How to Find Underground Pipes Before You Dig

A new fence post, retaining wall or trench can turn into an expensive repair quickly when it hits a hidden water, sewer, stormwater or gas line. Knowing how to find underground pipes before any digging starts protects your property, avoids service interruptions and, in the case of gas or electrical assets, helps keep everyone on site safe.

On older homes, rural blocks and properties that have been renovated over time, pipe locations are not always obvious. Plans may be incomplete, pipes may have been rerouted, and their depth can vary considerably. Treat every proposed excavation as a job that needs checking first - even if you are only digging a shallow hole.

Start by checking plans and visible clues

The first step is to gather as much information as possible before reaching for a shovel or hiring a machine. If you have building plans, drainage plans, renovation paperwork or photographs from previous works, review them carefully. They can provide a useful starting point, but they should not be treated as proof of an exact pipe location or depth.

Look around the property for visible clues. Water meters, gas meters, sewer inspection openings, grated drains, downpipes, pump systems, hot water units and rainwater tanks can all indicate where underground services may run. A water pipe will usually travel from the meter towards the home, while gas pipework commonly runs from the gas meter to appliances such as the hot water system, cooktop or heater.

For drainage, check the direction of downpipes, surface grates and existing inspection points. Stormwater pipes often run from roof downpipes to soakwells, drains or lawful discharge points. Sewer pipes generally follow a route from toilets, bathrooms and kitchens towards the connection point, but extensions and past alterations can make the route less direct than expected.

On rural properties, also consider water tanks, bores, irrigation lines, sheds, stock troughs, septic systems and effluent disposal areas. These services may be spread across a larger area and may not appear on standard house plans.

Contact utility providers before excavation

Before digging near a boundary, verge, driveway or service connection, request available underground asset information through Before You Dig Australia and check with relevant utility providers. This process can identify public utility assets such as electricity, gas, telecommunications and water infrastructure in or near the work area.

However, plans supplied by utilities have limits. They may show the general alignment of an asset rather than its exact position, and they usually do not identify privately owned pipes after the connection point. For example, the water service from the meter to your house, private stormwater pipes, garden irrigation and drainage installed by a previous owner may all sit outside the information provided.

Use plans to assess risk and plan the job, not as a green light to excavate without further checks. If a marked service is near your proposed work, arrange professional locating and use careful non-mechanical excavation where required.

How to find underground pipes with practical checks

For a simple project away from known services, a few careful checks can help narrow down likely pipe routes. Start at the known connection point and trace the most logical path to the fixture or outlet it serves. A line from the water meter to the house, for instance, is often reasonably direct, but landscaping, driveways and renovations can change that route.

You can gently probe loose soil by hand in low-risk areas, but do not force a metal bar or sharp tool into the ground. This can damage plastic pipework, insulation, cable sheathing or older earthenware drains. Hand digging is safer than machine digging near suspected services, although it still needs to be done carefully.

Never rely on assumptions such as “the pipe will be deep enough” or “it should run in a straight line”. There is no single standard depth for private pipework. Soil movement, previous landscaping, tree roots, repairs and building work can leave services shallow, offset or poorly protected.

Avoid using water pressure, dye or excavation as a first method for finding a suspected damaged line. These approaches can create mess, worsen leaks and cause unnecessary disruption. When the pipe route matters to a building project or repair, purpose-built locating equipment is the more reliable option.

Professional methods for locating hidden pipework

A licensed plumbing professional can choose the locating method that suits the type of pipe, the site conditions and the reason it needs to be found. One tool does not locate every pipe, particularly on properties with a mix of old and new plumbing.

CCTV drain camera inspections

For sewer and stormwater pipes, a CCTV drain camera is often the most useful starting point. The camera travels through the pipe from an accessible opening and shows its condition from the inside. It can reveal cracks, tree root intrusion, crushed sections, poor connections, blockages and changes in pipe material.

When used with a locating transmitter, or sonde, the camera location can be traced from above ground. This allows the plumber to mark the pipe route and identify the position of a blockage or damaged section before excavation. It is particularly helpful when a drain is buried beneath paving, lawns, driveways or landscaped areas.

Electronic pipe locating

Electronic locating equipment can trace many metal pipes and cables. It may also locate non-metallic pipework when a tracer wire has been installed alongside it, or when a sonde is placed inside the line. This is commonly used to identify the route of water, gas, sewer and stormwater services where access points are available.

The result is influenced by pipe material, depth, nearby services and ground conditions. A locator can provide a strong indication of alignment, but careful verification is still needed before digging. Marked locations should be treated as a guide with an allowance either side, rather than a precise line to excavate against.

Ground-penetrating radar and other specialist options

Ground-penetrating radar may assist where there are multiple unknown services or no accessible pipe opening. It can be useful for certain sites, but it is not a guaranteed solution. Wet ground, clay, reinforcing steel, dense services and some soil types can reduce its effectiveness.

Leak detection equipment is different again. Acoustic listening devices, thermal methods and pressure testing can help find a concealed water leak, but they are not always designed to map the full route of an undamaged pipe. A good diagnosis starts with the question you need answered: are you trying to avoid a pipe during excavation, locate a blockage, or find a leak?

Take extra care around gas, sewer and electrical services

Gas pipework should never be exposed, altered or repaired by an unlicensed person. If you smell gas, hear hissing near a gas line, or suspect excavation has damaged a gas service, stop work immediately. Keep ignition sources away, move people clear of the area and contact the relevant emergency service or a licensed gas fitter.

Sewer and drainage pipes carry their own risks. A cracked sewer line can contaminate soil and lead to ongoing odours, blockages or subsidence. Damaging a stormwater pipe may not be obvious straight away, but it can later cause water pooling, erosion or foundation moisture issues.

Electrical and telecommunications services may share similar corridors with plumbing. Do not assume a trench contains only one pipe. This is one reason professional service locating is a sensible investment before machine excavation, retaining wall construction, pool installation or major landscaping.

When to call a plumber to locate pipes

Professional help is worthwhile whenever the cost of getting it wrong is higher than the cost of locating the service. That includes digging near a house, installing a shed, replacing a driveway, building a fence close to service routes, investigating recurring drain blockages or planning a renovation.

It is also the right call when the property has unexplained wet patches, low water pressure, sewer smells, overflowing drains or unusually high water use. Those signs may point to a hidden leak or damaged underground pipe, and locating the issue accurately can reduce unnecessary excavation.

For Busselton and South West property owners, SmartFlow Plumbing & Gas can use practical inspection and drain camera methods to help identify hidden drainage issues and plan repairs with less disruption. The best approach depends on the pipe material, access points and what is happening on site.

Marking a likely route before work begins is a small step that can prevent a damaged service, a disrupted project and a much larger bill. If there is any doubt about what is below ground, pause the job and have the area checked before digging.