Water leak detection guide

Leak detection is a vitally important process for safeguarding properties against water leaks. This Catalyst Services UK guide explains how they happen and how water leaks can be detected.

What is a water leak?

A water leak is an uncontrolled release of water, usually from a water pipe, water tank or other asset, such as a tap, bath, or shower.

What is the extent of water leaks in the UK?

Many millions of litres of water is lost every day in the UK due to leaks. The main cause is faulty water mains. However, huge amounts of water are lost in homes and businesses.

Plumbing accreditation body WaterSafe says a leaking toilet cistern can waste up to 400 litres of water a day – enough to fill five baths and more than double a family water bill.

Water company Severn Trent believes up to 8 per cent of toilets – most of them dual flush ones – are leaking at any one time.

This cause of leaks alone adds up to 400 million litres of water lost a day, enough to supply the populations of Edinburgh, Bristol, Manchester, Sheffield, Cardiff, Liverpool and Belfast combined!

What is an internal water leak?

An internal water leak is one that occurs inside a property. As such, it may be caused by a faulty water pipe (but not a water supply pipe) or another water-related asset, such as a tap, kitchen appliance, bath, shower or water tank.

What is an external water leak?

An external water leak is one that occurs in water pipes and related assets outside the property. For example, there could be a leak in the water supply pipe that runs from the stopcock, usually located on the boundary of a property.

Or an external leak could occur in the water communication pipe taking water from the water main to the water supply pipe. Finally, an external water leak could occur in the water main itself.

What are the main causes of internal water leaks?

There are many different ways internal water leaks can be caused. They include:

  • Pipes, joints, and valves that have deteriorated and become worn out over time. For example copper pipes may have corroded or cracked, plastic pipes can also fail over time.
  • Broken seals and other fittings in appliances, such as washing machines and dish washers.
  • Blockages in pipes and in appliances that build up pressure, forcing water through weak joints and seals.
  • Damage to water pipes, for example on radiators, caused by knocks, which can weaken joints.
  • Fluctuating temperatures and pressures affecting the pipes, joints and seals in pipes and other water systems.
  • In extremely cold weather, water can freeze in pipes. The expanding ice can cause them to burst.
  • Blockages in, or damage to, pipes serving water tanks can be particularly devastating as they can release large volumes of water under significant pressure.
  • Accidental damage to pipes while doing DIY – for example by putting a nail through a water pipe embedded in a wall.

What are the main causes of external water leaks?

Over the years, external water pipes have been made from a range of materials, most notably copper, cast iron, steel and, most recently, plastic – namely medium density polyethylene or MDPE, which is usually light blue in colour.

  • Cast iron and steel pipes can corrode over time, resulting in thinning of the pipe wall and, eventually cracks or holes forming, allowing escape of water.
  • Copper pipes can also corrode, especially if a low quality copper has been used.
  • As with internal leaks, joints can also fail over time, allowing water to leak out.
  • Copper and plastic pipes are flexible. This can result in them moving in the ground, especially if located below roads or drives where the action of vehicles can cause vibration or compression of the ground. This regular movement can disrupt joints or cause splits in the pipe material.
  • This process can be made worse by the presence of stones or rocks that can rub against the pipes over time, resulting in tiny cracks or holes.
  • This process can be made worse if pipes are not laid properly.
  • Ground movement can also disrupt pipes, resulting in cracks, holes or joints being broken.
  • As with internal pipes, changes in ground temperature can contribute to the processes described, especially if water pipes are laid close to the surface.
  • Changes in water pressure can act on weakened pipes and pipe joints increasing the risk of leaks.
  • Work carried out on homes, either by contractors, or by DIY or gardening enthusiasts, can disrupt water supply pipes, increasing the risk of leaks occurring in the future or directly causing them.

What kinds of damage can water leaks do?

Water supply pipe leaks can be highly damaging for a number of different reasons.

Major water leak flooding

If there is a catastrophic release of water in the home due to the sudden failure of a water pipe, many hundreds, if not thousands, of gallons of water can escape very quickly, flooding the property.

If the water leak is caused by a defective pipe or tank in the loft, the whole house can be flooded.

Hidden water leak damage

Water leaks can also occur over longer periods – days, weeks or month – with water seeping into building substrates. This can result in hidden damage to walls, floors and ceilings.

Damage may not be immediately apparent but can still be substantial. For example wooden floorboards, joists and lathe can be affected by rot.

After being soaked in water for a long period, plaster and brick mortar can be loosened and severely weakened. Walls, floors and ceilings can be badly affected by mould growth.

Over time, these hidden leaks can cause major cracking in walls and ceilings and severe damage to floors.

Structural damage and subsidence

Water leaks can also undermine and weaken whole structures by washing away material within and around foundations. Soils saturated by water from leaks can be weakened. As a result, foundations may give way and subside.

Are water leaks a health hazard?

Water leaks can be a significant health hazard. This is because water can cause damp conditions and moisture build up in homes, which can increase the risk of respiratory, skin and eye disease.

Damp walls and ceilings can trigger mould growth. Mould spores can also contribute to infections and trigger other illnesses.

