Technical briefing 2 – leak detection

Hidden water leaks can be hard to find and many traditional techniques are invasive and cause damage, e.g. removing tiles or removing walls. Water leaks and moisture infiltration can cause serious damage to a house or building and can be difficult to detect until it’s already too late.

There are many sources of building moisture including humidity, condensation, pipe leaks, rain and snow, and even people and animals breathing. Usually a low level of moisture is fine, but leaks or heavy condensation can cause serious problems.

Water leak detection is a complex task that requires a mix of modern technology and expertise. Modern water leak detection companies such as Revival use the latest technology like thermal imaging cameras and gas tracers which, along with many years of training and expertise, ensure that even the most hidden water leaks can be detected with minimum damage, inconvenience and expense.

This technical briefing explains the different types of leak detection equipment and techniques available and the advantages and disadvantages of each.

Trace and access

Trace and access is a general term used within the insurance industry to cover all sorts of leak detection activities. Insurers offer leak detection cover in their trace and access policies as an add-on to the main policy as finding a leak is often expensive and causes a lot of damage.

Too often a “trace and access” mind-set is used by insurers and suppliers when it comes to finding leaks – “trace” the likely source of the leak then “access” the pipework by damaging the property to see if they are right. They often rely on acoustic methods – literally listening for the leak. This requires an understanding of the different types of sounds water leaks make, the various factors affecting the sounds, how the sounds travel down pipes, and how the sounds travel through mediums such as soil and brickwork.

However, well qualified and experienced suppliers using the right equipment can find pretty much any leak without causing unnecessary damage. They have a range of tools at their disposal and will know when to use the right equipment.

Moisure meters

There are two types of moisture meters which are commonly used – pin-type meters and pinless meters. They are ideal for detecting moisture in wood.
 
With pin-type meters the pins of the meter are pushed into the material being checked. These meters then measure how much resistance there is to an electrical current between the pins to determine the moisture content of the material. As wood is a natural insulator and water is an electricity conductor, a low resistance will indicate the presence of moisture. Drier wood will show more electrical resistance.
 
Advantages of pin-type meters:

  • The two pins allow for testing both shell and core depths to measure the moisture present.
  • Readings are very reliable.
  • Uneven surfaces can be measured easily.
  • It can be used to effectively distinguish surface and ambient material conditions.

Disadvantages of pin-type meters:

  • They measure only between the two pins.
  • The pins are easily breakable.
  • They cause damage to the surface leaving pinholes.

Pinless meters measure a wood’s moisture level using an electromagnetic signal. Since they don’t poke holes in the wood they’re good for measuring the moisture level in fine furniture and expensive hardwood floors. They are sensitive to variations in wood density (also referred to as specific gravity), and as different types of wood have different densities, technicians have to make sure the meter is set to the correct specific gravity setting before measuring.

There are pinless meters that can test for moisture in materials other than wood, such as concrete.

Advantages of pinless meters:

  • Quick scanning of large areas – the technician just presses the sensor plate onto the material, takes the reading, lifts and repeats the measurement.
  • As it is a quick and fast measuring process more results can be collected to calculate an average result.
  • They don’t leave pinholes.
  • They can be used on materials other than wood.

Disadvantages of pinless meters:

  • If the surface is too small or uneven there may not be enough space for the sensor plate.
  • They can scan only to a fixed depth, and if the material is too thin or too thick the pinless moisture meter cannot identify the source of moisture accurately.
  • Metal objects interfere with the electromagnetic radio waves sent out by a pinless meter.
  • Moisture on the surface of the material can alter the readings.

The technician will need to take multiple readings to get an overview of the wood’s moisture content. This is much harder to do when using a pin meter because pin meters only measure the moisture content between the two pins and nowhere else, so the technician needs to take far more measurements to approximate what a pinless meter can easily do in one quick scan. And each reading with a pin meter requires poking two new holes in the wood.

A pinless moisture meter uses a large sensor pad and emits electromagnetic signals to measure the moisture content of the wood. This allows the technician to scan large areas quickly and accurately and get instant moisture meter readings – he or she can scan many board feet in just seconds without the time-consuming effort of driving pins into the wood.

Thermal imaging cameras

Using a thermal imaging camera under the right circumstances it’s possible to find hidden water and moisture issues without resorting to destructive testing. Thermal imaging cameras identify very small differences in temperature on the surface of different materials, highlighting the warmer and the colder surface areas to provide evidence of where the leak is originating.
 
Moisture tends to cause only subtle heat differentials. A thermal camera capable of detecting moisture needs to have high resolution and great thermal sensitivity, so that small temperature differences are displayed. The camera detects the emitted thermal energy of an object – where moisture is present the thermal image will show as cold spots on the camera.
 
Thermal cameras can help locate water and approximate the moisture extent but identifying a pattern that looks like moisture does not guarantee the presence of water. There are many reasons why a camera shows temperature differentials besides moisture in the walls, so a moisture meter should always be used to confirm what the thermal camera has detected.
 
Advantages of thermal imaging cameras:

  • Their advanced features make it possible to scan quickly large areas.
  • They are non-invasive.
  • They speed up the surveys with the automated humidity alarms.
  • They include software to support creating reports quickly.

Disadvantages of thermal imaging cameras:

  • When temperatures are very close in range thermal cameras can lead to misleading information.
  • They only allow the measurement of the surface temperature.
  • They have to be used in conjunction with moisture meters.

Revival South West recently used thermal imaging very effectively to find a leak in a property which was preventing the customer from using the water within the property and within their holiday let next door (which was occupied). They found the leak using a combination of thermal imaging, acoustics and a borescope with such precision that they were able to open up the ceiling void in exactly the right place to expose a leaking ballofix isolation valve. The valve was changed allowing the customer to get the water back on in their own home and their holiday let next door.

Tracer gas testing

Tracer gas testing equipment is often used when all other leak detection methods have failed. The kit is expensive but it does deliver results quickly and accurately.

The tracer gas, a mixture of hydrogen (5%) and nitrogen (95%), is introduced into the pipe or water system with the suspected leak. As hydrogen is the lightest and smallest molecule in the atmosphere it will exit the pipework at the leak and make its way to the surface (permeating through all materials including concrete, tarmac, block paving and grass) where it is detected using gas sensitive probes. The tracer gas is completely safe to use in drinking water supplies as it is non-toxic and non-corrosive.

The process is quite involved and any technician using gas tracer equipment must have appropriate training. The pipe or water system with the leak has to be drained out as much as possible, although small amounts of water remaining at low points of the system do not dramatically affect the success as the gas is pressurised around the water system. The system or pipe must then be sealed so no gas can escape except via the leakage point. The gas is introduced to the system or pipe based on the normal operating pressure of the system being tested and how high the technician wishes to pressurise. When the gas cylinder’s pressure gauge steadies the technician knows that any subsequent pressure loss of tracer gas can only be via a leak. The gas detecting probes will then detect the gas at the point at which it is leaking.

Revival recently used tracer gas leak detection on an external mains pipe leak. The customer had water bills adding up to more than £20,000 over the course of three years and other contractors had attempted to find the leak but hadn’t been successful. Revival found the leak using tracer gas and acoustics and arranged for the leak to be excavated on behalf of the insurer.

Summary

There are a range of techniques and equipment available to trained technicians to make leak detection an efficient an unintrusive way of finding leaks. Understanding which is the best method to use requires years of experience and training, but an appreciation of how they work is useful for insurers and loss adjusters wanting a cost effective and timely solution to a leak

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