WATER

Regulatory Requirements

G12 of the Building Code covers water supplies. It requires the safe supply, storage, reticulation and delivery of hot and cold water. https://www.building.govt.nz/building-code-compliance/g-services-and-facilities/g12-water-supplies/

Emergency Backup

Humans (and their pets) need water to survive an emergency. How much water do you need in an emergency? WHO guidelines call for 20–40 litres, meaning a four-person household needs a minimum of 80 - 160 litres of water per day.

Radio New Zealand reported on the 05 April 2016 that Wellington Water told the City Council that residents were likely to need closer to seven litres of water supply in the event of an emergency, amounting to 140 litres per person (based on 7 litres/ 5 days+ 4 person house hold).

Reduce Dependence on Mains Water

Our water supplies are failing and water restrictions are in place in many communities. Harvesting can be used in order to reduce our overall water usage and to protect supplies.

Reduce your Water Bills

Councils and Water Boards will increase water prices as they look to recover the true costs of providing water to the community.

Environmental Reasons

Rainwater Harvesting reduces the damage to our creeks, water habitats and organisms caused by storm water runoff and rainwater is good for the garden.

Health Reasons

Perhaps you see the value in pure fresh natural rainwater. You do not want chemicals added to your drinking water. You wish to drink pleasant tasting water. Your water supply is salty or hard, has odours or contains heavy metals. You consider rainwater better for your family’s health and you want to take control of what your family drinks.

Water Usage

Rainwater Harvesting / Utilisation

Stormwater Attenuation

Stormwater attenuation involves the capture, detention and controlled release of stormwater volumes before they discharge into receiving environments.

Storm water attenuation/detention tanks temporarily store rainwater collected from the roof and other hard surfaces of the property after rainfall events and release the water into the council stormwater systems at a much slower rate to reduce short term peak outflows from properties and minimise the impact of the water on the local environment, reducing the risk of localised flooding.

This is fundamental in looking after our waterways, marine life and ecology.

Attenuation is vital in cities where public stormwater facilities can no longer handle high volumes of rainwater discharged by regular rainfall events due to our expanding urban sprawl.

New developments are often required to achieve “stormwater neutrality”, where post development run-off peak flows are not exceeded by pre-development flows for a specified design storm event.

This can be achieved by installing stormwater attenuation systems prior to development, significantly reducing the risk of:

● Flooding.

● Loss of habitat quality and quantity.

● Accelerated erosion and land instability.

● Altering the natural water balance.

● Negative community use.

Councils require various volumes of water attenuation (& retention) capacity throughout NZ depending on local rainfall and catchment parameters, but different councils have different preferred methods of achieving it, eg: Auckland has various SMAF areas (Stormwater Management Area Flow) which have a variety of alternatives for attenuation and retention, as well as different rules for specific sites depending on infrastructure constraints. New Plymouth prefers soak pits for almost all stormwater solutions and Wellington Water has devised Approved Solutions for some products, while still requiring specific calculation and methodologies for others. In Christchurch, there is a small site criteria or attenuation can be required for quite high rainfall events such as an 18hr 50yr event.

Permeable paving is another solution for stormwater attenuation. https://www.firth.co.nz/residential/ecopave/

Water Storage

Onsite water storage or retention refers to the capture and storage of rainwater to be re-used in households, reducing a household’s reliance on the mains water supply.

Stormwater storage/retention tanks store rainwater collected from the roof and other hard surfaces of the property after rainfall events to be used for non-potable uses. However it is recommended that hardstand areas bypass re-use systems if at all possible, to reduce the chance of contamination.

Note: you can’t attenuate and store from the same volume facility! Attenuation tanks must remain empty waiting for a storm event, when storage tanks need to be full for use as required. You could have a tank that was say, twice the size needed for attenuation so that when it was half full you could also use it for irrigation. However, there must be sufficient volume for attenuation requirements too.

Rainwater poses little health risk when applied to non-potable uses such as landscape irrigation or when used to flush toilets, fill washing machines and provide water to outside taps for cleaning and gardening.

