Drain slope 20mm per m
In New Zealand, the average person uses 227 litres of water per day:
- Toilet = 86 litres per day
- Bathing and hygiene = 68 litres per day
- Laundry = 36 litres per day
- Kitchen = 32 litres per day
- Housekeeping = 5 litres per day
Rainwater Harvesting
Rainwater Harvesting Calculator 2 Adults, 2 Children. 5000l per person. 30,000l tank $4,700
Use roof over deck 15m x 6m, roof over septic 20m2. Approx $2,000 for posts and roof.
| Area | Minimum Roof Area | Tank Required – 4 people |
| Northland | 225m2 | 25,000l |
| Auckland | 225m2 | 25,000l |
| Waikato | 280m2 | 25,000l |
| Bay of Plenty | 225m2 | 25,000l |
| Taranaki | 200m2 | 25,000l |
| East Coast | 270m2 | 25,000l |
| Hawkes Bay | 350m2 | 25,000l |
| Manawatu | 280m2 | 25,000l |
| Wairarapa | 280m2 | 25,000l |
| Nelson | 350m2 | 25,000l |
| Canterbury | 450m2 | 25,000l |
| Central Otago | 480m2 | 25,000l |
| Southland | 250m2 | 25,000l |
With basic pre-collection filtering, rainwater is good for irrigation, flushing toilets, laundry, and even bathing.
Your roof is bound to gather some murk and dust no matter how clean you keep it. Rain washes down all this dust the very first time it falls after a while. The result is dirty water that you shouldn’t bother collecting at first.
Creating a system that gathers at least the first three gallons (or more, depending on your roof size) of water before letting the rest flow to your main storage tank is a good way to ‘filter’ out this dirt.
You can use a simple system like a couple of dropper pipes (or small containers) on a horizontal running pipe. The idea is the water won’t flow past the reservoir the dropping valves until they are full. This means that they will gather the first flush of water and on cleaner rainwater will flow through to your tanks.
Tanks need frequent washing. This varies depending on your tank type. Don’t go for more than a year without cleaning yours. Doing it twice a year or immediately after winter is a good idea.
About 0.5-1 litre per m2 of roof area for ‘First flush’, depending on pollutants.
Superhead First Flush and Rainwater Filter
Superhead.com.au
Superwall Systems
102 Walters Drive
Osborne Park. Western Australia 6017
Phone: 08 94674044
Collect this water to use for irrigation.
Install a calmed water inlet system to reduce sediment.
rainwatermanagement.com/pages/wisy-4-step-process
Pre-tank filter
Before entering the tank for storage, rainwater should be both filtered and aerated. Filtration removes large particulate matter, which frequently both carries and feeds bacteria. Removal of this particulate matter, along with oxygenation of the water, greatly reduces the number of harmful bacteria in the tank.
WISY pre-tank filters accomplish both of these tasks, protecting the water quality in the tank.WISY Filtersare also self-cleaning and require minimal annual maintenance.
Smoothing Inlets
Smoothing Inlets are designed to direct the water upwards upon entrance to the tank. This prevents disturbing the healthy “bio-film” that has settled at the bottom of the tank. The rush of water directly into the bottom of a tank without a smoothing inlet would stir up fine sediment (think of quickly pouring water into a fish-bowl) that could then be drawn in by the pump. The “bio-film” at the bottom of the tank actually works to eat any bad bacteria that may enter the tank and help create a healthy water environment.
How to Prevent Your Water from Going Anaerobic
Untreated water will start smelling foul after a couple of weeks in storage due to microbial growth and other organic infestation. You can avoid this by adding some chlorine to the water. mix non-scented NSF-approved household bleach (5.25% chlorine) in the reservoir at the ratio of 1 gallon of bleach for every 1,000 gallons
If you won’t store your water for long and don’t want to add chlorine so early in the collection stages, you can use alternatives that keep the stored water circulating. A calmed inlet delivers the water to the bottom of the tank instead of just dumping it through the inlet positioned at the top
Push the pipe delivering water to the bottom of the tank and use a U joint to angle it upwards. The incoming water will induce a flow in the water hence stirring it up without disturbing any sediments at the bottom of the tank.
You can get rid of any residual smell in the stored rainwater by adding an activated carbon filter down the line.
Always have a plan to biologically treat your water. Chlorination is the easiest way to kill bacteria and other biological contaminants. If you don’t want chlorine in your water, explore other options like boiling, Ozone treatment or super fine bacteria capturing filters.