A study published in BMJ Journals concluded that the risk of asthma, allergic rhinitis, and atopic dermatitis was higher in homes that had visible mould, damp stains or water damage. Of the respiratory infections, the risk of common colds was most clearly increased.

As reported in an article by Catalyst Managing Director Brad Jackson, housing landlords are increasingly concerned as a results of high-profile cases where asthma and chest infections related to damp and mould in homes have been linked with the deaths of vulnerable people, including children.

How easy are water leaks to detect?

The source of a sudden and catastrophic water leak is likely to become apparent very quickly. However, if the source is deep inside a wall, under a structure, or in an underground pipe away from a property, its precise location may be more difficult to detect.

Identifying the precise location of a leak is a key task, once the water supply has been turned off. Only then, can a solution be put in place, usually in the form of a pipe repair or replacement.

If the source of the water leak is in a hard-to-reach place, locating it precisely is essential to ensure the leak is resolved as quickly as possible at the lowest possible cost.

What are the signs of water leaks?

  • Hissing sounds, or possibly dripping sounds, coming from walls and floors may be caused by escaping water.
  • Damp patches and cracks in walls, ceilings and floors.
  • Mould growth.
  • Musty smells.
  • A drop in water pressure, so taps run slowly.
  • An inexplicably lush lawn.
  • Damp patches on drives or boggy flower beds.
  • A sudden increase in water bills.
  • A water meter turning when no water is being used.

Who is responsible for detecting water leaks?

The system of water pipes that deliver clean water to homes and businesses are owned and controlled by various parties.

Water utility companies are responsible for water mains (also known as the main carrier pipe) in the areas they serve.

Water is then taken from the main to the boundaries of homes and businesses in a water communication pipe. Water companies are also responsible for these pipes.

Water supply pipes then take the water from the property boundary to the inside stop valve in individual homes and businesses. If parts of these supply pipes serve more than one home, homeowners may have shared responsibility for them.

Internal pipes that take water from the internal stop valve around the property are the responsibility for the property owner, who could be a homeowner or a landlord.

Therefore, each of these parties are responsible for maintaining their sections of pipes and, therefore, detecting leaks along them.

Will detecting water leaks damage my property?

If water leaks occur in pipes that are embedded in walls or floors, one way to detect the leak is to uncover the pipe by removing substrates, such as plaster, brickwork or concrete.

This ‘destructive’ method for locating a leak may be unavoidable in some cases. However, there are many new ways to detect water leaks that combine smart technology and the skill and knowhow of experienced operatives to locate leaks without having to cause such damage.

These methods are called non-destructive or non-invasive water leak detection. They are often quicker, more accurate and less costly than conventional destructive methods.

What are the main methods of water pipe leak detection?

Visual inspection

Finding water leaks is a bit like detective work. Experienced clean water engineers know what to look for and can see tell-tale signs that others often miss.

Therefore, the first task is to carry out a visual inspection of the property, looking for signs of leaks, including how water is travelling through structure substrates. This will help locate the source of a leak.

Damp meter detection

Damp meters, also known as moisture metres, are very helpful for detecting damp in walls, floors and ceilings that could indicate there is a water leak in a property.

Types of damp that can be identified include: penetrating damp, caused by water seeping through walls; condensation damp, caused by moist air; and rising damp, caused by ground water.

Thermal imaging

Thermal imaging camera can be used to locate leaks in both hot water and cold water pipe systems. The infrared thermal imaging cameras record and display thermal images of structures.

By doing so, they can detect anomalous changes in temperature that identify areas that are affected by cold or hot water leaks hidden inside walls, floors and ceilings.

They can also detect moisture that indicates the presence of leak that would otherwise go undetected by a moisture meter.

thermal imaging leak detection

Acoustic profiling

Acoustic profiling uses highly sensitive microphones to identify the noise created by a water leak that many be many feet underground or under buildings. Advanced acoustic software enhances the sound and helps pinpoint its source.

This helps water supply engineers to devise the most effective methods for either repairing the leak or bypassing it.

Tracer gas analysis

Tracer gas analysis works by introducing gas into a water pipe which is buried underground. The gas escapes from the pipe at the point of the leak and rises to the surface, where it is picked up by highly-sensitive gas sensors.

Hydrogen gas, combined safely inert nitrogen is used/. Tracer gas analysis can accurately and quickly locate a leak along a long run of water pipe, even when buried under concrete and asphalt, preventing the need for costly excavation.

Correlation leak detection

Correlation leak detection also uses sound to locate a water leak. Two detectors are placed close to the suspected location of the leak.

They detect the frequency of the sound created by the water leak. By comparing the signal delay, sensor distance and the sound velocity, data from the two detectors can be used to correlate the location of the leak.

Dye leak detection

A simple, non-toxic water soluble dye can be used trace the flow of water through a system. Identifying where the dye is found in the system helps locate leaks.

Inspection cameras

Water supply engineers use a range of digital inspection cameras to record video footage inside pipes to look for signs of damage that indicate a source for a leaks.

