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Water Efficiency
Water is a precious resource in Australia, and one that we should all try to preserve through using it responsibly. This articles aims to give you some ideas on how to do so, from treating water, right through to water efficient fittings and appliances.
Treating Water
Water that is caught by a tank for use inside the home needs to be treated, as does grey water, black water, and storm water, which goes outside onto the garden or back into the water system.
Rain Water
Rain water tanks are able to provide a renewable supply of natural water that can be used for a range of purposes, and can actually be the primary source of water in some households. More information on using your roof to catch water can be found below.
To get the most use out of your rain water tank, a first flush device should be installed. These stop the first portion of roof runoff from entering the tank, reducing the amount of dust and debris that can accumulate on the roof from being washed into the tanks. Rain water tanks also need to be periodically desludged. The tank should be inspected every 2 to 3 years and desludging carried out if sludge is present. Professional tank cleaners may be available in your area.
Regular disinfection of your rainwater tanks should not be necessary but if you suspect that water is contaminated, you can chlorinate the water by adding some powdered swimming pool chlorine or liquid chlorine. About 5 milligrams of chlorine per litre of water will disinfect your tank. There should be at least .5 milligrams per litre of free chlorine 30 minutes after the chlorine has been added – you can test this using a pool chlorine test kit. You should be able to smell the chlorine faintly an hour after treating the water. If you can’t, you may need to add a similar amount of chlorine again. Ideally, do not use the tank for 24 hours after treatment to allow the chlorine taste and smell to dissipate and for harmful microorganisms to be destroyed.
Grey Water and Black Water
Grey water is the waste water that comes from the non-toilet plumbing fixtures in your home such as the shower, basins, and taps. Depending on what it is to be used for, grey water can require less treatment than black water and generally contains fewer pathogens. Treated grey water can be re-used indoors for toilet flushing and clothes washing, both of which use a lot of water. It can also be used to water the garden. Black water is the water that has been mixed with waste from the toilet. It requires biological or chemical treatment before re-use and should only ever be re-used outdoors.
To improve the quality of the water that you are re-using, minimise the use of cleaning chemicals, do not dispose of household chemicals down the sink, use a sink strainer in the kitchen, and use a lint filter on the washing machine. This will reduce the work that your treatment system has to do.
You will need to install a grey water treatment and disinfection system that provides a suitable level of treatment and that meets all the local regulations. You can divert grey water directly from the shower or bathroom sink drain to the toilet but it should not be stored for more than a couple of hours before re-use or disposal to the sewer. Domestic grey water systems need an accreditation certificate in order to be sold commercially in most states. An owner built system will generally need only Council approval.
Grey water can be filtered using a coarse filter, reed beds, and a sand filter. Aerated waste water treatment systems are also available. Disinfection is also required. Chlorine is the most commonly used method but ultra violet or ozone disinfection is also an option. The most common treatment systems in Australia are the septic tank, aerated/aerobic waste water treatment systems, wet composting systems, sand filtration systems, and electro-flocculation systems.
Storm Water
Improving the storm water that leaves the home is relatively easy and it can help to keep the waterways healthy. Victoria, as an example, now has standards for treating storm water to ensure that 80 percent of suspended solids, 45 percent of total nitrogen, and 45 percent of total phosphorus is removed from the storm water runoff. Treatments can include rain water tanks plumbed to the toilet, rain gardens, or porous pavements, rather than the standard concrete pavements.
Water Sensitive Urban Design
Water sensitive urban design (WSUD), is about the integration of water cycle management into urban planning and design. Its purposes are to protect natural systems, integrate storm water treatment into the landscape, protect water quality, reduce run off and peak flow, and add value while minimising development costs. Some methods for achieving these purposes in an urban environment include litter traps; swales – linear depression of channels that allow for storm water collection and movement; infiltration trenches – a shallow trench filled with gravel or rock into which runoff drains; bio-retention systems – storm water retention with vegetation; wetlands – to filter and correct the water; porous paving – where water can penetrate the paving; rain gardens – treat storm water and are also ornamental; rain water tanks – reduce the demand on drinking water supplies; and rooftop greening – vegetation on the roof to filter roof runoff and also the capture and storage of the roof runoff for reuse.
Design the Roof for Water Efficiency
The household roof is generally used to catch water that is stored in rain water tanks. The rain water can be collected from most types of roofs, including asbestos roofs, providing that they have not been painted with lead-based paints or coated with bitumen-based materials. Roofs that are painted with acrylic paint may contain dissolved detergents and chemicals that can affect the colour or taste of rain water. If you are using this water inside your home, for drinking or other purposes, you may need to discard the first few runoffs from the roof. New concrete tiled or metal roofs should also have the first few runoffs discarded.
To ensure that the roof is catching the most water available, consult with a roof plumber. They will be able to advise you on the best way to set up your roof to maximise water catchment. This may include more or wider gutters, extra downpipes or relocation of downpipes. You may incur an extra cost at the start, but it will more than pay for itself in the future once you are catching water. Also ensure that your gutters and downpipes are protected from debris such as leaf litter which can otherwise block the flow of water into the tank, or even contaminate the tank itself.
Water Efficient Fittings and Appliances
WELS is currently the standard for measuring water efficient fittings and appliances. By choosing to use more water-efficient products in the home, you will cut down on your water and energy bills and also save precious water supplies. As some examples:
- a water efficient washing machine uses only a third of the water than an older model does
- an old style toilet uses up to 12 litres per flush while a new dual flush toilet uses only three litres on half flush
- a standard showerhead uses 25 litres of water per minute while a water efficient showerhead uses as little as 7 litres per minute
The WELS scheme for measuring water efficiency applies to:
- showers
- tap equipment
- flow controllers
- toilet equipment
- urinal equipment
- clothes washing machines
- dishwashers
However, the scheme excludes secondhand products and products that have been imported into Australia for personal use.
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