Part 3 Alternative water sources Part 3 of Best practice guidelines for water conservation in commercial office buildings and shopping centres provides advice on alternative water sources that may be used in commercial buildings. 95 96 3 Chapter 20 – Rainwater 3 Chapter 20 Rainwater Using rainwater is an excellent way to reduce demand on mains drinking water. Rainwater collected from roofs generally has low levels of pollutants, especially if a first flush diverter is installed. This makes any required treatment relatively simple and inexpensive. The bigger and cleaner your roof catchment area, the more likely it is that you will be able to implement an effective rainwater reuse scheme. Using rainwater NSW Health does not as toilet flushing or cooling recommend using rainwater tower makeup. Frequent use of Rainwater can be used to replace for drinking and cooking when rainwater also maintains better drinking water for a range of an alternative mains water water quality. uses including water features, source is available. Guidelines toilet flushing, water heating are available in the document systems, garden irrigation How much rainwater Rainwater Tanks where a Public and outdoor cleaning. Most can you catch? Supply is Available published by rainwater has very low levels of NSW Health. Before implementing any large dissolved solids that can make scale rainwater collection system, it well suited for cooling towers. To maximise the amount of you need to be aware of the size Make sure you are aware of water and money you save with of your catchment and the likely the properties of rainwater you a rainwater tank, it’s important annual rainfall you will receive. collect from your site before you that you maximise your use of use it in cooling towers. rainwater. This can be achieved by using rainwater where it will be used frequently such Photograph 10 – Rainwater captured in tanks at Investa’s 73 Miller Street building in North Sydney, is used to irrigate gardens on the building’s rooftop and balconies. 97 98 3 Chapter 20 – Rainwater Chapter 20 – Rainwater 3 You can refer to the Australian Rainwater quality A ‘first flush device’ will also Plumbers must complete all Costs and benefits of Bureau of Meteorology’s improve rainwater quality. The work in accordance with the rainwater tanks The quality of rainwater website at www.bom.gov.au device sits between the roof NSW Code of Practice Plumbing collected will depend on the Rainwater harvesting is a popular for data about average annual downpipe and the rainwater and Drainage and follow the location in which rainfall way to conserve drinking water, rainfall and mean days of rain storage tank and will dispose specific technical requirements occurs, as well as the surface although it is usually less cost for many locations in Sydney. of the first rainfall runoff for rainwater tank plumbing it falls onto and the standard effective than other measures collected by your roof. Because that are detailed in Guidelines of storage tanks. Rainfall in an for reducing water consumption, You can calculate the theoretical the first flush contains a higher for the Installation of Rainwater industrial area is more likely such as leak reduction and maximum rainfall that can concentration of pollutants, a Tanks on Residential Properties, to collect airborne pollutants improved efficiency. However, be captured by multiplying properly sized first flush diverter Part 1 Plumbing requirements. and roof catchment areas are rainwater tanks are easy to your roof catchment area is very effective at improving the more likely to be polluted with install and a strong visual (in metres) by the average quality of collected rainwater. For more information, settled particulate matter. symbol for water conservation. annual rainfall in metres. contact Sydney Water’s Use mesh covers and strainers Plumbing Policy, Standards Rainwater collected from paved Rainwater is not governed by It is likely that the amount of on the inlet and overflow of and Regulation Group at: areas including carparks and water restrictions and can be rainfall you can capture in a the tank to prevent mosquitoes roads is typically referred to [email protected] freely harvested to irrigate given year will be up to 20 per and other insects from getting as stormwater and contains parks and gardens. Rainwater cent less than the theoretical into the tank and breeding. This You should also contact your significantly higher levels harvesting also reduces maximum because of losses will improve water quality and local council to discuss the of pollutants. The capture, stormwater discharges from from evaporation in small rainfall prevent your tanks from causing regulations that apply to treatment and reuse of commercial sites, which reduces events, infiltration into roof a public health nuisance. the installation of rainwater stormwater is covered in stormwater flows into the materials, overflows from gutters tanks, stormwater reuse Chapter 21 of these guidelines. local environment and reduces and tanks during heavy storms systems and greywater or Plumbing requirements stormwater volumes during and losses to first flush devices. black water reuse systems. The roofs of commercial and approvals rainfall. It can also be a visible buildings may collect For a rough calculation of how If your tank is going to require In New South Wales, property and low risk measure when contaminants like dust, leaves, much water you may be able to top up from mains water, which owners can install tanks of compared to reuse options. vegetation, bird faeces and save with a tank of a given size, is likely if tank water is likely up to 10,000 litres without occasionally dead animals. you can use online calculators at to be used for needs such as development approval – Equipment and cleaning Keeping roofs clean with regular toilet flushing or cooling tower providing conditions such as https://egrants.com.au/ maintenance will improve the Keep your roof catchment operations, you will need to siting, installation of first flush watertankmodel/index.asp quality of collected rainwater, clean, install an adequately comply with backflow prevention diverters, noise mitigation and reduce the likelihood that sized first flush diverter and To more accurately model containment requirements and mosquito control are covered. gutters and collection systems remove sludge from tanks every tank sizes, you need to use install a backflow prevention Larger tanks or tanks that do not get blocked and reduce two to three years. Your tank daily rainfall data, understand device at the property meter to comply with these conditions the amount of treatment water should remain quite your average daily water use protect the mains supply. usually require local council that will be required. clean and you will not need and incorporate variables development approval. complex treatment systems. such as temperature and seasonal variability. 99 100 3 Chapter 20 – Rainwater Chapter 20 – Rainwater 3 To use tankwater, you usually Converting onsite • it might be necessary to treat need to install good quality detention tanks stormwater from some areas pumps to ensure adequate before it is diverted to your Many commercial buildings operating pressure. You also storage tanks. If you have more have been constructed with need a reliable device to than one OSD tank, it might large on-site detention (OSD) switch between rainwater be possible to separate your tanks for stormwater. These and mains water supply. It is stormwater and rainwater tanks are designed to capture common for poor quality and collection so that you can rainwater and stormwater after badly maintained pumps to use each water source for heavy rain, and slowly release it fail and this can jeopardise purposes appropriate for to the main council stormwater the success of your rainwater their different quality. system so these systems do harvesting operations. not become overloaded. Useful documents Your plumbing contractor or There is increasing interest in hydraulic engineer can advise NSW Health Private Water converting these tanks to storage on the costs and installation Supply Guidelines 2007, NSW tanks. You should consider: of this equipment. Health, www.health.nsw.gov. au/public-health/ehb/water/ • using your OSD tanks may You will need to clean your tank private_supplies.html make design easy because regularly to remove accumulated rainwater collection has sediments. The technique used Guidance on the Use of been centralised, i.e. there will depend on the type of tank Rainwater Tanks 2004, is little need to consolidate you have installed. Advice on Environmental Health downpipes that drain how to clean tanks is provided Monograph, enHealth Council, different parts of the roof in ‘Useful documents’ section of http://enhealth.nphp.gov.au/ council/pubs/documents/ this chapter. • OSD tanks will often also rainwater_tanks.pdf take stormwater from paved common areas (like shopping Use of Rainwater Tanks Where a centre forecourts), footpaths, Public Water Supply is Available, Case Study carparks and internal roads. June 2007, GL2008-09, NSW Lend Lease Retail This is likely to increase Health, www.health.nsw.gov.au/ pollutants including oils and policies/gl/2007/GL2007_ greases in the captured water, Lend Lease Retail operates Macarthur Square Shopping Centre in Campbelltown, in the south 009.html which may reduce the uses west of Sydney. Lend Lease is collecting rainwater from the centre’s roof, storing it in a 250 kilolitre of this water, or necessitate underground tank and using it for toilet flushing and garden irrigation. additional treatment Photograph 13 – Part of the extensive roof top area at Lend Leases’ Macarthur Square in Campbelltown. This roof top is a catchment for 250 kilolitres of rainwater storage. 101 102 3 Chapter 20 – Rainwater Chapter 20 – Rainwater 3 Case study Blackmores Blackmores is one of the leading Australian manufacturers of natural health supplements. It is constructing a new head office building and distribution centre in Warriewood on Sydney’s northern beaches.