Written by John Williams
Auckland finds itself in recovery mode after enduring a record-breaking drought, which saw 40 percent less rain than normal fall in our catchment areas (Nov-May 2020). The latest news is that the dams are currently around 68 percent full, which is still more than 20 percent below historic levels.
Watercare says that Aucklanders have done an amazing job so far – saving four billion litres of water since restrictions were introduced in May. However, despite this Herculean effort, water restrictions remain in place across the whole of the region, which is particularly worrying, considering the long, dry summer months that lie ahead. The clear message is that we need to continue to be vigilant when it comes to our water usage.
Without labouring the obvious, there are three ways to conserve the water we use each day: number one, restrict the amount of water coming into our homes; number two, use the water that does come into our homes wisely; and, number three, collect or re-use water.
The first two are covered off later in this article, in the section ‘Household Water-Saving Tips’. And to be fair, if we all collectively and diligently took on board just half of these suggestions, it would go a long way to relieving the immense pressure that is currently being put on Auckland’s water resources.
The third way to take the weight off our reticulated water supply is to collect what is delivered free from the skies, and/or re-cycle what we have already used, before it is returned to our waterways.
Fresh drinking water, as we have discovered lately in Auckland, is a limited resource. Not only is it in short supply, it also takes energy to make it fit for consumption and to transport it to our homes, so why put it straight back onto the garden, or flush the loo with it?
To help explain your options when it comes to either collecting and using rainwater, or recycling waste water from your home, we enlisted the help of Jo Woods, Built Environment Sustainability Consultant at Revolve Energy and joint designer of the Zero Energy House project.
An outdoor use rainwater collection tank is relatively simple and inexpensive to connect up to an existing building, and the benefits are ongoing. Most can be connected straight to the downpipe from your roof and should have some way of overflowing back to the drain if they become full. The tanks are small(ish), made from plastic, and sit above ground. If you opt for a lidded tank, rather than an enclosed one, make sure they come with a child-proof lid.
Rainwater is an excellent source of water for irrigating your garden, and a similar collection system can also be set up to supply water for washing your clothes, flushing your toilets, and – if it's properly treated – for drinking and other household uses.
Generally, rainwater systems that collect water for outdoor use only do not need a Building Consent. Systems that also collect water for indoor use are more expensive, come in two types, and will both need consent.
Type one: Outdoor use, plus toilet flushing and clothes washing. This requires a backflow preventer, where the main supply is connected as a back-up to this system. Water treatment, such as UV or filtration, may also be required by Council. For - a system with good collection area and storage volume, you could see savings of up to 50 percent of your mains water. These systems should have a ‘first flush’ function fitted, which diverts the first few litres of rainwater from the roof to the stormwater or sewer line, to ensure that dirt washed off the roof doesn’t enter your collection tank. This type of system also requires two supply pipe networks in the house – one for potable water and one for rainwater.
Type two: All water use, indoor and outdoor, including drinking. This requires a tank that is suitable for potable water and must be treated to drinking-water standards. A backflow preventer may or may not be required, depending on the system design and whether there is a main connection. Again this needs a ‘first flush’ function and treatment with UV and filter.
Grey water is wastewater from taps, showers, the bath and from your washing machine. It doesn’t include kitchen wastewater, as this contains food particulates. One of the key benefits of reusing greywater is that it is available all year round. However, there are restrictions to its use, as it contains chemicals, particulates and bacteria, etc. A greywater system also requires a Resource Consent (for discharge to land, garden irrigation) and a Building Consent (for reuse in toilet flushing).
Grey water systems are far easier to install in new buildings than to retro-fit into an existing home, as they require two wastewater pipe networks – one for greywater, one for blackwater (sewerage). They come in two types – Direct Disposal or Storage:
- Direct Disposal goes straight to landscape irrigation and is deemed safer, as there is no time for bacterial growth. The greywater has minimal treatment and therefore there are restrictions around disposal (ie. must be beneath ground) and proximity to edible planting. These systems are best installed with a sensor that detects when the ground has reached saturation (to avoid overflow) and drain to sewer instead. They should also be installed with an accessible manual changeover switch, so that disposal to sewer can be used under certain conditions, such as washing nappies, or using chemicals not suitable for greywater systems. The regulations for these types of systems are very strict, so can be very difficult to get consented in Auckland urban areas.
