Locating underground stormwater pipes

Underground stormwater pipes can be hard to find. They can be as shallow as 100mm or many meters deep. They can be made of clay, concrete, cement plastic and metal. If you have a blockage, water damage or rising damp you will need to find your buried storm water pipes. If you want to undertake a renovation, landscaping or excavations, you will need to know where the underground stormwater pipes are so that you do not damage them. You may just want to know what condition they are in.

Dial Before You Dig plans generally do not show the location of government or privately owned stormwater drains. Seek advice from your local council or planning authority before undertaking mechanical excavations.

Some councils require work as executed storm water drainage plans be submitted for approval and future records once a private stormwater drain has been laid and tested. These plans can be very accurate and will provide a good indication of the location the stormwater drains for domestic and commercial buildings. Contact your council or planning authority to see if they have a record of the storm water pipe installation and plans.

I have been in this industry since 1985. It is very rare that you will find marker tape indicating that there is a buried storm water pipe below. If you come across marker tape while excavating with a backhoe or excavated stop work immediately. Marker tape generally indicates that you are directly above a critical underground service. You must either move your excavation, expose the underground service by shovel, or use the hydrovac method to safely excavate the buried services.

Underground metal stormwater pipes are rare, but they can be the easiest to find. They are generally 100mm diameter pipes, are made from steel or cast iron, running from the kerb to the boundary of the property. Metallic pipes are conductive. Therefore, a metal detector may be all that you need, if you are an experienced operator.

We prefer to induce an electronic signal into the metallic pipe and then use a locating device with an inbuilt receiver to find that signal. This method is very accurate and allows us to determine the depth of the underground steel and cast iron storm water pipe. We can also use a CCTV drain camera with a locating sonde attached.

We use a receiver to locate the signal transmitted from the sonde back to the ground. This practice is very precise and provides a lot of information about the internal condition of the pipe.

Underground clay storm water pipes are usually used for older storm water mains and private storm water drainage systems. The diameter is 100mm and larger. This allows access for a CCTV drain camera with a sonde attached. We use a locating receiver to locate the signal transmitted back from the sonde to the ground. This practice is extremely accurate and provides a lot of information about the internal condition of the clay storm water pipes. It is the best method for finding the exact location of blockages, cracks and collapsed pipes.

Underground plastic storm water pipes are usually used for storm water mains and private storm water systems. The diameter of buried storm water pipes is 90 mm and larger. This can allow access for a CCTV drain camera with a locating sonde attached, if the 90mm pipe has no 90 degree bends or straight Ts. We use a locating receiver to locate the signal transmitted back to the ground from the sonde. This method is extremely accurate and provides a lot of information about the internal condition of the buried pipes. This practice is suitable for finding the exact location of blockages and breaks.

Underground cement and concrete storm water pipes can be hard to locate. Generally, the joints, changes of direction and junctions will be poorly formed. Rigid joints that allow roots and soil to enter will be closer together. Storm water drains may be as shallow as 100mm. Therefore, spiking the ground until you find a hard spot that is in a consistently straight line at a consistent depth may be an indication that you are on top of the storm water pipe. CCTV drain cameras can be used. However, we are hesitant to put them in buried cement and concrete storm water pipes, as they can easily become stuck or broken.

Occasionally buried storm water pipes will become so badly blocked that they cannot be cleared and a drain camera cannot be inserted into them and the water jetter or eel cable and cutter will not pass through the blockage. If we can get the eel cable and cutter all of the way to the blockage, we will induce an electronic signal into the metallic eel cable. We then use a locator with inbuilt receiver to locate the signal being emitted from the eel cable inside the storm water pipe.