Pressure testing is a diagnostic method used to assess the integrity of a pressurised pipe system. It helps determine whether the system is losing water or pressure and provides valuable information that guides the rest of the leak investigation.
Pressure testing is carried out using specialist pressure testing equipment appropriate to the system being investigated. Depending on the application, this may involve hydraulic or pneumatic test equipment designed to safely pressurise and monitor the pipework.
It is one of several techniques used during leak investigations. The most appropriate method depends on the type of leak, the pipe material, the construction of the property and the evidence available on site. To explore related techniques, visit our Leak Detection Technology page. You can also view our main Leak Detection service page for a wider overview.
What Pressure Testing Is
Pressure testing is used to assess whether a sealed pipe system is maintaining pressure as expected. If pressure falls under controlled test conditions, it may indicate that the system is losing water through a leak.
Pressure testing is commonly used on mains water supplies, domestic plumbing systems, central heating systems and other pressurised pipework.
Although pressure testing can confirm that a problem exists, additional investigation is usually required to determine the location of the leak.
How Pressure Testing Works
The pipe system may be isolated, monitored or pressurised under controlled conditions depending on the type of system being investigated. Specialist pressure testing equipment is used to observe how the system behaves over time and whether it maintains pressure as expected.
The rate at which pressure falls can also provide useful information. A rapid pressure loss may indicate a larger or more active leak, while a slow pressure drop may suggest a much smaller leak or one that only occurs under certain conditions. This helps guide the investigation and indicates what type of leak is likely to be present.
- The system is prepared for testing.
- Pressure is measured using suitable equipment.
- The system is monitored over a controlled period.
- Any pressure loss is assessed.
- The findings are interpreted alongside other evidence.
Pressure testing provides evidence about the condition of the system rather than the exact location of a leak.
Isolating Different Parts of the System
Pressure testing can also help narrow down which part of a system is losing water. Where suitable isolation points are available, different sections of the pipework may be tested individually.
For example, it may be possible to test hot and cold water systems separately, isolate different heating circuits or distinguish between internal plumbing and an external supply pipe. By comparing the results, the investigation can often be focused on a much smaller area before specialist leak detection equipment is used.
This structured approach helps reduce unnecessary investigation and guides the next stage of leak detection.
When Pressure Testing Is Most Useful
Pressure testing is particularly useful where there is uncertainty about whether a system is actually leaking.
It is commonly used for:
- Central heating systems losing pressure.
- Suspected mains water leaks.
- Underground water supply pipes.
- New pipe installations.
- Pipework that has been repaired.
- Investigations where a hidden leak is suspected.
What Pressure Testing Can and Cannot Tell You
Pressure testing can confirm whether a system is maintaining pressure or losing it. It can also indicate whether the water loss appears to be rapid or gradual, helping the investigator understand the likely severity of the leak.
In many cases, pressure testing can also help narrow down which part of the system is affected before more targeted leak detection methods are used.
However, pressure testing does not normally identify where the water is escaping. Additional investigation is usually required to establish the location of the leak.
Why Pressure Test Results Need Interpretation
A drop in pressure does not automatically confirm the type, size or location of a leak. System design, temperature changes, trapped air and testing conditions can all influence the results.
The pattern of pressure loss can also influence which leak detection methods are used next. A system losing pressure rapidly may behave very differently to one losing only a small amount of water over many hours or days.
An experienced leak investigator considers these factors before deciding what further testing is required.
Pressure testing provides evidence about system performance. The findings still need to be interpreted within the wider context of the investigation.
What Affects Pressure Testing Results?
- System temperature.
- Pipe material.
- Trapped air within the system.
- Testing pressure.
- Duration of the test.
- The size and behaviour of the leak.
- Whether the system has been correctly isolated.
Understanding these factors helps ensure the results are interpreted correctly.
How Pressure Testing Fits With Other Leak Detection Methods
Pressure testing is often used before or alongside other leak detection technologies.
- Acoustic Leak Detection to investigate pressurised leaks.
- Tracer Gas Leak Detection where a leak has been confirmed but its location remains unknown.
- Correlation Leak Detection on suitable underground pipe systems.
- Thermal Imaging Leak Detection where temperature changes may provide supporting evidence.
- Moisture Mapping to assess how escaped water has spread through the property.
The aim is not simply to measure pressure. The aim is to understand what the pressure readings mean and how they guide the next stage of the investigation.
Why Pressure Testing Matters
Pressure testing helps confirm whether a leak investigation is necessary and provides valuable information about the condition of the system before more targeted leak detection methods are used.
When interpreted correctly, it helps guide further investigation while avoiding unnecessary work.
Frequently Asked Questions
Can pressure testing find a leak?
Pressure testing can confirm that a system is losing pressure, but it does not normally identify where the leak is located. Additional leak detection methods are usually needed to pinpoint the source.
What does pressure testing show?
Pressure testing shows whether a sealed pipe system is maintaining pressure or losing it under controlled conditions. It can also indicate whether the water loss appears to be rapid or gradual, helping guide the next stage of the investigation.
Can pressure testing tell how big a leak is?
Pressure testing cannot measure the exact size of a leak, but the rate of pressure loss can indicate whether the leak is likely to be relatively small or more significant. This helps investigators decide which leak detection methods are most appropriate.
Why is pressure testing used before leak detection?
Pressure testing helps confirm that a system is losing water before more detailed leak detection methods are used. It can also help narrow down which part of the system is affected, allowing the investigation to be planned more effectively.
Need Help With a Hidden Leak?
Every leak investigation is different, and no single technology is suitable for every situation. The most effective approach depends on the type of leak, the pipe material, the construction of the property and the evidence available on site.
To learn more about hidden leak investigations, visit our Leak Detection hub page. If you need advice about a suspected leak or would like to discuss an investigation, please contact us and we will be happy to help.