- Storage systems are used when the grey water is reused for toilet flushing. Stored grey water needs regular chemical treatment (with chlorine) to avoid build-up of harmful bacteria.
Cost vs Benefit
Woods says collecting rainwater directly from your roof for use on your garden probably makes the most sense financially, and are particularly worthwhile for edible gardens, plus the systems are easy to install without needing a Building Consent. It goes without saying, though, that underground rainwater storage tanks are more expensive to install than overground tanks.
Generally, because of the relatively low cost of water, but the high capital cost of installing a plumbed-in system, it's unlikely that either rainwater (with inside water use) or grey-water systems make economic sense in the short term. Some of that capital cost will be due to dual-plumbing systems (separate plumbing for mains and rainwater, and grey water and black water), which will vary on every project, depending on pipe run lengths.
Because of the need for dual plumbing, homeowners would probably only consider incorporating this type of system when embarking on either a new build, or a major renovation, as it needs full access to walls and underfloor spaces, as well as digging up the garden to run the piping.
Watercare and Auckland Council also require you to pay the Infrastructure Growth Charge (covering mains connection and meter fee) on every new build, if near mains supply, which is about $12,000 (excluding GST), making the economics of rainwater and grey water not very favourable. This is a flat rate for all. There is no reduction for being more efficient with water use. Resource Consent fees for grey-water irrigation systems will be very site dependent, but generally inner city sites will struggle to get consent due to the current regulations being written for rural black-water systems rather than urban grey-water systems.
To help consumers make informed decisions, all products and appliances that use water that are manufactured in, or imported into New Zealand, must clearly display star-rating labels that comply with the New Zealand Water Efficiency Labelling Scheme (WELS) regulations, to show how water-efficient they are. These include clothes washing machines, dishwashers, lavatories, showers and taps.
Some Household Water Saving Tips
Watercare is asking every Aucklander to reduce their water consumption by 20 litres a day. According to the BRANZ WEEP Study, New Zealanders use an average of 168 litres of water per day – so 20 litres should be easily manageable for all of us. Most of the suggestions below from Watercare are simple, inexpensive fixes, or common-sense changes to bad habits that will not only save water, but also reduce your energy bills.
• Consider installing a showerhead with a low flow rate. Your hardware or plumbing store will be able to advise you on shower heads with low flow rates that match your shower fitting. Check its water rating label.
• Install a simple, inexpensive tap aerator on your bathroom tap to reduce the flow rate by up to 50 percent. You can buy them from a plumber or hardware store, or from environment trusts.
• Turn off the water when brushing your teeth or shaving. By doing this, you will use around 1 litre of water instead of 5 litres.
• Check for leaks. Small drips leaking from your toilet cistern can waste thousands of litres. Put a few drops of food colouring in the cistern. If colouring ends up in the toilet bowl without flushing, you have a leak. Have it repaired.
• Do not use your toilet as a flushing rubbish bin. You not only waste water, but also risk causing a blockage in your plumbing.
• If you need to replace your toilet, consider buying one with a dual flush. Check its water rating label. The latest four-star toilets use as little as 3 litres for a half flush and 4.5 litres for a full flush. Most toilets in Auckland use around 7 litres per flush and older toilets use around 12 litres per flush.
• With modern dishwashers, there is no need to rinse your dishes first. If your dishes are not clean after going through the cycle, you may need to clean or repair your dishwasher.
• When hand-washing dishes, fill the sink rather than rinsing and washing the dishes under a running tap.
• A simple tap aerator on your kitchen tap can reduce the flow of water into your sink. A swivel tap aerator has two flow settings and allows you to direct the water to where it is needed. Tap aerators are inexpensive and available from hardware or plumbing stores and environment trusts.
• Use a bowl to scrub vegetables in the kitchen sink. You can pour the water on your plants.
• Keep water in a covered jug in the fridge. It saves running the tap to get cold water.
• Rather than running tap water over frozen food to thaw it, plan ahead and let it defrost in the fridge for a few hours. If you are in a hurry, the microwave is a more efficient option than running water.
In addition to these water-saving tips, Watercare offers a free water audit that will give you personalised advice on how to make your house more water-efficient. To register for your free audit, call Watercare on (09) 442 2222, then press 3, or email to firstname.lastname@example.org