Header Tanks
Tank Away from the Building
Small Kitchen Tank
Maximum Catchment Placement
Roof Gutter Management
First Flush Water Diverter
Dual Water Systems
Dual System Regulations
Underground Tanks
Underground Rainwater Harvesting System for Urban Areas
Header Tanks
A smaller header tank (which does not collect rainwater) can be used to increase pressure in gravity fed systems. The collection tank is at ground level, or buried in the ground as necessary. The outlet of this tank feeds to a small low volume trickle pump, either electric or solar, that keeps the small header tank filled. A floating mercury switch in the header tank turns the trickle pump on or off as required.
To give substantial pressure, the header tank needs to be very high and small so that support costs are kept to a minimum. (One cubic metre of water = 1 Ton).
Tank Away from the Building
For aesthetic or structural reasons, it may be an advantage to position the tank away from the building. The top strainer in the tank must remain below the gutter level with a 4% downpipe slope into the tank.
Note:
It is necessary to put a bend in the top downpipe to exclude the light to prevent algae growing in the water in the pipe after it rains. A mosquito mesh across the downpipe top may also be necessary.
Small Kitchen Tank
A slimline tank is ideal for supplying drinking water, watering indoor plants, cleaning and other household uses.
The tank is positioned alongside the house and water pressure can be increased by elevating the tank.
Maximum Catchment Placement
To maximise the catchment available from a roof, it is ideal to place the tank(s) at the end of the building, allowing the downpipes from both gutters to feed into the tank.
The downpipe capacity must match the overflow capacity. For example, two 90mm downpipes would require two 90mm overflows. Tank overflows can go below the ground and come up again, to meet stormwater run off.
Read the following section regarding Roof Gutter Management for increasing water collection if there are downpipes at the other end of the building.
Roof Gutter Management
If there are two downpipes draining the same gutter section, it is desirable to direct most of the collected water to the downpipe that feeds into the rainwater tank.
Gutter Separator method
A wood or metal separator can be placed ¾ the height of the gutter to direct most of the water flow into the tank downpipe. Gutters must dry out completely after rain and there is a gap beneath the separator so that water does not remain in the gutter. If heavy rain fills the gutter, the excess water will flow over the top of the separator and be drained by the stormwater downpipe.
Downpipe Riser Method
The downpipe riser method allows any excess water to flow over the top of the riser. After rain, water is drained by either a hole in the side of the riser at gutter base level or by a slit in the side. Flat galvanised sheeting can be rolled into a pipe shape leaving a gap for excess drainage. Silicon can be used to prevent the riser being washed away.
The action of any of these should be observed during heavy rain and adjusted accordingly.
Two downpipes can be run into the same tank from either end of the gutter, but there must also be two overflows installed in the tank. The downpipe volume must always equal the tank overflow capacity.
Please check local plumbing regulations for safety.
First Flush Water Diverter
A first flush Water Diverter diverts the water when attached to the tank downpipe, resulting in the first flow of water from the roof passing though the diverter before entering the collection tank.
As the chamber fills, the plastic ball rises to the top and seals the opening. This allows the rainwater to flow into the collection tank. The ball is also necessary to stop the flowing downpipe water sucking dirty water out of the chamber.
At the bottom of the chamber there is an adjustable dripper to drain the dirty water after rain.
There are other types of water diverters but this one is the simplest. You supply your own pipe and set it up to suit your situation.
Dual Water Systems
Dual systems give more flexibility when managing water supply. A dual water system allows you to choose which water source is best for your situation, and swap between the two accordingly.
A smaller header tank (which does not collect rainwater) can be used to increase pressure in gravity fed systems. The collection tank is at ground level, or buried in the ground as necessary. The outlet of this tank feeds to a small low volume trickle pump, either electric or solar, that keeps the small header tank filled. A floating mercury switch in the header tank turns the trickle pump on or off as required.
To give substantial pressure, the header tank needs to be very high and small so that support costs are kept to a minimum. (One cubic metre of water = 1 Ton).
Where there is rainwater and town water available, dual plumbing systems are often used to accommodate the following situations:
Rainwater is only used for the hot water system
Rainwater is only used for drinking water or cold water taps
Rainwater is only supplied to kitchen tap
Rainwater is only supplied to shower and kitchen tap
Tanks used for partial annual supply eg: drinking water in summer.
Council plumbing regulations are sometimes associated with the above arrangements. The set-up must be such that tank water cannot feed back into the Council water supply. It may be a Council requirement that a check valve be installed to prevent this. Check valves cost around $600 with a yearly $100 inspection fee. For environmental reasons, some Councils are combining such valves with the newer type water meters.
However, if you keep each system completely separate, a check valve is not necessary. This means that if hot and cold are different water, you cannot use mixers. (Hot and cold feeding the one tap or a shower rose.) This can be overcome, by placing one-way valves on one or both feed pipes leading to the mixer.
Please check local Council plumbing requirements.
Underground TanksUnderground tanks are a practical and highly efficient system designed to provide pure rainwater for drinking and household use while reducing mains water use - without taking up any space.
Underground Rainwater Harvesting System for Urban Areas
Ideal for urban living, Underground Rainwater Systems collect rainwater from your roof, and stores it underground for your convenience.
With built-in, self cleaning filters, dirt and solid particles are separated from the water, effectively screening and filtering the water ready for consumption.