The eventual water outcomes you achieve in your home will be influenced at many stages during your project, and will require input from designers, builders, and suppliers of systems as the project evolves.
Key stages for incorporating water sustainability in your project and methods you can use to achieve your objectives are listed below. Your objectives around water, and the amount of certainty you want to have in achieving those objectives, will help determine which you use.
1. Define your priorities and set objectives
The objectives that you have set and quantified as targets should be included in your Design Brief as early as possible. This will allow designers, consultants and suppliers to refer to them during the design process and develop strategies to meet them. Your objectives will be a key tool for decision making, as they can act as a framework when assessing the strategies and features available. Including them early will also increase the possibility of achieving solutions that are integrated into the design in the most harmonious and cost-effective way.
2. Estimate your water use
Sustainability consultants can help you create a water profile, which can be a useful tool for decision making and for sizing systems. A water profile is a detailed breakdown of your water use that takes into account the efficiency of appliances and fittings, as well as their frequency of use. It usually includes the following categories:
- Baths and showers
- Clothes washers
- Other uses (such as pools)
Consumption per day for each item within these categories is determined and results are presented in litres per day per person. The average Aucklander uses between 140 and 175 litres of water every day.4
A baseline profile can be created early in the design process that includes a series of assumptions, and can become more detailed and accurate as the design evolves. Creating a water profile can be essential if the project is off the mains supply and needs to be self-sufficient for all water needs.
3. Decide if a tool or certification is right for you
If you’re using rating tools, their objectives and strategies will also need to be incorporated early in the process, as they might dictate the way the design is approached. For example, some tools may require rainwater collection or award points for its use. Including space for tanks and pumps early in the process can ensure they will merge effortlessly with the design.
4. Prioritise and test design
Always start with the design of the building, and the design strategies that can best achieve your objectives for water performance, before selecting products or systems. Some design features will contribute to your objectives, while others might distance you from them. For example, relying on rainwater collection for your potable water requires a catchment area – usually the roof – that is able to meet your demand and this will need to be factored in when defining the layout and area of the house. Additionally, rainwater tanks can become part of a retaining wall if your house is on a sloping site or, if the Resource Consent requires the use of stormwater detention tanks, you could work out how these can provide rainwater reuse, turning a consenting cost into savings on your water bill. On the other hand, if one of your objectives is to reduce demand in the summer, including a pool will not be helpful in achieving it. The way outdoor areas are designed and managed will also affect your water use and the impacts your project has on the environment. Traditional landscaping requires constant watering, making up 12% of the typical home’s water needs in a year.5
In the summer, irrigation accounts for 18% of a household’s water use.6
Increasing porous surfaces, reducing lawns and using native and drought-resistant plants are strategies that will contribute to a more efficient landscape design. If a lawn is a must, there are grass species that become yellow in summer if not watered often but bounce back in winter. If your objectives around water include considerations about wider environmental impacts, stormwater management features such as swales – low tracts of land, especially ones that are moist or marshy – can also be incorporated in the project.
Testing the design throughout the process can verify if objectives and targets are being met. Updating you water profile will provide average consumption per person, while specialised software can help you understand if catchment areas for rainwater are enough to meet your demand or the portion of it you have determined.
5. Use systems and products to optimise the design
As the design process moves forward, systems and products will need to be considered. The selection of these will also be guided by the objectives you have set and should take into account their lifecycle cost, not just the initial investment (see the ‘Lifecycle Costs
’ article for more information).
Products should be considered from a holistic perspective, since they will impact objectives in other areas. For example, your use of hot water in showers and appliances can also impact your energy consumption because of water-heating requirements. The cost of heating one litre of water with electricity from the grid is eight times the cost of that litre of water itself. Also, if using rainwater you may require a pump, which will impact your energy use.
Decisions aimed at improving water efficiency can start with minimising your water use by making simple choices around fittings and fixtures such as:
- Low-flow showerheads
- Low-flow taps for bathrooms and kitchen
- Low-flow/dual-flush toilets
To further reduce your consumption, you can select efficient appliances including washing machines and dishwashers.
The Ministry for the Environment has a Water Efficiency Labelling Scheme (WELS)7
that can help you find products and appliances that use water more efficiently. Your washing machine is the second biggest user of water at home, accounting for 23% of your total consumption.8
Choosing one that has a high water-efficiency rating will help you save on your water bills.
If you are planning on being partially or completely independent from the town supply, your project may need to incorporate water catchment and reuse systems:
- Greywater systems reuse water from showers, washing machines and basins in your garden or toilets. Such systems reduce your overall water demand, as well as the pressure on Auckland’s wastewater infrastructure by reusing water that would be immediately disposed of otherwise.
- Rainwater tanks can further increase your independence from the mains and can be sized to meet different needs. Small tanks can reduce the amount of potable water used for gardening, while bigger systems can supply a significant portion of your household’s requirements for toilet flushing and clothes washing.
6. Build well
The quality of your project’s construction will determine the efficiency and safety of your home’s water supply, usage and discharge. Ensuring there are no leaks and that water pressure is not too high can save you a lot of money over the years.
During construction, large amounts of building-related waste such as chemicals from paint, concrete, sand, grit and dust can pollute stormwater runoff. In Auckland, stormwater is carried from the drains in the street directly into our waterways. Therefore, implementing waste management practices on building sites (e.g. setting sediment traps) helps keep our streams, rivers and coastlines clean.
7. Use your home intelligently
Once the project is complete, the way you live in your house will play a key role in achieving your water objectives. Even if you have implemented water efficiency strategies during the design stage, the following habits may prevent you from achieving your objectives:
- Low flow taps will not save much water if left open while brushing your teeth or shaving.
- Efficient shower heads will not perform as expected if you shower for half an hour every day.
- Highly rated appliances such as dishwashers and washing machines will not save water if used too often or with half-full loads.
- Gardens with native plants that are irrigated for extended periods of time will not reduce their watering demand.
- Additionally, keeping the following in mind will improve the way you use water at home:
- Avoid using your toilet as a rubbish bin. You will not only prevent blockages but also keep products and chemicals that can’t be processed by wastewater plants (e.g. synthetic antibiotics, microplastics and chemicals) from reaching our coastlines.
- When washing your car, use a bucket of soapy water and the hose just for a final rinse.
- Collect your greywater from the laundry in a bucket and water your garden with it.
- Check the water pressure to ensure it is not too high.
- Periodically check for leaks. Watercare’s Be Waterwise offers guidance on how to easily do this.