The mini camera systems, with a miniature camera on the end of a flexible cable, can also be used to inspect hard-to-reach pipework to identify damage of tell-tale signs of escaping water.

Pipe tracing

Where there are no up-to-date plans showing the location of water supply pipes, they may have to be traced before the location of a leak can be detected.

Two key methods for tracing water pipes passively, without the need for expensive and disruptive excavations, are using a cat and sonde and ground penetrating radar.

Cat and sonde pipe tracing

A sonde is a transmitter which is sent along a pipe from a known point. This is detected by the cat carried on the surface by the clean water technician.

Ground penetrating radar

A ground penetrating radar system detects underground utilities, including water pipes, by transmitting radio waves through the ground. When they hit a water pipe they are bounced back to a receiver, allowing the pipe to be detected.


How can water leaks be repaired?

Once a water leak is detected, there are a number of ways repairs can be carried out. In the main, internal leak repairs will be carried out by a plumber. Meanwhile, external water leaks will be repairs by a team of water supply pipe technicians.

What is a water pipe point repair?

A point repair is carried out to repair a leak in one discreet location. It may involve excavating a pipe. A short section of pipe may be replaced or specialist clamps fitted over a damaged pipe to cover the hole causing the leak.

What is water pipe moling?

Where a significant section of water pipe needs to be replaced, a common and effective method is to carry out moling. Compressed air is used to force a moling head through the soil. A new water pipe can then be inserted in the underground channel created. This reduces the scale of excavation needed to cure the leak.

What is water pipe moling?

Where a significant section of water pipe needs to be replaced, a common and effective method is to carry out moling. Compressed air is used to force a moling head through the soil. A new water pipe can then be inserted in the underground channel created. This reduces the scale of excavation needed to cure the leak.

water pipe mouling, and re-routing

What is water pipe re-routing?

If a water pipe is in a hard-to-reach location or it is deemed that the pipe is so degraded that it is at the end of its life, it could be best to reroute the water supply through a new pipe. The pipe can be installed in a way that access points for easy ongoing maintenance can be included.

What is water pipe replacement?

As with water pipe re-routing, where a water pipe has seriously deteriorated or is made of material that is no longer meets regulatory standards, it is likely to be best to replace it.

How do you assess the extent of damage caused by a water pipe leak?

Assessing the impact of a water leak on a structure is an important first step to taking measures to rehabilitate structures that have been adversely affected.

This is an important part of making an insurance claim following a water leak.

Key elements of the assessment process will be:

How do you assess the extent of damage caused by a water pipe leak?

Assessing the impact of a water leak on a structure is an important first step to taking measures to rehabilitate structures that have been adversely affected.

This is an important part of making an insurance claim following a water leak.

Key elements of the assessment process will be:

  • The location of the water leak – if it occurred in a loft or on upper floors, water may have seeped through walls and ceilings to lower floors.
  • Related to the point above, the extent of the water leak – how far it has spread in a building.
  • What structures and items the water has come into contact with – for example furniture, electrical products, wall coverings and delicate flooring.
  • How long the leak has lasted before being detected. This will help assess the potential impact of the water on different materials, for example different wall substrates. These could be plaster, wood, tiles, and mortar.
  • If clean flood water has been left to stand for a long period, it has to be treated as wastewater, increasing the cost of both property rehabilitation and water disposal.
  • The potential health impacts of the presence of flood water in structures – for example, long-terms risks associated with damp and mould development.
  • The viability and cost of using different methods to dry surfaces and substrates – for example, dehumidifiers and air movers – including the length of time they will have to be used.
  • The need to strip away materials affected by leak water. This could include: removal of wallpaper, tiles, plaster and plasterboard, and brick mortar.
  • The need for specialist sanitation procedures to clean surfaces and deal with potentially harmful materials – and for odor control to remove smells associated with flood water.

What can householders do to find leaks and save water?

As has been made clear in this guide, the key to identifying wasteful and potentially damaging water leaks is vigilance and knowing what you are looking for.

Water companies are very keen to reduce water waste, so many provide free advice and, in some cases, aids for detecting water leaks, such as toilet leak detection strips.

These are paper strips that change colour when in contact with water, so pick up otherwise hard-to-detect low-volume water flows from cisterns into toilet bowls.

For more information on advice and aids, go to your local water company’s website, or go to the website of Safe Water Save Money, an organisation that works with many water companies to provide free or subsidises water saving devices.

In most cases, it is advisable to seek expert help. For example, internal water leaks associated with appliances and heating systems should be dealt with by a qualified plumber and/or heating engineer.

External leaks should be investigated by a water supply pipe surveying, repair and installation specialist. It will have the expertise and equipment described in this guide to detect leaks and put in place the right solutions.

Find out more

Catalyst Services UK provides leak detection and water supply pipe repair and replacement services for the insurance industry, plus commercial and domestic customers.

Its other services include: CCTV drainage surveys; drain and sewer cleaning; drain repair and rehabilitation; off-mains drainage maintenance and replacement (septic tanks, water treatment plants); subsidence investigation; and home emergency services.

Talk to Catalyst today. Telephone 0800 870 8080. Email: [email protected].

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