What is rainwater harvesting and how does it work?

Rainwater harvesting is the capture, storage and use of rainwater. Anybody can do it and it can be designed and customized to suit the needs of the user (potable water from rainwater for example).

There are several types of rainwater harvesting systems, the following three are the main ones:

In-situ rainwater harvesting refers to the capture of rainwater where it falls. This system is useful in agricultural production systems where micro-catchments are used. For example Zai Pits ( Wikipedia Zai-Pits).

Run-off catchment is another rainwater harvesting system. Rainwater running of surfaces is channeled through pipes or trenches and collected in storage structures like tanks, ponds, swales (Wikipedia Swale ) and dams, to be used at a later stage or for attenuation and/or infiltration.

Then there are roof catchment systems. These involve capturing rainwater from roof tops and storing it either above or below ground tanks made from plastic, concrete or metal. 

Some facts:

• In New Zealand around 10% of the population depend on roof collected rainwater.
• ~ 18% of total water consumption is used for flushing the toilet (domestic).
• ~ 23% of total water consumption is used for the washing machine (domestic).
• ~ 41% ( probably more if you add garden irrigation and outdoor use)  of total water consumption could be covered by rainwater
• ~ 27% of total water consumption is used for showering (domestic)

(Watercare)

• Average water consumption per person in New Zealand  227 liters / day (Learnz). Water consumption varies quite significantly between the regions (Queenstown Lakes District Council 416 liter/day)

Advantages of Rainwater Harvesting

1. Low-cost Maintenance
You really don’t need to invest much money to keep the systems going. Purifying the water is not necessary if you don’t intend to drink the water.

2. Lower Water Bills
You can use your collected rainwater for flushing toilets, washing your clothes, and watering the garden. This’ll help in keeping your water bills to a minimum. (Sample system) 

3. Great for Irrigation
Rainwater is pure rainwater without any added chemicals into it so you can make sure that this is reliable for irrigation. (Sample System) 

4. Reduces Ground Water Demand
As our population increases, so does the demand for water. In many areas, we are reliant on dams, rivers  and aquifers for our water sources.

5. Reduces Soil Erosion and Floods
By collecting rainwater, you can minimize the likelihood of flooding around your home and reduce the load on the council stormwater system.

6. Multi-Purpose
You can use rainwater in flushing down toilets, washing your cars and motorcycles, and etc. (Sample System)

Disadvantages of Rainwater Harvesting

1. Unreliable Rainfall
Rain doesn’t fall every day making it hard for you to collect some daily. However, for example, Auckland and other part of the country does not suffer from this compared to other centers.

2. Starting Costs
If you choose to have a rain harvesting system, then the time to implement these systems is when you are building your home as the additional costs are recovered quicker. Allocating funds for a system installed in your home is money well spent and will add value to your home.

3. Chemical roof seepage
Some roof coatings may contain harmful chemicals so it is advisable to talk with one of our consultants first to ensure your roof meets the guidelines.

5. Storage limits
There is a practical limit to how much water you can store on your property and is often limited by your section size and appropriate locations for the tanks . Especially in winter, the rain captured will be greater than the capacity of the tank. Rainwater tanks have to be designed to deal with this situation and to release the excess water to the council stormwater system  in accordance with council requirements.

Rainwater Harvesting is a win-win situation for building owners, councils and the environment.

We can give you advice what systems will suit your needs and what is involved.

www.aloaqua.co.nz   /   [email protected]  / + 64 3 2600 589

Every dwelling, domestic and commercial, should have a rainwater harvesting system! Here's a quick overview what is required in terms of material in order to use the water inside the dwelling for flushing toilets, the washing machine and for irrigation.

By the way, the Homestar rating system offers up to four points for dwellings which reduce the consumption of potable water in and around the dwelling through the collection and use of rainwater.

Apartment developments are also rewarded for incentivizing conservation through individual metering of each dwelling. A water calculator is used to estimate the percentage of household water demand able to be met with rainwater: 

 Standalone and Terraced Dwellings

(1)

The dwelling has a rainwater harvesting system with a minimum connected roof catchment area of 30m2 per dwelling, connected to a tank with a minimum rainwater holding capacity of 500L per dwelling, with at least one connection to a tap for outdoor water use. 

0.5 points

        The rainwater harvesting system is connected to and can meet all or part of the water use demand    from, laundry, outdoor water use, toilets and dishwasher. 