It is recommended homeowners have ‘upstream filtration devices’ to prevent any leaf matter and debris entering the tank. Gutter guards OR leaf diverters installed on down pipes, as well as either a first flush systems or silt trap installed to prevent any kind of silt, soil, sediment, from entering the tank.

Using a tank made from ‘tank grade plastic’ and/or incorporating post tank additional treatment such as cartridge filtration or UV disinfection is generally required when rainwater is to be used as a potable supply to ensure it is safe for drinking.

A sufficiently sized retention system reduces a home's supplied water usage by 40-60%1 depending on the household's water usage. Homeowners may also want to install a retention system to reduce their dependence on town water supply in times of water restriction.

Based on the monthly average water usage of a 4 person household. (learnz.org.nz)

Hot Water Heating

Background

Every home has a hot water heating device and most have hot water storage devices. Nearly every New Zealander has a shower or bath using hot water at least once a day. Therefore, efficient hot water heating is a critical part of the performance of a Healthy Home.

Water heating energy consumption

BRANZ study report SR221(2010) Energy Use in New Zealand Households shows that water heating accounts for 27% of household energy use. https://d39d3mj7qio96p.cloudfront.net/media/documents/SR221_Energy_use_in_New_Zealand_Households_-_final_HEEP_report.pdf

Sanitary requirements

G12.3.5 Sanitary fixtures and sanitary appliances must be provided with hot water when intended to be used for:

(a)  utensil washing.

(b)  personal washing, showering or bathing.

For further information https://www.building.govt.nz/assets/Uploads/building-code-compliance/g-services-and-facilities/g12-water-supplies/asvm/g12-water-supplies-3rd-edition-amendment-12.pdf

Heat pumps are becoming a favoured option for water heating. Most of the year these will operate at a Coefficient of Performance (COP) around 4.0, i.e. each kW of electricity yields an average of 4kW of heat energy depending on what part of the country is lived in. In winter, they should be operated when the COP > 3.0, or when the ambient air temperature is at its warmest e.g. between 10.00am and 3.00pm.

Typically, in New Zealand the recommended hot water cylinder is 300L in size (or larger) for a family of four to five. But note that not all are fit for purpose.

https://www.stuff.co.nz/business/122991874/half-of-hot-water-cylinders-tested-not-up-to-scratch-eeca

Solar PV power can be used to supply the electricity to the heat pump via the household power supply to make things even more energy efficient. Solar Direct Hot Water systems are beginning to be superseded by the photovoltaic options on the market.

Greywater recycling systems

Water scarcity is becoming an ever growing concern in the world today. A tremendous percentage of potable water is currently being used to flush toilets, for irrigation and washing laundry.

“Grey Water Recycling” allows a household or community to utilise slightly used water for secondary usage, as for example, flushing toilets, washing machine and irrigation.

For further reading 12 Water\THE BENEFITS OF GREYWATER RECYCLING SYSTEMS.docx

Water Saving Appliances

New Zealand Water Efficiency Labelling Scheme (WELS)

All products manufactured in New Zealand or imported into New Zealand on or after 1 April 2011 must comply with the New Zealand Water Efficiency Labelling Scheme (WELS) regulations. The first WELS water efficiency label design was introduced on 1 October 2017. All suppliers of water-using equipment covered by the regulations must comply with the 2017 regulations and use the labels.

WELS only applies to the supply of, or offers to supply, these products:

● New clothes washing machines.

● Dishwashers.

● Lavatories.

● Showers.

● Taps.

● Urinal equipment.

The Superhome Movement recommends the following as being good practice:

● Washing machine WELS 4 star.

● Dishwasher WELS 4 star.

● Toilets WELS 4 star.

● Showers WELS 3 star.

● Taps Wels 5 star.

For further information https://www.mfe.govt.nz/fresh-water/we-all-have-role-play/choosing-water-efficient-products

System Design

Rainwater Harvesting and Utilisation (non potable use)

Diversion from the down-pipe to a tank (200l up to 500l).

Ideal for watering the garden and no building consent required (check to confirm with your council).

Filter collectors to be used for:

● Irrigation.

● Flushing toilets.

