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Locating services: Before You Dig, sewer, water, power, gas and existing retic

In WA you have a legal obligation under the Work Health and Safety Act 2020 to identify underground services before excavating, and you can be held liable for the damage. The free lodgement takes a day; hitting a gas main takes considerably longer.

⏱ 45 minIntermediate🔗 9 resources (8 free)

There is a particular sound a 5-tonne excavator makes when the bucket finds a sewer, and everyone on site knows what it was before the operator has finished the swing. The gas main version is quieter and much worse.

On a renovation this risk is higher than on a new block, not lower. A bare subdivision lot has services installed to a recent standard with an as-built plan that reflects it. A 1970s house in Morley has forty years of undocumented private work under the lawn: a retic mainline someone ran in 1988, a bore power cable at spade depth, a pool pump feed, a decommissioned septic tank, and a sewer junction nowhere near where you would put it. This lesson gets all of it onto your base plan before you draw a line you might have to erase.

What a professional does at this stage

A competent landscape contractor treats service location as a document trail, not a hunch. Before quoting they will have lodged a Before You Dig Australia enquiry, read the plan pack from every responding asset owner, walked the site looking for surface evidence, and priced potholing into the job. If the design touches a sewer they raise it at concept stage, not during excavation.

The reason is partly legal. Under the Work Health and Safety Act 2020 (WA) and the Work Health and Safety (General) Regulations 2022, regulation 304 covers “Excavation work: underground essential services information”, and it sits in the part of the regulations that imposes duties on a person conducting a business or undertaking. In plain terms: the moment you engage a landscaper, a bobcat operator or a plumber, that duty is live on your site — and you are the one holding the site knowledge they need. If you are digging alone on your own house, whether the WHS duty bites is arguable. Whether you pay for the repair is not.

The rest is commercial. Moving a retaining wall 600 mm on paper costs nothing. Moving it after the footing is poured costs the footing.

Lodging the BYDA enquiry

Do this first, because it is free and it takes ten minutes. Register at byda.com.au, draw your dig area on the map, and lodge. Every asset owner with registered infrastructure near that polygon is notified and each replies to you directly.

Plans usually arrive within minutes, but allow up to two business days — lodge before the weekend, not the morning you hire the mini-ex. Note that BYDA itself sends you nothing; the plans come from Water Corporation, Western Power, ATCO Gas and the comms carriers, so you will get several emails with different formats and different conditions attached.

What the plans will not tell you

Three limitations matter more than anything the plans do say.

Limitation What it means on your block
Plans are indicative only The line on the page is a schematic, not a survey. Treat it as “somewhere near here”.
Coverage generally stops at the boundary Mains and lead-ins are shown. What runs across your back lawn often is not.
Depth is never guaranteed Sand moves, levels get changed, kerbs get rebuilt. Never assume a cable is deep.

That third one is a Perth specific. Our sand is easy to trench, and it is just as easy to strip 200 mm off a lawn during a renovation without anyone recording it. A cable buried to spec in 1985 may be 150 mm down today.

The sewer, and why you cannot build over it

Most Perth blocks have a gravity sewer running from the house to a main, and on many older lots that main crosses private property. Water Corporation names sewer reticulation pipes of 300 mm and smaller as the most common asset found inside private property.

You need approval before building a house, shed, garage, carport, pool, spa or retaining wall near one, and the clearance depends on how deep the sewer is and what it is made of. There is a stricter set of distances for conventional footings and a closer set if you pile past the pipe’s zone of influence — but piling means a structural engineer, drawings and cost, which is usually the moment a client decides the pergola can move two metres.

Walk the block and look for:

  • Access chambers — a round or square cover, often cast into a path or lost under mulch. It must stay accessible and at finished level, so it constrains your paving levels as well as your plan.
  • The inspection opening near the house, usually a capped riser at ground level close to the wet areas.
  • A straight line of settlement or greener grass between the two.

If the block is old enough to predate infill sewerage, or is semi-rural, it may still be on a septic tank and leach drains. Those cannot be paved or built over either, and they are rarely on any plan. Ask the previous owner and look for the tank lids.

Power, gas, comms and the bore

Power. Western Power requires you to know the location and voltage of any underground cable before working near it, and points you to BYDA or freecall 1100 for that information. If you expose a cable that is not on your plans, or find damaged insulation, stop and ring 13 10 87. Look up as well as down — overhead consumer mains from the pole to the house are a real constraint on where a tall tree or a pergola can go.

Gas. Perth metro reticulated gas is ATCO. Gas services are commonly shallow, and a nicked polyethylene service is an evacuation, not an inconvenience. Hand dig near anything the gas plan shows.