Up to 3.5 points

Apartments

(2)

The development has a rainwater harvesting system with a minimum roof catchment area of at least 30% of available roof area, connected to a tank with a minimum rainwater holding capacity of 5000L, with at least one connection to outdoor water use and /or common area water use. 

0.5 point

       The rainwater system is connected to and can meet all or part of the usage demand from, laundry (common or individual) and / or toilets and / or dish washing in every dwelling where points are claimed. 

Up to 2.5 points

      Each apartment dwelling has a separate water check meter that enables each apartment to be billed separately for its water use.

1 point

Rainwater Harvesting System 1

(up to 3.5 points for standalone and terraced dwellings)

In-ground or above ground tanks possible (not included in the below mentioned price)

Material required:

• RURAIN filter DN 100                  4. Suction hose 1/2”  5 meter
• PLURAFIT calming inlet DN 100 5. Wall bushing DN 100 (if required)
• Floating suction device ½”           6. RAINMASTER Eco10

Tank sized according to requirements and space available. Different shaped tanks and colors available.

RAINMASTER ECO comes with mains water top up connection and switches over to mains water if the water level in the tank reaches a critical low.

 Budget Price (supply only):  NZ$ 2,425.-  + Gst + Freight   (tank not included)

Rainwater Harvesting System 2

(up to 3.5 points for standalone and terraced dwellings,

Apartments up to 2.5 points)

In-ground or above ground tanks possible (not included in the below mentioned price) 

Material required:

• PURAIN filter DN 100                   4. Pressure  hose 1”  5 meters
• PLURAFIT calming inlet DN 100   5. Ground bushing DN 100 (if required)
• Submersible Pump set MULTI-05  6. RAINMASTER D24 fill-level indicator

Tank sized according to requirements and space available. Different shaped tanks and colors available.

A drinking water top-up switches on automatically for periods of shortage and supplies the cistern or tank to a set level.

 Budget Price (supply only):           NZ$ 2,645.- + Gst + Freight  (tank not included)

 Please note:

This is a guideline only; bigger pumping units might be required, dependable on the size of the house, number of apartments, toilets, washing- and dish washing machines.

Contact:  ALOAQUA Ltd,  [email protected]   www.aloaqua.co.nz 

                phone: +64 3 26005879

 Aloaqua Ltd,  "Conditions of Supply and Sale" apply and are available on request.

Using rainwater for flushing toilets and washing machines is maybe something new in New Zealand, but is already standard in most European and other countries. Solutions using rainwater for various applications offer new possibilities for property owners, developers and councils.

Rainwater is of such good quality that it can be used as potable water, with the right technology. No bacteria, nitrate and chemicals and instead soft water which causes no calcification in pipes, hot water cylinders and on surfaces.

Mitigating the effect of storm water run off from properties, by retaining and using it on site, reducing the volume of potable water use and offering new areas of work for installers.

Examples of rainwater harvesting and utilization systems: www.aloaqua.co.nz

One manufacturer of rainwater harvesting and greywater recycling equipment in Germany has started to brew it's own beer from rainwater (Brain - http://www.brainwaterbeer.com/) to showcase how good it taste (I had a bottle and it taste really nice).

Rainwater attenuation, - retention

The increase of sealed surfaces in urban areas put additional pressure on the existing stormwater infrastructure. More and more councils require now rainwater attenuation/ retention systems to be installed for new developments. Innovative systems that are cost effective, space saving and require low maintenance are already used in densely populated areas in Europe. More information: Rainwater attenuation/ retention

 More info:  www.aloaqua.co.nz

 contact:      ALOAQUA

 Phone:       +64 3 2600 589

   email:       [email protected]

Rainwater Infiltration - Complete solutions for trench and trough-trench infiltration

Trench System

Trench systems are ideal when the surface above the infiltration system shall be usable, parking, playground etc.

Trough-Trench System

The polluted rainwater is cleaned via bio-active soil and seeps into the underlying trench, where it is stored short term to infiltrate.

Rainwater Retention / Attenuation - to ease pressure on public drainage infrastructure

Trench System

Rainwater is filtered through a sedimentation/ filter shaft, then stored short-term in the in-ground trench and slowly released via the throttle outlet. The system can remain open at the sides and bottom if local infiltration is allowed or desired. The tunnel elements are placed in a layer of EPDM material if a closed system is required.

Under- or above ground Systems

Selection of interconnected tanks, scalable to meet council and local requirements.