Harvesting the rain seems like a no-brainer. But is it too expensive? And could you live with an AstroTurf lawn?
Rainwater harvesting systems (RHS) – as you might expect from the name – harvest the rainwater that has fallen freely from the sky, typically onto the roof of your home. In contrast to the humble water butt, which typically captures about 200 litres of rainwater, a rainwater harvesting tank can easily filter and store up to 6,500 litres of clean water.
What’s more, while these systems have traditionally been used to water the garden, new technology means an RHS can now be plumbed into your home’s existing pipework and the rainwater used to flush toilets and wash clothes. This means that you could reduce your water consumption by as much as 40%, according to the Rainwater Harvesting Association, which – if you switch to a water meter – will lower your water bills as well.
Rainwater harvesting v greywater recycling
The amount of water you save with one of these systems is lower than the 50% savings that you can potentially get with a greywater recycling system because rainwater supply is less certain. “You will need to be able to rely on your mains water system as a backup during periods where there is little rainfall”, says Derek Hunt, from Rainharvesting Systems.
However, unlike a greywater recycling system, RHS requires little specialist maintenance and the rainwater you harvest – as it has never been used to wash food or the human body – is likely to contain far less bacteria and contaminants than greywater. This can make RHS a cheaper and more environmentally-friendly choice for many homeowners, say the proponents of these schemes. So what’s out there and how do they work?
Rainwater harvesting systems that plumb into your home
If you’re looking for an RHS that will allow you to use the water to flush the toilet, wash clothes in the washing machine and even clean the house, as well as water the garden, and you’re prepared to excavate your garden, one of your best options is a Graf system, says Phil Barnard, from rainwater harvesting systems supplier Chandlers Building Supplies. “The tank has a self-cleaning filter that you only need to check on it once a year. It costs about £2,500 for a 2,700 litre tank, and a buried tank isn’t affected by heat change or light, so the water doesn’t go green and smelly.”
You should expect to pay no more than £1,000 for installation by a competent plumber or builder, and according to Chandlers no crane is required. The size of tank you should get varies according how much rainfall you usually get, and what you are planning to use the rainwater for.
You’ll need energy to pump the water up out of the tank and around the house: this costs about 10p a week for a three-bedroom house using rainwater for ta toilet, washing machine and the garden, according to the RHA – but it does make the system as a whole less environmentally friendly.
The alternative, the Ifore rainwater harvesting system, is a gravity fed and installed in the loft. It collects water direct from the roof by substituting a drain for four roof panels and requires no electricity whatsoever, and costs £1,700 in total to buy and install.”
It’s a very simple system and because of its simplicity it means the likes of a competent DIY-er can fit it themselves,” says designer Clive Hall. The internal fitting means that the size of the tank is limited to 455 litres – so in the summer, if it doesn’t rain for a long period, you may have to rely on your mains water system (which will automatically come into play in this situation).
The system is designed to be retro-fitted to existing homes and the maintenance required is low, although Hall does recommend putting a chlorine tablet in the tank before you go on holiday as the tank can start to smell when the water inside is stagnant. The benefits of the system, however, can be huge: “You’ll reduce your water usage by 35% to 40%,” says Hall. “In a rainy season, you can save as much as 55%.”
Rainwater harvesting systems that water your garden
While through most of the year, outdoor water use accounts for just 7% of the total water we use, in the summer this rises dramatically to over 50% at peak times, according toWaterwise.
One rather unusual option would be follow the lead of former architectural technologist Jonathan McGee. His home looks, from the outside, like any other terraced house in a quiet corner of north Leeds. But this particular property, with its blooming flower beds, manicured front lawn and Victorian replica hand pump, is actually at the heart of a new revolution in rainwater harvesting technology. Because beneath the surface of that beautiful looking lawn is an underground tank full of self-cleaning rainwater – and the grass isn’t grass, either: it’s effectively a water filter, made from AstroTurf.
“Our garden is very small, and it used to get waterlogged and overgrown, because I couldn’t bring myself to buy a lawnmower just to mow a section of grass measuring 16 sq ft,” says the property’s owner, Jonathan McGee. “My wife, Jessica, and I wanted a nice, pretty garden that would allow us to water our flower beds without dragging a hosepipe round from the back or carrying water buckets through the front. So I started googling AstroTurf lawns and rainwater harvesting systems. ”
The solution that he discovered is an innovative type of rainwater harvesting tank, developed by AstroTurf supplier Bradleys Surfacing Systems, that now sits just 10cm before the surface of McGee’s AstroTurf lawn. Unlike a traditional rainwater harvesting system that, because it captures rainwater from the roof, needs to be plumbed into the guttering and downpipes, the Bradleys system captures rainwater from the lawn itself, and the blades of “grass” act as filters to trap the dirt.
It cost McGee £3,600 in total, which included the VAT, installation and the AstroTurf, and McGee says it has already proved cost-effective. “We’ve been watering the garden two or even three times a day in the summer months; we’ve got blueberries, blackcurrants and roses, and at this time of year, without regular watering, they’d just die. But the only water we’ve used to water the garden is the rainwater we’ve harvested, so it’s worked out very well in terms of our water usage – better than we had anticipated.”
The system is different from the traditional rainwater harvesting system, which requires a deep excavation to accommodate a large, 2,700-litre water storage tank. These large tanks are often impossible to place in a front garden where there are existing services in and out of the house, says the designer of the AstroTurf system, Tom Bradley. “By contrast, our unique system has a depth of only 100mm but can be as large as the area of AstroTurf required.”
This does reduce the amount of rainwater you can harvest, however. Bradley says the average tank he sells measures nine sq m, but will only store around 500 litres of water at a time. Yet, since it includes the cost of the AstroTurf, the system is almost five times more expensive than much bigger rainwater harvesting systems that exist solely to water the garden.
“You can get above-ground tanks that hold 1,200 litres of rainwater for £750,” says Hunt. “That’s at least six times the size of a normal water butt and for that price, you can even get a pump that will power a sprinkler with filtered rainwater.”
If you don’t want a large tank to be visible in your garden, however, you should expect to pay at least £250 more for an underground tank, plus you’ll have to excavate the ground, which can add another few hundred pounds.
The Bradleys system is still likely to work out more expensive, however, and could also be criticised from the environmental perspective. “AstroTurf is not a very good habitat for insects and biodiversity and you may need to use water to clean it,” says Jacob Tompkins from Waterwise.
McGee is very happy with his decision however: “I constantly recommend our system to the neighbours on our street. I wanted an AstroTurf lawn anyway, and in those circumstances I think everyone should do it.”
- Greywater systems: can they reduce your water footprint?
- Composting toilets: a growing movement in green disposal
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