Underground ducting colour codes explained


Underground ducting must be colour-coded legally to comply with safety and building regulations. This is to ensure that when excavating there’s no damage to the cables as they’re housed in ducting. Ducting also serves as a warning sign as to what cables you may be accidentally interfering with so you can act accordingly. It’s important to know and to adhere to the UK’s universal ducting cable colour codes.

There are minimum depth requirements for all underground utility ducting. For example, mains gas cables must be buried at least 750mm beneath a public footpath or highway. It’s worth checking with HSE or a utility provider on minimum depth requirements.


Colour Use
Black Domestic mains electric cable, low voltage
 Red High voltage electric cable
Yellow Service and mains gas cable (ducting is perforated to allow for gas venting)
Blue Water pipes installed at least 750mm below surface
Green Broadband, telephone and non-motorway CCTV cables
Grey BT or telecommunications cables
Purple Motorway service cables for speed cameras, traffic cameras, emergency phones etc
Orange Street lighting and traffic signaling cables (i.e. traffic lights)

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