Pressure testing
| Pressure testing | |
| Type | Test method |
|---|---|
| Applies to | Pressurised pipework and, by adaptation, drains |
| Standards | BS EN 806-4 (installations in buildings); BS EN 1610 (drains and sewers) |
| Establishes | Whether a system holds, not where it leaks |
| Media | Water or air |
Pressure testing establishes whether a length of pipework holds pressure over a defined period. The section is isolated, filled and raised to a test pressure, and the pressure is then observed against a permitted drop for a set duration. It answers a different question from leak detection: a pressure test proves that a system is or is not losing water, while a detection method finds where. Testing is normally the step that precedes detection and the step that verifies the repair afterwards.
Method[edit]
The section under test is isolated with valves or test plugs, filled and vented so that no air remains, then pressurised to the specified test pressure and held. A gauge is observed over the prescribed period and the drop compared against the permitted allowance. BS EN 806-4 sets out installation requirements for pipework inside buildings conveying water for human consumption, including testing.[1]
Venting matters more than it appears to. Trapped air compresses and expands with temperature, producing a falling gauge on a sound system and a stable one on a leaking system that is being topped up by expansion. Temperature change during the test period has the same effect and is the usual reason a test has to be repeated.
Isolation and sectional testing[edit]
Because the test says only that something within the isolated section leaks, the value of the result depends on how small the section is. Testing a whole property proves only that the property leaks. Progressive isolation — closing valves in turn and retesting — reduces the leaking section until it is short enough for a detection method to be applied efficiently.
On a sealed heating system, filling loop and expansion vessel behaviour has to be accounted for, since a failed expansion vessel can produce pressure loss that is not a leak at all.
Drains[edit]
Gravity drains are tested differently, with water or air, under BS EN 1610, which covers construction and testing of drains and sewers.[2] A drain does not normally operate under pressure, so the test creates a condition the pipe does not usually experience; a length that fails an air test is not necessarily leaking in service, and confirmation with a water test or a CCTV survey is usual before work is specified.
See also
References
- ^BS EN 806-4: Specifications for installations inside buildings conveying water for human consumption. Installation. BSI. Retrieved 2026-09-05
- ^BS EN 1610: Construction and testing of drains and sewers. BSI. Retrieved 2026-09-05