Water leak detection

Establishing that a leak exists[edit]

Detection begins by confirming loss rather than by searching. On a pressurised system the usual evidence is a pressure drop that does not stabilise, a meter that continues to register with all outlets closed, or a sealed heating system that needs repeated refilling. On a gravity system the evidence is more often damp or staining that appears in use rather than continuously.

Isolating sections in turn narrows the loss to a circuit before any method is applied to it. This step is what separates a survey from a search: methods applied to the whole property at once produce ambiguous results, and every method below performs better on an isolated run.

Methods[edit]

Acoustic listening detects the sound of water escaping under pressure through a pipe wall. Leak noise correlation compares that sound at two points on the same pipe and calculates the leak position from the difference in arrival time. Tracer gas introduces a safe gas mixture into a drained pipe and detects it where it escapes, which works where there is no pressure and no noise to hear. Thermal imaging reads surface temperature differences caused by moving water, and is qualitative rather than quantitative.^[1] Moisture meters and hygrometers map the extent and gradient of dampness in a material. Borescope cameras give direct sight of a void through a small access hole, and CCTV drainage cameras do the same for a drain run.

Ground penetrating radar and other utility location methods do not find leaks; they establish where the pipe is, which is often the precondition for applying a method to it.^[2]

Regulatory context[edit]

In England and Wales the installation and repair of water fittings is governed by the Water Supply (Water Fittings) Regulations 1999,^[3] which set requirements for the quality and suitability of fittings^[4] and detailed requirements in Schedule 2.^[5] Section 75 of the Water Industry Act 1991 addresses waste, misuse and contamination of water and gives water undertakers powers where water is being wasted.^[6] Guidance on the Regulations is published by Water Regs UK^[7] and product and material approval is operated under the WRAS scheme by Water Regulations Approvals Scheme Limited.^[8]

Non-invasive practice[edit]

The purpose of the discipline is to reduce the area that has to be opened up. A method that narrows a leak to a square metre before any floor is lifted removes most of the cost and disruption of the repair, and this is the basis on which insurance policies commonly cover trace and access work separately from the repair itself.

Verification with a second method is normal practice where access allows, because each method has characteristic false positives: acoustic signals travel along pipes and can be heard some distance from the escape, thermal patterns can be produced by pipework that is not leaking, and moisture readings show where water has arrived rather than where it left the pipe.

Practice at ADI Leak Detection[edit]

ADI Leak Detection is the subject of this wiki and carries out this work across England, Scotland and Wales.^[9] Its published approach follows the sequence described above: the company states that every investigation ends in a written report by the attending engineer, supported by photographs and video and formatted for trace and access and escape of water insurance claims.^[9]

ADI publishes six detection technologies of its own — tracer gas, acoustic listening, thermal imaging, leak correlation, borescope cameras and moisture meters — and names pressure testing, dye testing, CCTV drain survey, underwater inspection and drone inspection against particular services.^[9] The company reports around 5,000 jobs a year.^[9] Coverage and the engineers who carry the work out are described in the county and engineer articles on this wiki.