Performance of Rainwater Tanks in Carrington NSW

This report analyses the benefits of the combined installation of rainwater tanks and water efficient washing machines. The water sensitive devices are installed in a small inner city home and demonstrate the ability to produce optimal water saving solutions regardless of size or location of the home.

A manual monitoring program suggests a 62% reduction in demand for mains water and the total value of benefits were estimated to be $3.24/kL following the dual water supply scheme. The study also details the treatment train effect of rainwater to highlight improved quality of rainwater supply. The site remains as an ongoing quality research facility. Design and installation of the scheme is presented

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Performance of Rainwater Tanks in Australian Capital Cities

This report examines the performance of rainwater tanks of sizes 1kL to 10kL for four major Australian cities; Sydney, Brisbane, Melbourne and Adelaide. A number of academically established models are used to simulate the performance of rainwater tanks with seasonally uniform rainfall.

For each city, research suggests that the use of rainwater tanks results in considerable reduction in mains water consumption. Locations typical of greater annual rainfall yielded better outcomes, such as Brisbane and Sydney. Mains water savings increased with larger tank and roof sizes whilst rainwater tanks also reduced storm water peak and volumetric discharges from roof areas.

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Rainwater Tank Options for Storm Water Management in the Upper Parramatta River Catchment

The study investigates the extent to which rainwater tanks reduce the amount of on site storm water detention (OSD) to satisfy the Upper Parramatta River Catchment Trust’s policies. Use of 10 kL tanks with 0 and 5 kL detention storage were examined. Installation of rainwater tanks for single dwellings and townhouses were shown to contribute significantly towards the allotments OSD volume. Rainwater tanks are also expected to reduce mains water consumption by up to 39% where variation depends on the allotment occupancy, tank airspace for detention and the fraction of allotment drained by rainwater tanks.

Conventional design storm approach, recommended by Australian Rainfall and Runoff, is intrinsically incapable of performing the assessment in this case study. To give a continuous simulation approach, the DRIP stochastic rainfall model was adopted and shown to be the only feasible and rigorous method.

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Rainwater Tanks in Inner City: Economic, Water Quantity and Quality Impacts

This case study investigates the effects of installing a dual water supply system in Maryville, an inner city suburb of Newcastle. The dual water supply system utilizes rainwater as a supply source in addition with conventional mains water. The design, construction, costs and performance of the dual system water supply system are examined in this paper.

Monitoring of water quality reveals the rainwater supply to be compliant with Australian standards for hot water, toilet and outdoor use. Rainwater from the hot water service was also compliant with national drinking standards. Reports find the costs of rainwater supply to be significantly less than the price of mains water typical to the Lower Hunter region. Further analysis into the entire urban water cycle following the introduction of rainwater tanks may reveal considerable community benefit.

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Economic Benefits of Rainwater Tanks: An Investment Model

This paper presents a community based investment model to investigate the economic benefits derived from installation of rainwater tanks. The model produces comparisons between a base scenario of traditional urban water design and alternative scenarios which incorporate rainwater tanks.

The study finds the magnitude of economic benefit from widespread rainwater tank installation to be dependent on real interest rates, savings from reduced mains water demand and installation costs of rainwater tanks. Despite this, modeling suggests rainwater tanks provide greater economic benefit than traditional water supply and storm water management options. The paper presents compelling conviction in widespread installation of rainwater tanks.

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Cost Effectiveness of Rainwater Tanks in Urban Australia

The report investigates the cost benefits associated with rainwater tanks from the perspective of the Australian home owner. The use of water tanks in urban areas has recently increased following the introduction of local Government policies to encourage their use.

The investigation analyses typical household water demand with expected yield from rainwater tanks and associated costs of implementing a rainwater tank. Research indicates that the installation of larger tanks have higher likelihood of yielding a cost benefit to home owners.

This paper is part of a series of works commissioned by the National Water Commission on key water issues.

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