● Washing machine / Laundry.

The tank type and size depend on space available and your water requirements. Tanks come in a variety of shapes, sizes and colours; and can be installed above and in-ground.

The requirements are sealed downpipes, a basic filtration system, calmed inlet into the tank and a floating suction device to ensure that you get the best rainwater quality. The rainwater pump should have an automatic switch-over to mains water should the water level of the tank reaches a minimum.

Rainwater harvesting and Utilization (potable use)

Potable water can be used inside the house for all your usual requirements as well as irrigation.

Many people, especially those in rural areas in New Zealand, depend on rainwater as their only water source.

Rainwater can be harvested and used for personal use in urban areas, if it is treated in the right way. (Check with your local council as there are different regulations around the country).

However, at least one mains water connection (kitchen, for example) should be available in the house.

Tank type and size depend on space available and water requirements. Tanks come in a variety of shapes, sizes and colours; and can be installed above and in-ground.

There are several systems available on the market; the following explains the INTEWA AQUALOOP system how it is installed and works purely as an example. There are no chemicals are required for this system!

How it works

Rainwater from the roof is pre-filtered by the self-cleaning PURAIN filter (1) and enters the tank via the calmed inlet to avoid settlement disturbance on the bottom of the tank. Rainwater will divert to the storm-water system if the tank is full, a skimmer on the PURIAN Filter removes floating debris (pollen and dust) on the surface of the tank water.

The AQUALOOP membrane station (3) filters the water; it can be equipped with up to 6 membranes (5) dependable on the water volume required. The system is modular and can be designed for small dwelling s up to big commercial buildings.

The AQUALOOP controller (4) activates the transfer pump at the membrane station as soon as the water level in the “Clean water Tank” (7) reaches a minimum. Floating switches installed in both tanks ensure that the system works efficiently and can’t get damaged if the water level within the rain water tank falls below a certain limit.

Each of the AQULOOP membrane filters has 6m² of filtration area with pore sizes of nominal 0.2µm and removes up to 99.9999% of bacteria and 99.7% of virus. The membrane filters have a life expectancy of up to 10 years depending on the degree of use and are easy to replace. The membrane fibres are permanently hydrophilic, meaning they are immediately functional when they come into contact with water, drying does not damage the membrane.

A back flush pump on the membrane station is back-flushing the filter according to the controller settings and thus ensuring that the pores are free and the membrane not clogging up.

An INTEWA RAINMASTER pumping and control unit (8) is transferring the water from the “Clean Water” tank (7) via a floating suction device to the end user (Shower, sinks, washing machine, etc). It maintains a certain adjustable pressure within the system to ensure that sufficient water is available at all times. It switches automatically over to mains water supply if not enough treated rain water is available, and back if the water level rises again. Therefore, no loss of comfort at all time for the user.

A UV lamp (6) can be installed on the supply side of the INTEWA RAINMASTER unit should these be required.

The INTEWA RAINMASTER units are available in different sizes and can be connected in series.

The whole system is modular and can be designed to meet different requirements. It can be installed in a variety of tanks.

The system can also be used to treat surface, well or ground water.

(Photo1) INTEWA PURAIN Filter installed inside a tank. The Floating suction device is visible on the left side.

(Photo 2) INTEWA RAINMASTER Favorite 20, Pumping and control unit.

Stormwater Systems Ltd Products

FenceTank

FenceTank is an innovative detention and retention tank system designed to manage rainwater and stormwater for New Zealand homes. https://www.fencetank.co.nz/

For difficult sites where an above ground water tank solution doesn’t work, Stormwater systems also provides:

Aquacomb

Aquacomb is an innovative stormwater system that is capable of both retention and detention, designed to manage rainwater and stormwater for New Zealand buildings. https://www.aquacomb.co.nz/

Aquacomb can also be made from 100% virgin plastic if you require potable water retention. The pods are produced in two sizes: the 300mm high pod which is capable of storing 350L, and the 225mm high pod which is capable of storing 250L.

These pods replace the polystyrene pods in waffle slabs.

Recommended Healthy Home guidelines for Water are set out in the table below: