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Written by Administrator
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Thursday, 31 May 2007 |
When considering the purchase of a new rainwater tank there are a number of issues that require your consideration:
- Your budget
- Legislative requirements
- Local planning regulations
- Use of the rainwater
- Security of supply
- What size Tank
- Tank sizing
- Tank Installation Above or Below Ground
- Location
- Tank material
- Installation
- Overflow discharge
- Filtration.
- Backflow
- Pumps
- Power supply
- Auto switching
Your Budget
There are a number of factors that may influence your budget:
- Whilst government legislation mandates a minimum size of 1000 litres for new homes and extensions over 50M², the additional cost of a larger tank can be quite small.
- An eco smart plumber can calculate the amount of water your roof will catch each year and can advise on the most suitable size for your home. There is no value in purchasing a rainwater tank larger than the capacity of your roof to recharge the tank or to put in a tank where water sits there not being used.
- Government and council subsidies and incentives need to be factored into your budget
Legislative Requirements
It is wise to check on the Planning SA website for the current legislative requirements for rain water tanks and your local council by laws before installing a tank.
Local Planning Regulations
Bylaws about rain water tanks vary from council to council so it is wise to check before installing a tank. Some councils require a minimum distance from a boundary fence. Some tanks can be used in place of a fence which may or may not be approved by your council. There may be mandatory requirements for the rain water tank/fence footings. Some councils require the installation of detention tanks to slow the flow of water into the stormwater system. By installing a larger tank it can be used as both a stormwater detention tank and as a supply to your home. In some rural areas a tank with a minimum amount of water must be retained for fire fighting purposes in the event of a bushfire. Again by installing a larger tank it can be used both as a fire fighting supply and as a water supply for your home.
Use of Rainwater
You need to carefully consider the uses you wish to make for the rain water you collect:
- Toilet flushing
- Laundry
- Hot water for the laundry, kitchen and bathroom
- Drinking water
- Gardening
- Car washing
- Other
The more you demand of the supply, the more water you need to harvest and store. If you wish to drink the rainwater you need to consider whether or not you wish to filter the water. If you wish to use only mains water for drinking and cooking purposes you need to decide how you will separate that supply from your rainwater supply. You may wish to include brushing your teeth in this decision.
Mains water also contains fluoride to reduce tooth decay.
Security of supply
The size of the tank needed will be influenced by the degree of security required. Securities of 90% or 99% mean the rainwater tank should supply the demand of water calculated for 90% or 99% of the time, respectively. Maintaining water supply under almost all conditions, including extended dry spells (high security), will require a larger tank than that needed to maintain supply under normal or average conditions (lower security). Lower security will mean water rationing or alternative sources of supply may have to be used more frequently.
What size tank?
To determine tank size:
- An eco-smart plumber can calculate the average consumption of the water using devices you wish to supply from a rain water tank to determine demand.;
- Find the rainfall for the area from the Australian Bureau of Meteorology.
- Ask an eco-smart plumber to calculate how much water you can harvest from your roof.
Tank Sizing
The SA Government has mandated that a minimum 1,000 litres rainwater tank must be installed for a new residence or a new house extension over 50m². However if space permits and you are connecting to multiple service points eg, laundry taps, toilets and a garden tap, you may want to consider a larger rainwater tank. If you are connecting to a hot water system, toilets, laundry taps and a garden tap you should consider an even larger rainwater tank which will provide much more water.
The SA Government has introduced a $400 plumbing installation rebate to assist with the cost of connecting an existing or new rainwater tank to the household plumbing. Some councils have now introduced Rainwater Tank rebates with other councils soon to follow, so it is suggested that you contact your local council to find out if they have a tank rebate system in place yet.
Tank Installation Above or Below Ground
Urban consolidation has led to increasing numbers of people living in courtyard homes, townhouses and home units where space can be limited. Modern tank designs can be accommodated in quite restricted spaces or can even be located in the foundations, under driveways or the garage of your home.
Location
The aim of rainwater tank installation is to capture as much water as possible and then to use it. Therefore the location of the tank is important. Connecting the tank to the guttering system that has the largest roof run off takes advantage of as much of the catchment area as possible. It is also very desirable to locate the tank as close as possible to the areas that will be connected to the rainwater tank.
