a gauge in 5 minutes and confirm your house pressure
3. Inspect exposed pipework — chrome basin pipes, geyser pipework — for any signs of corrosion or weeping
4. Insulate before winter if you're in a frost area
5. Service old galvanised pipes — get a plumber to assess if you're due for re-piping

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