Comms. NBN and Telstra pits are usually in the verge, which matters because verge landscaping and driveway crossovers sit right on top of them.

The bore. The WA one nobody warns you about. If the property has a garden bore, a power cable runs from the meter box to the pump at whatever depth the person who installed it felt like, and it will not be on any BYDA plan because it is a private asset. Find the pump, find the meter box, and assume the cable takes the shortest ugly route between them until you have proved otherwise.

Your existing retic

No asset owner has a plan for this, so you make one. Run each station from the controller and watch where the heads pop — that gives you zones and rough alignments. Solenoid valves are the hard part; they get buried and mulched over. A wire and valve locator, hireable by the day from most Perth irrigation shops, traces the control wire from the controller straight to the solenoid.

Mark everything with pegs and spray paint, photograph it against fixed reference points from your measuring-up survey, and get it onto the base plan the same day. The irrigation lessons in Phase 8 assume you know what is already in the ground.

Pothole before you commit

Plans get you close; only exposing the service tells you where it is. Hand dig or soft-dig at every point where your design crosses a located service — footings, soakwells, tree pits, mainline trenches. In Perth sand this is quick, which removes the usual excuse. Record the depth and the offset from a fixed point. Those two numbers turn “there is a sewer somewhere around here” into a line you can design to.

What this changes downstream

Your services plan becomes a constraint layer that sits under everything in Phase 5 and Phase 6 — where the pool can go, where the retaining wall footing lands, where the deep-rooted tree does not go, and where the drainage falls.

The next lesson audits what is already growing and already built on the block, assessing the existing garden, and it uses this plan to decide what can be kept, what must move and what is sitting on top of something you cannot disturb.

Do this on your own block

Field journal entry

Services plan

Lodge a Before You Dig Australia enquiry for your address, then mark every located service on your base plan: sewer line and access chambers, water main and meter, power (overhead and underground), gas, comms, and every existing retic line and valve you can find.

Sign in to write this straight into your project workbook — or just keep it in a notebook.

Checklist

  • Lodge a free Before You Dig Australia enquiry at least one business day ahead
  • Locate the sewer line and any access chamber — you cannot build over it
  • Find the water meter, the isolating valve and any bore
  • Trace and mark existing reticulation before you dig anything

Watch

The 5 Ps of Safe Excavation. Before You Dig Australia (BYDA)

Before You Dig Australia🇦🇺 Australian

The official animation of the Plan, Prepare, Pothole, Protect, Proceed sequence, straight from the service that runs the referral system. Watch it once so the vocabulary in the asset owners' plan packs makes sense when they land in your inbox.

Locating Irrigation Wires and Valves with a Wire/Valve Locator

Hunter Landscape Irrigation🌏 Works anywhere

The manufacturer demonstration of how a wire and valve locator is actually set up and swept, which is the only reliable way to find solenoid valves someone buried and mulched over years ago. Directly relevant because existing retic is the one service on your block that no asset owner has a plan for.

Change this for Perth

Hunter is one of several brands sold in Perth alongside Toro, Rain Bird and K-Rain, and the technique is identical regardless of whose valves are in the ground. Most Perth irrigation shops hire a locator by the day rather than making you buy one.

Where to go deeper

Every link below was fetched and checked before it shipped. Nothing here is a guess.

  • Freegovernment15 min to read, 10 min to lodgeAustralian

    Before You Dig Australia — for homeowners

    Before You Dig Australia (BYDA)

    Why this oneThe homeowner-facing page of the national referral service, and the one that says plainly what the plans are and are not. It states that the plans are indicative only, that they may show lead-ins to the property or mains at the boundary but may not contain specific details inside your property boundary, and that you should never assume the depth of a pipe or cable. Read this before you lodge, not after the plans arrive and confuse you.

    Change this for Perth

    BYDA is national. In Perth the responding asset owners are typically Water Corporation, Western Power, ATCO Gas and the comms carriers, and each replies separately with its own plan set and its own conditions — so expect several emails, not one document.

    Link checked 2 Aug 2026

  • Freetool10 minAustralian

    BYDA guide to free plans

    Before You Dig Australia (BYDA)

    Why this oneThe practical how-to for the lodgement itself, including the point most people miss: the plans do not come from BYDA, they come from each asset owner, and while they typically arrive within minutes you should allow up to two business days. It also states that if your scope of works changes or the plan validity dates expire you must lodge again — relevant if your renovation stretches across months.

