Many Sydney lots have a sewer main, a stormwater pipe or a drainage easement running through them, and that can decide where a new house, extension, granny flat or pool can go. Sydney Water requires its written approval, through a building plan approval in Sydney Water Tap in, before you build over or next to its assets. Its policy says it will not allow building over pressure mains, over gravity sewer mains of 750 millimetres diameter or more, or over its stormwater assets in most circumstances. Council-owned stormwater pipes and drainage easements are controlled separately by the council’s engineering policies and by the terms of the easement on title. The usual answer is to keep buildings clear of the pipe and its easement, and to use pier footings taken below the pipe’s zone of influence where a structure must sit nearby.
Key takeaways
- Sydney Water must approve building plans before building, excavating or landscaping that could affect its pipes; a council DA will generally not be consented without approved plans.
- Sydney Water will not allow building over pressure mains, gravity sewer mains of 750 mm nominal diameter or more, or critical assets, and in most circumstances will not allow building over its stormwater assets.
- Where building over or adjacent is allowed, plans must be certified that the building is outside any Sydney Water easement, clear of the asset and independently structurally supported if the asset fails.
- For Sydney Water stormwater assets within the property or within 10 metres of it, approval is required, and Sydney Water will consider a rebuild over an asset only where an existing dwelling is already over it and there is no feasible alternative.
- Council stormwater pipes and drainage easements follow council policies and the easement terms; typical requirements are clearance from the pipe, pier footings below the zone of influence and no structures within the easement.
Who this is for: home owners and buyers in Sydney, the Illawarra and other Sydney Water areas with a sewer or stormwater line through the block, planning a knock-down rebuild, extension, granny flat, pool or duplex.
How do you find out what pipes are on your land?
Start with three documents: the title and its section 88B instrument (for registered easements), a sewer service diagram from Sydney Water, and a Before You Dig Australia enquiry for other services. A detail survey should then locate the visible features, such as maintenance holes and pits, so the designer can draw the pipe line, depth and any easement on the site plan. Council stormwater pipes often run through rear yards in older suburbs without a registered easement, so ask the council for its stormwater asset information as well.
The common mistake is designing first and checking pipes later. A granny flat positioned over a sewer main can be the difference between an approval and a redesign.
What does Sydney Water allow?
Sydney Water’s policy on building over or adjacent to its assets (April 2021) says you must have its written approval to build over or adjacent to its assets before you start, and it will not allow you to build:
- over pressure mains for water or wastewater, including pressure and vacuum sewer lines and stormwater pressure mains;
- over gravity sewer mains with nominal diameters of 750 millimetres or more, or other critical assets such as tunnels and heritage-listed assets;
- over stormwater assets;
- adjacent to its easement unless you meet the requirements of its technical specification.
Plans must be certified by a suitably qualified person that the building is outside any easement in favour of, or land owned by, Sydney Water; clear of the asset according to its requirements; and independently structurally supported, so the building stays supported if the asset fails. The policy also says the owner bears the costs of investigation, design, protection and any damage, unless otherwise agreed.
Sydney Water recognises that many properties already have buildings over or immediately next to its assets. It will work with owners towards rebuilding in those situations where, among other things, there is an existing council-approved structure over or adjacent to the asset, relocating the asset is not feasible, and the rebuild is like-for-like (for example, single dwelling to single dwelling).
What about stormwater pipes and channels?
Sydney Water’s separate stormwater policy applies where a Sydney Water stormwater asset is within your property or within 10 metres of it. In most circumstances it will allow building adjacent to a stormwater asset but not over it, and any cantilever over the asset is treated as building over. It will consider a rebuild over a stormwater asset only where an existing dwelling is already over it, relocating the asset is not feasible and building over it is the only way to make reasonable use of the land, which the policy defines as a minimum fair-shaped building envelope of 200 square metres for a single dwelling. Buildings should also not obstruct overland flow paths.
