Rainwater Harvesting
In light of the current introduction of water charges, rainwater harvesting has come back in fashion.
The benefits are reduced water charges for those on a metered supply, and reduced pump running costs for those with their own supply. It is obviously good for the environment too.
A gravity supply system is the easiest and cheapest to set up, and it works without the need of a pump. If in your system, the tank is lower than the the troughs that you aim to supply with water, you will need to install a pump.
Of course you will have to have a back up supply of water available for spells of dry weather, when little or no rainfall occurs.
How to set up a gravity feed Rainwater Harvesting System
1) Identify a suitable location for your storage tank.
- It should be close to the downpipe of an existing shed if possible in order to capture the rainwater with minimal piping adjustments required.
2) Identify a suitable tank.
- The obviously the bigger the tank the better as it will give you more storage for dry spells.
- If possible the outlet from the tank should be 25mm to 50mm (1" to 2") above the base of the tank to allow any grit or other debris from entering your water system.
- There should also be an outlet from the tank at the very bottom for occasional cleaning and removal of grit.
- It is possible to use a number of IBC tanks together if required.
3) Establish if the storage tank needs to be elevated.
- If you have insufficient head flowing to the troughs being supplied, it will be necessary to construct some sort of elevated platform for installing the tanks on.
- The platform needs to be lower than your rainwater gutter, but higher than your highest trough.
- The platform must be a sufficient strength for the weight of the full tanks. Remember that 1000 litres of water weighs 1 tonne. Don't forget to consider the weight of the tanks themselves.
- The platform should be designed so that children cannot access it.
4) Install the tank.
- Make sure it is secured in place to ensure that it cannot slip or roll.
- If necessary it may need to be secured in case it's blown away during high winds when empty.
- Plumb the outlet to the troughs being supplied.
- Fit a ballcock and stop valve to the top of the tank so that you can fill it from the main supply during dry weather. Connect this to the mains, but keep the valve shut apart from occasions when you need to fill the tank from the mains.
5) Plumb the downpipe from the roof into the tank.
- A filter to catch leaves and other debris should be installed to prevent them from accumulating in the tank.
- A suitable sized overflow from the tank needs to be included to take any excess rainwater to the nearest gully or drain.
6) Keep an eye on the operation of the tank as you carry out your day to day chores.
- The tank will need to be cleaned out occasionally to prevent too much grit from building up.
- If the water in the tank is not being used for a spell, it may become stagnant. Do not allow this to occur.
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