|Dam and spillways|
|Dam volume||2,376,000 gallons|
The reservoir is rectangular in shape, measuring 180 by 108 feet (55 by 33 m) and is 22 feet (6.7 m) tall. It is divided into two chambers by a 15-foot-6-inch (4.72 m) separating wall which supports a walkway. The reinforced concrete roof and park above are supported by concrete pillars spaced at 12 feet (3.7 m) intervals throughout both chambers.
Access to the reservoir is through the adjoining valve house which extends a further two storeys underground and housed pumping equipment in the lowest level.
Balmain reservoir was built in 1915 by the Metropolitan Board of Water Supply and Sewerage, Sydney, and was originally supplied with water by gravity from Potts Hill. The restoration of Gladstone Park and the erection of a bandstand was made a condition of construction of the reservoir. The facility was made redundant by the commissioning of Petersham Reservoir in 1965 and has remained disused ever since.
Balmain Reservoir Valve House
The neighbouring valve house was constructed in 1917 on the Booth Street frontage of the park and this, together with the footings of the bandstand, can still be seen today. Restoration work on the valve house earned a National Trust of Australia Heritage Award in 2006.
- "BALMAIN.". Construction and Local Government Journal. XII (296). 5 January 1914. p. 12. Retrieved 3 September 2016 – via National Library of Australia.
- "BALMAIN RESERVOIR.". The Sydney Morning Herald (25,037). 4 April 1918. p. 8. Retrieved 3 September 2016 – via National Library of Australia.
- "Balmain Reservoir (Covered) (WS 0006)". Sydney Water. Retrieved 3 September 2016.
- "BALMAIN RESERVOIR". The Sun (698). Sydney. 13 August 1916. p. 11. Retrieved 4 September 2016 – via National Library of Australia.
- "Balmain Reservoir Valve House". Sydney Water. Retrieved 3 September 2016.
- "A BALMAIN CELEBRATION.". The Sydney Morning Herald (25,040). 8 April 1918. p. 8. Retrieved 4 September 2016 – via National Library of Australia.
- "GENERAL NOTES.". The Sydney Morning Herald (23,992). 1 December 1914. p. 12. Retrieved 3 September 2016 – via National Library of Australia.
- Solling, M; Reynolds, P; Leichhardt: On the margins of the city, Allen & Unwin, 1997, ISBN 1-86448-408-X.
- Metropolitan Board of Water Supply and Sewerage; Balmain Service Reservoir, Original site and contract plans; Date Unknown.
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