Sewer Vent | NSW Environment & Heritage

Culture and heritage


Sewer Vent

Item details

Name of item: Sewer Vent
Other name/s: The Obelisk, Obelisk Sewer Vent
Type of item: Built
Group/Collection: Utilities - Sewerage
Category: Other - Utilities - Sewerage
Location: Lat: -33.8746730209 Long: 151.2098560630
Primary address: Elizabeth Street, Sydney, NSW 2000
Parish: St James
County: Cumberland
Local govt. area: Sydney
Local Aboriginal Land Council: Metropolitan


Within Road Reserve Elizabeth Street. The physical and operational curtilage of the ventshaft is restricted to all the original fabric of the ventshaft and the property upon which it is constructed.
All addresses
Street AddressSuburb/townLGAParishCountyType
Elizabeth StreetSydneySydneySt JamesCumberlandPrimary Address
Bathurst StreetSydneySydney  Alternate Address


Organisation NameOwner CategoryDate Ownership Updated
Sydney WaterState Government 

Statement of significance:

The first planned sewerage system in the city of Sydney was completed in 1857. The Obelisk was the first major sewer vent constructed and the only ventshaft constructed entirely of sandstone. The Obelisk Vent was an ambitious achievement at the time of construction owing to its utilitarian purpose. It is historically significant as one of the oldest items of infrastructure in the early City sewerage system. It has landmark qualities, providing a fitting terminus to the eastern end of Bathurst Street.

It is also significant for its contribution to the streetscape of Elizabeth Street, its visual role in the axial vistas of Sydney, and as a significant object within Hyde Park.
Date significance updated: 30 Nov 01
Note: The State Heritage Inventory provides information about heritage items listed by local and State government agencies. The State Heritage Inventory is continually being updated by local and State agencies as new information becomes available. Read the OEH copyright and disclaimer.


Designer/Maker: Public Works Department
Builder/Maker: Public Works Department
Physical description: A simple masonry shaft consisting of a sandstone base and decorative bronze ventilator apex. The obelisk was built to ventilate Sydney's first planned sewerage system which was constructed by the Municipal Council.Sydney’s first planned sewerage system consisted of 5 harbour outfalls. It was completed in 1857. The only means of ventilating this system was a sandstone ventshaft, which was erected at Hyde Park (corner of Bathurst and Elizabeth St) in 1857. As the sewerage system developed it became obvious that ventilation of the system was inadequate and some form of ventilation was necessary.

In 1875 the Sydney City and Suburban Health Board recommended in its Sixth Progress Report, that two sewerage schemes be constructed to deal with the health problems being faced due to the pollution within Sydney Harbour. From that period several methods of ventilating the sewers were investigated to deal with the disease, odour, pressure and chemical problems being experienced within the sewers.

Of the methods investigated and adopted, including street vents, house vents (cast iron traps and water traps) and flues, the tall ventshafts were determined by Mr. J.M.Smails in several reports to the government of the day, to be the most efficient way of dispersing the pressure and gases found within the sewers.

Initially, after the Obelisk, ventshafts were constructed using bricks, were ornate and fairly major features in the city landscape. This technology was replaced with smaller, steel tube vents, which were used at intervals of approximately every 350m of sewer.
Date condition updated:09 Jan 01
Further information: See inventories for the Main Northern Ocean Outfall Sewer, Lewisham Sewer Ventshaft, Marrickville Sewer Ventshaft, Glebe and Bellevue Hill Sewer Ventshafts for other details relating to sewer vents.
Current use: Monument
Former use: Ventilation of Sewer


Historical notes: There are two types of sewer vents within the Sydney Water system; educt and induct. Induct vents draw air into a sewerage system to areate the pipelines. Educt vents allow gases to escape when the gas is lighter than air. The shape of the cowling on the older types of vents were set to produce either eduction or indcution whenever there is a natural breeze. This is an educt shaft, a simple masonry shaft modelled on Cleopatra's Needle (now situated on the Thames Embankment, London) and erected in 1857 during the period of George Thornton as Mayor of Sydney. Vents are for the safety of personnel as well as to prevent corrosion by chemical decay. The ventilation of sewers is a very important facet of continued operation of a sewerage system. Poor ventilation can result in serious odour problems and breakdown in fabric.

Historic themes

Australian theme (abbrev)New South Wales themeLocal theme
3. Economy-Developing local, regional and national economies Environment - cultural landscape-Activities associated with the interactions between humans, human societies and the shaping of their physical surroundings (none)-
3. Economy-Developing local, regional and national economies Events-Activities and processes that mark the consequences of natural and cultural occurences (none)-
3. Economy-Developing local, regional and national economies Health-Activities associated with preparing and providing medical assistance and/or promoting or maintaining the well being of humans (none)-
3. Economy-Developing local, regional and national economies Technology-Activities and processes associated with the knowledge or use of mechanical arts and applied sciences (none)-
4. Settlement-Building settlements, towns and cities Utilities-Activities associated with the provision of services, especially on a communal basis (none)-