    Link checked 2 Aug 2026

  • FreestandardAustralian

    BYDA best practice guides — the 5 Ps of safe excavation

    Before You Dig Australia (BYDA)

    Why this oneFree downloadable guides covering the Plan, Prepare, Pothole, Protect, Proceed sequence that the whole industry works to, plus asset location methods, potholing by hand digging or hydro vacuum extraction, and how to protect infrastructure once it is exposed. This is the closest thing to a free written standard for the job, and it is what a competent contractor is following whether or not they can name it.

    Link checked 2 Aug 2026

  • Freegovernment10 minPerth / WA

    Locating our assets

    Water Corporation

    Why this oneWater Corporation's own method for finding its water, sewer and drainage pipes, and it is refreshingly blunt: BYDA plans give you approximate location only, and potholing by careful hand digging or soft-dig vacuum excavation is the only way of determining pipeline location with certainty. It also flags that electronic detection works on metallic and reinforced concrete assets but not on non-metallic pipe, which is exactly the trap on a Perth block full of PVC.

    Link checked 2 Aug 2026

  • Freegovernment15 minPerth / WA

    Building on a residential property

    Water Corporation

    Why this oneThe page that decides whether your pergola, shed, pool or retaining wall is legal where you drew it. It requires you to locate Water Corporation assets before submitting a building application, and sets out clearance distances that vary with the depth and material of the sewer, with a separate, closer set of distances available if you pile the footings. Sewer reticulation pipes of 300 mm diameter and under are named as the most common asset found inside private property — which is most Perth back yards.

    Change this for Perth

    The clearance tables live in the linked Residential guidelines for designers PDF rather than on the page itself, and Water Corporation states it will not advise on structural design — that is your engineer's job. Get the numbers from the current PDF before you finalise any footing near a sewer.

    Link checked 2 Aug 2026

  • FreegovernmentPerth / WA

    Excavation: code of practice

    WorkSafe WA (Department of Energy, Mines, Industry Regulation and Safety)

    Why this oneWA's own approved code of practice for excavation and earthworks, free as a PDF, and the document an inspector would measure a site against. It covers identifying buried services before excavation, providing obtained service plans to the contractor doing the digging, potholing to expose services, and direct supervision whenever underground power, gas, water or sewer is being exposed.

    Change this for Perth

    This code was originally made under the old Occupational Safety and Health Act 1984 and continues in force under transitional arrangements. A replacement Excavation work code of practice was out for public consultation in early 2026, so check the WorkSafe publications page for a newer version before relying on the detail.

    Link checked 2 Aug 2026

  • FreegovernmentPerth / WA

    Work Health and Safety (General) Regulations 2022 (WA)

    Western Australian Legislation (Parliamentary Counsel's Office)

    Why this oneThe primary source, free, in consolidated form. Regulation 304 is titled "Excavation work: underground essential services information" and sits in Part 6.3 Division 3 alongside regulation 305 on managing excavation risks and regulation 306 on additional controls for trenches. If you want to know what the law actually says rather than what a safety blog says it says, download the current consolidation here.

    Change this for Perth

    Written as legislation, not guidance. The duties in Part 6.3 attach to a person conducting a business or undertaking — so they bind the landscaper, excavator operator or plumber you engage, and they bind you if you engage workers, rather than a homeowner digging alone on their own house.

    Link checked 2 Aug 2026

  • Freegovernment10 minPerth / WA

    Excavation — working near our network

    Western Power

    Why this oneShort, and the only thing you need from the network operator before you dig in the Perth metro area. It states that you must know the location and voltage of any underground cable before working near it, directs you to BYDA or freecall 1100 for that information, and gives 13 10 87 as the number to ring if you find damaged insulation or a cable that is not on your plans.

    Change this for Perth

    Western Power covers the South West Interconnected System — Perth, the South West and the Wheatbelt. If your block is outside that, Horizon Power is the operator to contact instead.

    Link checked 2 Aug 2026

  • Paid · $33.90 per title copy (fees effective 1 July 2026)government30 min including deliveryPerth / WA

    Order a Certificate of Title

    Landgate

    Why this oneUnderground pipes are a physical problem; easements are a legal one, and they do not appear on a BYDA plan. Ordering your own title through Landgate's Land Enquiry Services shows the document numbers for every encumbrance and notification registered against your land, including drainage and sewerage easements, and it arrives by email within about 30 minutes.

    Change this for Perth

    The title lists encumbrances by document number; to read what an easement actually restricts you usually have to order the referenced document as well, at the same fee. Free alternative — your settlement pack from when you bought the house almost certainly contains a title search already.

    Link checked 2 Aug 2026

The rules, with sources

WA regulation changes. Each point below names its primary source and the date it was last checked — always confirm with your own council before you build.