Tank Materials
The range of materials that rainwater tanks can be manufactured from is growing each year. They range from
Concrete tanks In ground and above ground installation
Fibreglass tanks Above ground installation
Modular Steel tanks Above ground and areas where space is at a premium.
Round Steel tanks Above ground and where you may want to use an existing tank stand or where you have plenty of available space.
Bladder Tanks For above ground use only, they can be installed below the floors of the house or under raised decked patio areas.
Waffle Tanks Installed in the concrete slab at the construction stage of a new home’s foundations
Modular Polyethylene tanks Above ground for use in very confined spaces due to the depth of the tanks and can also be used as rainwater detention tanks if council requirements must be met.
Engineered Polyethylene tanks For in ground use only, these are made to take the weight of vehicles and are most suitable for installing in driveways, courtyards, in shed floors.
Installation
Underground tanks must be specifically designed and manufactured to be installed under load bearing areas such as driveways. Like a swimming pool that is empty underground tanks can rise out of the ground if they are not installed correctly. Eco-smart plumbers are conversant with the installation requirements for underground tanks.
Every 1000L of water = One tonne so it is important to ensure adequate footings are built to bear the weight.
No matter what type of tank is installed it is important to follow the manufacturer’s advice on correct installation.
Overflow discharge
Rainwater tanks in periods of wet weather may reach their full capacity. It is important
this water is discharged as required by council regulations. Generally councils require the water must be discharged to the street drainage system. Contact your local council to check their regulations.
Filtering
To stop litter, leaves and to minimise sediment entering the rainwater tank a number of options should be considered.If you have large trees in around your home you might consider installing gutter guards to stop leaves and tree litter falling into the guttering and blocking them. Alternatively as a minimum you can install leaf diverters on each downpipe. This will prevent leaves and litter from getting into the rainwater tank.
Rain water tanks connected to new homes and extension under the legislation are required by law to have mosquito guards installed. A first flush diverter is at the discretion of the owner. Regardless of mandatory requirements it is recommended that these devices be installed to reduce the need to clean your rainwater tank and to prevent mosquito infestations spreading infection and reducing the quality of outdoor living.
A First Flush diverter is fitted on the inflow side of a rainwater tank. This prevents the first 50 litres of rainwater that contains the silt and any small pieces of litter from entering the tank. This water can then be used on the garden and also assists in prolonging the need to clean out the rainwater tank. Doing these things will help to ensure that only the cleanest water that is possible enters your tank.
If you have concerns about the safety, taste, colour or quality of the rainwater for drinking, it is important to treat the water properly to render it safe. There are three further steps to take after installing leaf guards and a first flush diverter.
Install:
- A washable dirt filter
- A carbon filter to remove chemicals including herbicides and pesticides
- An absolute 0.2 micron ceramic filter or a UV filter to sterilise the water and kill any bacteria
Filtration systems must be serviced regularly to remain effective.
Backflow
It is mandatory for backflow devices to be fitted on rainwater tanks plumbed into homes in South Australia. This is to prevent the possibility of untreated water flowing back into the mains water supply and creating a potential health risk to the community.
Pumps
If you are connecting rainwater to a toilet cistern the Plumbing Industry Association and the manufacturers recommend that you install a pump to ensure the system is under pressure. A pump ensures the cistern refills at the same rate as a toilet connected to the water mains. Gravity fed toilets take some time to refill and it has been found that if the toilet is flushed before it has refilled there is a potential to cause a blocked drain as there is not enough water being used to flush all the contents from the toilet out to the sewer main in the street.
Power supply
Rainwater tanks fitted with an electric pump will require a power point installed on the outside of the house in close proximity to the tank.
Automatic Switching
There are pumps on the market that incorporate a backflow device that automatically switch to mains water when the level in the rain water tank falls below a certain level.
The pump will only work once the tank is full enough to maintain supply so that when it next rains the pump will automatically change back and supply rainwater.
Certificate of Compliance
All sanitary plumbing (water and sewer) in a home must be done by a licensed contracting plumber.
The plumber is required by law to issue a Certificate of Compliance (COC) within seven days of completion. It is important that you receive your copy of the COC as it is proof the work was undertaken by a licensed plumber and is also necessary in claiming any rainwater installation rebates from SA Water. |
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Last Updated ( Thursday, 05 July 2007 )
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