When dealing with rainwater, you should go for filters as large as 50 microns at the very start to eliminate all visible large particles that makes your water dirty and gross to the eye.
- You can use chlorination, ozonization, UV light to kill the microbes
- Go for finer filters
- Try membrane filtration
- Boil the water
- Solar pasteurization
Filter to the Required Level
Filters are expensive and require replacement the more they work. A good way to keep your rainwater harvesting costs low is filtering only as much as you need to.
For instance, combining a 50-micron filter (or finer) with a solar pasteurizer or another disinfection method should be good enough for your dishwashing and showering water.
Using a dedicated filter and disinfection system for your drinking and cooking water will ensure that you don’t using the expensive and finer system to filter gallons of water that you will end up flushing down the drain.
Water Pressure
FloJet 02840100A Marine High Volume Water System with Accumulator (4.5+ GPM, 40-PSI, 12-Volt, 11-Amp)
amazon.com/Flojet-02840100A-Marine-Accumulator-12-Volt
House Water Processing
Express Water RODI10D Reverse Osmosis Deionization Water Filtration System – 6 Stage RO Water Filter with Faucet and Tank – Under Sink Water Filter
amazon.com/Express-Water-Deionization-Reverse-Filtration
98,000 Litre lifespan – 22 years for 8 people at 1.5l/day. One per household, plumbed to drinking water tap.
In general, PFOS and PFOA resist most conventional chemical and microbial treatment technologies. The strongest proven technologies to filter PFAS out of drinking water include granular activated carbon absorption, ion exchange resins and reverse osmosis.
Purefast™ filter cartridge for PFAS
DEXSORB for PFAS in filter block for use in:
- Faucet Mount
- Under-the-Counter
- Refrigerator
- Whole Home
cyclopure.com/product/purefast-filter-cartridge-for-pfas
Pre Storage Water Processing
Water from gutters processed with reverse osmosis before entering storage tanks.
Water Tanks
To pressurize cold water (Run one at tank outlet to a manifold that supplies each house. Put stopcocks at each manifold outlet to act as a toby water shutoff in case of maintenance):
If the water is to be used for human consumption the plastic material must actually comply with the requirements of potable-water standard (AS/NZS4020: 2002 Potable Water Standard)
2x 25000l to supply all properties
Water from roof. Filter and UV before entering tank so stored water is clean.
Tanks must comply with AS/NZS 4020:2005.
Hot Water
A fully insulated hot water ring mains system will keep the hot water circulating, so there is no need to wait for the water to heat up when you turn on a tap, which conserves water and saves energy.
Hot water cylinders use a lot of power and tend to run for at least a few hours a day. A typical water heater runs at 3000W and running for about 3 hours a day will use 9KWh. 30% of the electricity bill. It takes 5 hours at 3kW to heat a cylinder of water from cold. One minute per litre, as a minimum for a modest temperature rise, so at least 210 minutes. One and a half minutes per litre to get really hot if starting very cold, so up to 315 minutes
Minimum temperature 60oc in cylinder and 55 oc at point of use.
Tank will handle more than 100 oc assuming it is under mains pressure, more like 130 oc (assuming mains pressure at 2 bar) however typically solar controller should be set to stop pumping at 85 oc as this prolongs the life of all the hardware, including the tank.
Thermostats must be on timers (Off at 8.30am, on at 7.30pm). Water will lose between 1 kWh and 2.5 kWh of heat per day. As an estimate, the water in your tank should stay hot for a day or two.
So – 3 hours to produce 2.5-3kW in winter. 4 solar panels Wired in series to equal 48v
DC Twin Core Hot Water Element. 12v, 24v, 48v powerspout.com/products/dc-twin-core-hot-water-element?variant=4968610496549
plumbingplus.co.nz/products/rheem-420l-solar-storage-with-electric-boost
Heat water direct from solar panels powering the 48v HWC element. Heat to maximum operating temperature possible, temper water at exit.
Usually, hot water pipes run ‘Uphill’ to ensure the hot water rises to the tap.
Put stopcocks at inlet and outlet of tank for maintenance. Add pressure relief valve.
Firefighting Water
You will be required to install a 30,000 litre storage tank located within 90m of your house that has hardstand access for a fire appliance. A firefighting reserve of 20,000 litres must be maintained at all times. Other forms of water storage, such as irrigation storage dams are acceptable alternatives, but require the written permission of the NZ Fire Service to be supplied to Council.