Spot & Line Marking Paint Colours: What Do They Mean?

Chances are you’ve seen a bunch of different markings on the ground with different colours and symbols but haven't taken the time to stop and think about what they actually mean.

Site workers, managers and engineers needed a way to tell where utilities were located beneath the surface of the ground and what they were. Thanks to the Australian colour coding system for utilities and pipe and cable locating, they got one. Universal colour coding for site surveying, spot and line marking have become the Australian standard, providing a fool-proof method to avoid damaging unseen utilities.

Spot Marking Vs Line Marking

What's the difference? Line marking is your permanent markings used for car parks and roads. Spot paint however is applied mostly by hand or with an applicator gun specifically designed for upside down use. The formulation of spot paint works a treat on a variety of surfaces like dirt, bitumen and even grass, especially if high quality.

Before starting any job involving excavating in an unknown area, check out this best practice guide from Dial Before You Dig. When it comes to locating underground infrastructure, make sure to use the correct colour and note the size of what's below, along with any important measurements that may be relevant to the excavation.

Take a look at the Australian standard paint colours for utilities:

Here’s a deeper look at what some of the colours mean

Orange is the colour for electrical equipment. Orange can indicate the subterranean presence of power lines, cables, conduits, transformers, or even lightning cables.

Yellow is the identifier for natural gas, petroleum, or steam. It’s the colour for urgency and caution. Anyone who’s tapped into a gas line and lived to tell the tale knows the value of accurate markings for gas lines. Oil and steam can be almost as problematic.

White indicates communications. This could include cable TV, phone systems, alarm wiring, fibre optics, or conduits intended to carry signals rather than power. With our modern reliance on telecommunications, it’s wise to be careful when digging around orange markings.

Green, Purple and Blue all indicate water of different types and varieties. it is commonplace for recycled water, potable water, and stormwater all to have separate underground infrastructure. Identifying and avoiding these during excavation is crucial.

Multi- coloured markings are generally found in more suburban areas, where there is a high density of underground utilities and therefore a greater importance for clarity among excavators. No one wants to damage the wrong pipe or cable, like this bloke did...

Spot Marking Symbols

While colours alone specify what exactly lies below the surface, they are not the only part of the equation. Symbols are an essential part in helping identify widths, depths, locations and basically anything to help 'paint' a picture for anyone wanting to excavate.

Symbols let the locator contractor, excavation operator, surveyor and everyone in-between have a clear picture of what's below the ground. Basically, there are four classes. QL-(A) sighted, QL-(B) traced, QL-(C) aligned from surface features, QL-(D) any other method.

Thanks to organisations like Dial before you Dig and the National Utility Locating Contractors Association (NULCA), we have a standard that is truly Australian, without any replication of standards used by the United States.

So next time you spot these weird little markings, see if you can figure out what they mean. Definitely do not use your new-found knowledge of spot paint markings to pick up the local bartender - but at least it’s something to think about…