Many stormwater pipes on private land belong to the council, not Sydney Water. Councils set their own requirements in engineering policies and DCPs, and they vary. Common themes, illustrated by NSW council policies such as Wagga Wagga’s guidance on building near sewer and stormwater lines, are a clear strip for access along the pipe, no permanent structures over the pipe, footings taken below the zone of influence (an imaginary line drawn up from the base of the pipe trench), and a preference for easily removable structures where anything must be close.
How does this affect your design?
| Situation | Typical approach |
|---|---|
| Sewer main (under 750 mm) crossing the rear yard, no easement | Building plan approval; keep walls clear where possible; piers below the zone of influence for nearby footings; protect maintenance holes and keep them accessible |
| Sewer main crossing where the house must go | Ask whether the main can be deviated at your cost through a water servicing coordinator; otherwise redesign |
| Registered drainage easement in favour of council or a neighbour | No structures within the easement; check its terms in the 88B instrument |
| Sydney Water stormwater channel at the rear | Build adjacent, not over; overland flow and flood levels assessed |
| Pool near any main | Building plan approval; pool shell clear of the zone of influence or engineered accordingly |
The order we suggest
- Obtain the title, 88B instrument, sewer service diagram and council stormwater information before design.
- Have the surveyor locate pits, maintenance holes and, where possible, pipe depths.
- Draw the pipe, its easement and its zone of influence on the site plan.
- Position the building, pool and retaining walls to stay clear, or confirm the engineering solution.
- Lodge plans through Sydney Water Tap in; if there is an impact on the asset, a water servicing coordinator will assess.
- Include the building plan approval with the DA or CDC, and the engineer’s certification with the construction certificate.
Definitions
- Building plan approval
- Sydney Water’s approval of building plans, through Tap in, confirming the work will not damage or limit access to its assets.
- Zone of influence
- The area of ground around a pipe, defined by a line projected up from the base of the trench, within which footings could load or disturb the pipe.
- Drainage easement
- A registered right over land for the passage of stormwater, usually shown on title and in a section 88B instrument, with terms restricting structures.
- Water servicing coordinator
- A Sydney Water accredited provider who manages assessments, protection works and asset adjustments for developers.
- Pier footing
- A footing taken down to firm material below the zone of influence so the building does not load the pipe.
Frequently asked questions
Can I build over a sewer pipe in Sydney?
Sometimes, with Sydney Water’s written approval and certified engineering, but not over pressure mains, gravity mains of 750 mm diameter or more, or critical assets. Keeping clear of the pipe is usually simpler and cheaper.
Do I need Sydney Water approval for a granny flat or pool?
You need to lodge plans through Sydney Water Tap in. If there is no impact on its assets, approval can be immediate; if there is, a water servicing coordinator assesses the plans.
Can I build over a council stormwater easement?
Generally not. Easement terms and council policies usually prohibit structures within drainage easements, and nearby footings must be designed so they do not load the pipe.
Who pays to move a sewer main?
The owner, unless Sydney Water agrees otherwise in writing. Deviations are managed through a water servicing coordinator and can add significant cost and time.
We map pipes, easements and zones of influence at the start of our development due diligence reports and site planning for granny flats and duplexes, so the design avoids them from the first sketch. For the engineering, our sister company Contrive Consultants designs footings and stormwater. To get started, request a fee proposal.
Sources and references
- Sydney Water, Policy: Building over or adjacent to Sydney Water assets (April 2021), accessed October 2026
- Sydney Water, Policy: Building over or adjacent to our stormwater assets (November 2020), accessed October 2026
- Sydney Water, Building plan approvals, accessed October 2026
- Sydney Water, Building over or next to our assets, accessed October 2026
- Wagga Wagga City Council, Building near a sewer or stormwater line, accessed October 2026
Information disclaimer. This article is general planning information prepared by the URBA Planning Team and is current at the date of publication. It is not planning, legal or financial advice for any specific property. Planning instruments, development control plans, state policies and the National Construction Code are amended regularly and councils interpret them differently; the controls quoted here should be confirmed against the versions in force at the date of lodgement and against the consent authority’s current requirements. Reliance on this article is at the reader’s own risk. URBA Planning, a division of Contrive Consultants Pty Ltd, accepts no liability for loss arising from its use. For advice on a specific site, contact URBA for a fee proposal.