BLDG1009 Environmental Building Design

The installation of rainwater tank systems in Australia needs to fulfil some regulatory requirements. In Victoria, there are set criteria for a 6-star standard: the requirement is to have a roof catchment area of at least 50 m² with a minimum tank capacity of 2,000 L (5,000 L for a class 1 building), attached to the toilets in the building (Sharma and Gardner, 2020). For this property, a Bushman Tanks TSL1100 model was selected — a 5,000 L polythene tank priced at approximately $2,100–$2,500 (Bushman Tanks, 2023).

Working Principle: Rainwater from the roof is channelled into downspouts and gutters, from where it is filtered with a leaf filter and first-flush diverter before entering the rainwater tank. It is then held until required for domestic usage or garden irrigation; an underwater pump is turned on to distribute collected water to specified locations, like yards, restrooms and laundry machines (Şahin and Manioğlu, 2019).

Rainwater tank systems provide the advantage of minimising water use in bathrooms, laundry and gardens. The water collected is near the source, lowering site run-offs. However, rainwater tanks are only beneficial when used regularly, which frees up the capacity to collect additional water every time it rains (Rainwater Tanks – Melbourne Water, 2023).

The environmental impact of installing a rainwater tank system includes lessening the need for mains water supply, as in Australia, shortage of water is a persistent problem (Tapsuwan, Cook and Moglia, 2018). It decreases the runoff of stormwater, which may release contaminants into neighbouring waterbodies, like the Georges River, by collecting rainfall from the roof. It can reduce energy needs for water purification and distribution by decreasing reliance on mains water. This would improve energy efficiency, lessening domestic carbon emissions and supporting the garden to be more resilient (Conticelli, Proli and Tondelli, 2017). Offering plants with a steady supply of non-toxic water reduces soil erosion and restores groundwater.

At the consumer level, the system lessens reliance on mains supply, reduces water bills and increases the value of the property. Depending on the capacity of the storage tank, the type of materials utilised and the nature of the plumbing, the cost of installation may vary (Yingsamphancharoen and Piriyakul, 2022). In the current case, the entire cost of installation may range between $3,000–$3,500, which may reduce water consumption by up to 30%, approximately.

Based on an initial cost of $3,000–$3,500 and an estimated annual saving of approximately $230, the payback period works out to roughly 13 to 15.2 years — meaning the investment would be recovered through reduced water bills within that timeframe.

Setting up a rainwater system within a house can have significant social effects, such as raising residents' awareness regarding the need for preserving water and serving as a role model to neighbours by embracing sustainable practices (Campisano, D'Amico and Modica, 2017). These systems lessen the strain on the community's water supply, and their widespread use might strengthen community resistance to floods and shortages of water in Southwestern Sydney, which is facing a water shortage problem. Research by Stec and Zeleňáková (2019) found that environmentally friendly amenities, like rainwater collection systems, can boost home prices by up to 10%. Also, rainwater harvesting systems encourage independence and readiness by offering a reliable source of water.