Tracer dye testing
| Tracer dye testing | |
| Type | Test method |
|---|---|
| Applies to | Drains, gullies, pools and gravity systems |
| Detects | Where water introduced at one point emerges |
| Establishes | Connectivity and gross loss, not a precise leak position |
| Note | No statutory or standards definition of the technique |
Tracer dye testing introduces a coloured dye into a drain, gully, pool or other water system and observes where it emerges. It is used to establish connectivity, which run goes where, and to demonstrate gross loss from a structure. It is a confirmatory and mapping technique rather than a locating one: the dye shows that water travels from one point to another, or that it leaves a structure, but not the position of the defect it passed through. This article carries no citation for the technique itself, because it is defined by industry practice rather than by any statute or published standard.
How it is used[edit]
On drainage, dye introduced at one appliance or inspection point and watched for at another establishes which run serves what. This resolves misconnections, shared drains and unmapped runs, which is often the question that has to be answered before any condition survey means anything.
On a swimming pool or tank, dye released close to a suspected defect is drawn towards it if water is leaving there, which gives a visual confirmation at a fitting, a liner tear or a structural crack. Still conditions are essential: circulation, wind and bathers all move dye independently of any leak.
In leak investigation generally, it is used to confirm a suspicion cheaply before committing to a more involved method.
Limits[edit]
The technique shows an outcome, not a location. Dye that emerges at a downstream point has passed through everything in between, and dye that disappears has left the system somewhere along its length. Neither result identifies where. On drainage a CCTV survey and, where appropriate, a test to BS EN 1610 are what establish the condition and whether a length holds.[1]
Dye is also a visible marker that persists. On drainage and on pools this is usually acceptable, but on potable systems it is not appropriate, and the fittings requirements of the Water Supply (Water Fittings) Regulations 1999 include controls on substances in contact with water supplied for domestic use.[2]
See also
- CCTV drainage survey
- Pressure testing
- Tracer gas leak detection
- Water leak detection
- Borescope inspection
References
- ^BS EN 1610: Construction and testing of drains and sewers. BSI. Retrieved 2026-09-05
- ^The Water Supply (Water Fittings) Regulations 1999, Schedule 2: requirements for water fittings. legislation.gov.uk. Retrieved 2026-09-05