There is perhaps no better time to think about the practicalities of home rainwater harvesting than during your typical British summer. After all, the British summer has two states, which are parched, sun-scorched drought and torrential, flood-inducing rainfall. There is little middle ground.
But playing the wet off against the dry cannot just provide you with a way to water your garden when everyone else’s lawn is reduced to tinder-dry straw, it can save you plenty of money too. Modern rainwater harvesting systems go beyond a water butt in the garden or a collection of buckets on the shed roof. They can feed water back into your home supply for use in your outside tap, toilet or even your washing machine, providing you with free, clean water that is good for the environment and your bank balance.
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You may even find yourself doing a rain dance in your garden, as using rainwater in this way can cut anything from 30% to 50% (possibly more in a rainy year) from your water bill. But before you start celebrating you should realise that installing an efficient rainwater harvesting system can be both an expensive and disruptive job.
As you might expect, the system that can harvest the most water is the best. But that does rely on you having the capacity to install it and the desire to go through having your garden dug up first. If you can face the disruption then you will find that the results are unobtrusive and very efficient.
You choose a size of tank based upon the size of your garden and then the tank will collect water as it falls on the garden. The larger the surface area, the more rain you will collect. As it falls, the water passes through a filter before entering the tank and again before being pumped into your home via a low-energy electric pump.
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These tanks generally need little cleaning or maintenance, as the lack of light below ground means that algae growth is less likely and the tank will not start to smell. This can be a problem with the more common roof-mounted rainwater harvesting systems, which collect rainwater as it hits your tiles, filtering it into a tank via a small area of roof that has been removed. For example, if you go away and leave water in the tank it can start to smell after a week of being left unused.
Rooftop system tanks are generally a lot smaller than the type you have beneath your lawn, as these have to fit in your loft or roof space. Loft tanks usually hold less than 500 litres, whereas a standard garden tank will hold ten times as much rainwater. The beauty of the rooftop system is that it can feed your water into your toilet or washing machine via a gravity feed and does not need a pump. The downside is that there is a very small chance of a leak, which can mean an expensive redecorating job. You can also use a system that drains water from the roof to a ground tank but this will prove to be more costly.
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When it comes to costs, a roof-mounted system will cost around £1,500 for hardware and installation, whereas an underground system will usually cost upwards of £3,000 fully fitted. So you will have to weigh up factors such as disruption and cost against a higher water yield and reduced water bills. Always check your water usage before you embark on such a project, as you don’t want to simply go for the maximum yield and tank size if you are never going to use that amount of water on washing clothes, using the garden hose or flushing the toilet.
Of course, those who don’t want to commit to the cost just yet can still use the time-tested method of collecting rainwater in a water butt, which you can set up to collect water from a roof or garage downpipe.
The savings from installing a rainwater harvesting system may see you looking out of the window and urging a storm to roll in. But please spare a thought for those of us who don’t have rainwater harvesting systems installed as yet and may be on the way to the beach.