Understanding Why Pipes Fail
Every leak has a cause. Understanding why pipes fail helps you recognise the early warning signs, take preventive action, and explain to your insurer or plumber what is happening. Here are the eight most common reasons we find leaks in London properties, based on thousands of detection surveys carried out across the city.
1. Corrosion
Corrosion is the single most common cause of pipe failure in London homes. The capital's water supply is notoriously hard, with high levels of dissolved minerals that gradually attack copper pipework from the inside. Over years, this process creates pinhole leaks, tiny perforations in the pipe wall that weep small amounts of water continuously.
Pinhole corrosion is insidious because the leaks are so small that they do not produce any audible sound and the water volume is too low to register on a water meter. The first sign is usually a damp patch, mould growth, or staining on a wall or ceiling. By the time the damage is visible, the leak may have been active for months.
Galvanised steel pipes corrode even faster than copper, particularly once the protective zinc coating wears away. If your London property still has galvanised steel pipework, particularly in the cold water system, corrosion-related leaks are almost inevitable.
2. High Water Pressure
London's water supply pressure varies significantly by area. Properties at lower elevations or close to water mains can experience pressures well above the recommended maximum. While high pressure gives great shower performance, it puts constant stress on pipe joints, fittings, and appliance connections.
Pressure spikes are even more damaging. These occur when a valve closes suddenly, creating a shockwave in the pipework known as water hammer. You may hear this as a banging noise when a washing machine valve shuts off. Over time, these pressure surges weaken joints and can cause fittings to fail.
If your water pressure is consistently above four bar, consider having a pressure reducing valve fitted where the supply enters your property. This is a relatively inexpensive installation that can significantly extend the life of your plumbing system.
3. Frozen Pipes
London does not experience extreme winters by international standards, but it gets cold enough to freeze pipes in vulnerable locations. Pipes in unheated lofts, uninsulated external walls, garages, and outbuildings are all at risk when temperatures drop below freezing.
When water freezes, it expands by approximately nine percent. This expansion creates enormous pressure inside the pipe, often enough to split copper or crack plastic fittings. The damage typically occurs during the freeze, but the leak only becomes apparent when the ice thaws and water starts flowing through the split.
Every winter, we see a surge in emergency callouts across London in the days following a cold snap. The worst damage occurs in properties that have been left unoccupied and unheated, where burst pipes can flow unchecked for hours or days before anyone notices.
4. Poor Installation
A significant proportion of the leaks we detect in London properties can be traced back to poor installation. This includes soldered joints that were not properly heated or cleaned, push-fit fittings where the pipe was not inserted to the correct depth, compression fittings that were over-tightened or under-tightened, pipes that were not properly clipped or supported, and incompatible materials being connected without appropriate transition fittings.
Installation problems may not cause an immediate leak. A poorly soldered joint might hold for years before a pressure spike or slight building movement causes it to fail. A push-fit fitting that is barely engaged might work perfectly until the pipe shifts by a few millimetres.
5. Ground Movement and Subsidence
London sits on a variety of ground conditions, from London Clay in the south and west to sand and gravel in other areas. Clay soils shrink and swell with changes in moisture content, and this movement can stress buried pipes and foundations.
Trees are a particular factor. A mature oak or willow can extract thousands of litres of water from the soil in a growing season, causing significant shrinkage in clay subsoils. When the ground moves, underground pipes move with it, and rigid connections can crack or pull apart. We frequently find water main leaks in London properties where tree roots have caused ground movement near the pipe.
6. Age and Wear
Every material has a finite lifespan, and pipes are no exception. Copper pipes typically last forty to seventy years. Galvanised steel lasts twenty to fifty years. Lead can last over a hundred years. Plastic pipes are expected to last at least fifty years, though many have not been in service long enough to confirm this.
In a city like London, where many properties are well over a hundred years old, you may have pipes that have been in service for decades longer than their intended lifespan. Even well-maintained systems eventually wear out. If your pipework is approaching or exceeding its expected life, proactive replacement of the most vulnerable sections is cheaper than dealing with repeated emergency leaks.
7. Hard Water Scale
London's hard water causes limescale buildup inside pipes, particularly in hot water systems. This scale narrows the pipe bore, increases pressure drop, and creates turbulence that accelerates erosion corrosion. Scale also accumulates around valves and fittings, preventing them from sealing properly.
In extreme cases, scale buildup can restrict flow so severely that the increased velocity of water through the narrowed pipe causes rapid erosion at bends and tee fittings. We regularly see this in older London properties where the original fifteen millimetre copper pipe has been effectively reduced to ten or even eight millimetres by scale buildup.
8. Joint and Fitting Failure
Pipes themselves rarely fail in the middle of a straight run. The vast majority of leaks occur at joints, fittings, connections, and valves. These are the weakest points in any plumbing system, and they are subject to the most stress.
Solder joints can fail due to thermal cycling, particularly in heating systems where pipes repeatedly expand and contract. Compression fittings can work loose over time. Push-fit fittings can release if the pipe is subjected to lateral force. Rubber seals in valves and tap connectors harden and crack with age. Flexible hoses, commonly used to connect taps and toilets, have a limited lifespan and are one of the most frequent causes of sudden catastrophic leaks in London properties.
Replacing flexible hose connectors every ten years, regardless of whether they appear to be leaking, is one of the simplest and most effective leak prevention measures you can take. A five-pound hose replaced preventively is far cheaper than a five-thousand-pound water damage claim.
Prevention Is Always Cheaper
While you cannot prevent every leak, understanding these common causes helps you take practical steps to reduce your risk. Regular maintenance, appropriate water pressure, adequate pipe insulation, and proactive replacement of ageing components all make a significant difference. And if you suspect a leak, acting quickly always costs less than waiting.