Assessment of significance

SHR Criteria a)
[Historical significance]
The Obelisk was the first sewer ventshaft built to eliminate noxious gases from the sewer at levels that would not be detected by the residents of the city. The ventshaft was built to replace the street gratings that had been used to ventilate the sewer system.
SHR Criteria c)
[Aesthetic significance]
The Obelisk is a sandstone ventshaft which displays the classical architecture and technology of the late nineteenth century. It is a landmark feature within Hyde park and Sydney, which is visible as a major feature at the end of Bathurst Street.
SHR Criteria d)
[Social significance]
It is significant in the development of the ventilation of the sewerage system of Sydney and has been identified by the National Trust Australia (NSW).
SHR Criteria e)
[Research potential]
The design and placement of the Obelisk was used to understand the behaviour of gases within the sewerage system and how to best design vents to help eliminate the gases safely. The ventshaft was also to relieve the gaseous pressure that built up within the sewer system.
SHR Criteria f)
The Obelisk is unique in NSW. It is one of the oldest items of infrastructure in the early city sewerage system. It was the first ventshaft built to eliminate noxious gases from the city's sewer system.
SHR Criteria g)
The Obelisk Sewer Ventshaft is the only example of a sewer ventsahft constructed of sandstone within the Sydney Water system, but is representative of sewer ventilation methods.
Integrity/Intactness: Considerably intact apart from alterations to its base.
Assessment criteria: Items are assessed against the PDF State Heritage Register (SHR) Criteria to determine the level of significance. Refer to the Listings below for the level of statutory protection.

Recommended management:

Manage the place and its significant components in accordance with the Heritage Council State Owned Heritage Asset Management Guidelines and the Minimum Standards of Maintenance and Repair in the NSW Heritage Regulations. Manage significant site elements in accordance with a Conservation Management Plan (CMP). If no CMP exists, consult with Asset Management Commercial Services with respect to commissioning a CMP. When commissioning a CMP, do so in accordance with the Model Brief for CMPs available on ConnectNet. Seek endorsement of the CMP from the Heritage Council of NSW. Works undertaken in accordance with a Heritage Council-endorsed CMP do not require further approval under the NSW Heritage Act. Involve heritage professionals as required under the terms of the CMP, or as otherwise determined necessary. Review CMP every 5 years or in a major change of circumstances, whichever is sooner. Review of a CMP should only be undertaken following consultation with Asset Management Commercial Services . When commissioning a CMP review, do so in accordance with the Model Brief for CMPs available on ConnectNet. Where no CMP is in place, or where works are outside the scope of the existing CMP, assess heritage impacts of proposed works in accordance with Sydney Water Environment Impact Assessment guidelines (e.g. undertake a Heritage Assessment and/or Statement of Heritage Impact as required, obtain Heritage Council approval as required). Consult with the Heritage Manager, Environment and Innovation, when major works are planned which affect items of State heritage significance. Undertake archival and photographic recording before major changes, in accordance with Heritage Council guidelines. Lodge copies of the archival record with the Sydney Water Archives and the NSW Heritage Office. Where the item is listed in a Local Environmental Plan Schedule of Heritage items, determine if works are exempt from approval under the LEP provisions. Where works are not exempt, obtain necessary approvals from the local council, in accordance with SWC EIA Guidelines.

Procedures /Exemptions

Section of actDescriptionTitleCommentsAction date
21(1)(b)Conservation Plan submitted for endorsementThe Obelisk CMP, by Sydney Water for Sydney Water, dated August 2005 CMP endorsed by the Heritage Council on 23 September 2005 for a period of five years, expires 23 September 2010. Sep 23 2005
57(2)Exemption to allow workStandard Exemptions SCHEDULE OF STANDARD EXEMPTIONS
Notice of Order Under Section 57 (2) of the Heritage Act 1977

I, the Minister for Planning, pursuant to subsection 57(2) of the Heritage Act 1977, on the recommendation of the Heritage Council of New South Wales, do by this Order:

1. revoke the Schedule of Exemptions to subsection 57(1) of the Heritage Act made under subsection 57(2) and published in the Government Gazette on 22 February 2008; and

2. grant standard exemptions from subsection 57(1) of the Heritage Act 1977, described in the Schedule attached.

Minister for Planning
Sydney, 11 July 2008

To view the schedule click on the Standard Exemptions for Works Requiring Heritage Council Approval link below.
Sep 5 2008

PDF Standard exemptions for works requiring Heritage Council approval


Heritage ListingListing TitleListing NumberGazette DateGazette NumberGazette Page
Heritage Act - State Heritage Register 0164215 Nov 02 2209711
Heritage Act - s.170 NSW State agency heritage register 285160   
National Trust of Australia register  618625 May 75   
Register of the National Estate 00180121 Mar 78   

Study details

TitleYearNumberAuthorInspected byGuidelines used
Sydney Water Heritage Study1996285160Graham Brooks and Associates Pty LtdGRAHAM BROOKS AND ASSOCIATES PTY LTD 1 JULY 1996 Yes
Alexandra Canal Conservation Management Plan2004 NSW Department of Commenrce, Heritage Design Services  Yes

References, internet links & images

TypeAuthorYearTitleInternet Links
Tourism 2007Obelisk View detail
TourismAttraction Homepage2007Obelisk View detail

Note: internet links may be to web pages, documents or images.

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(Click on thumbnail for full size image and image details)

Data source

The information for this entry comes from the following source:
Name: Heritage Office
Database number: 5053881
File number: H05/00094

Every effort has been made to ensure that information contained in the State Heritage Inventory is correct. If you find any errors or omissions please send your comments to the Database Manager.

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