It is our experience that many people think rainwater harvesting systems are more expensive than they actually are. Basic Garden only systems with above ground tanks, automatic submersible pumps and rainwater filters can cost under £500, and full Domestic systems with underground tanks and automatic mains water backup systems start from around £1000 for a small property. Therefore, it doesn’t have to cost a fortune to add this technology to your property. Of course, there are systems with added ‘bells and whistles’ which will cost that bit more for those users who want the best of the best, however if you’re keen to know what options there are to add rainwater harvesting to your property on a lower budget then here are some ideas.
Use an above ground tank
The costly part of rainwater harvesting installations is burying the tank underground. Although the water is best kept in an underground tank, due to the temperature all year round being consistent and not allowing the water to get too warm or too cold and freeze, however systems can be achieved using above ground tanks as long as the location of the tank is considered. Ideally keep the tank somewhere out of direct sunlight to avoid it getting too hot in the summertime and consider emptying the tank to at least half-way if there is a risk of frost during the winter months.
Use a simple downpipe filter or larger filter if collecting from several downpipes, above the above ground tank.
Downpipe filters can cost considerably less than the typical in-tank filter which is supplied with most complete rainwater harvesting system packages that are suitable for roof areas of up to 350m2. If you can connect either one or two downpipes into the above ground tank
then add a downpipe filter to each one, which can be less than £20 each, to make sure that the water collected inside the tank is clear of any leaves or debris that runs off the roof.
Once you’ve got your filtered water inside an above ground tank, you need a submersible pump which can pump the water from this tank directly to your outside tap and/or a toilet inside your property. Depending on how much roof area you have managed to collect from and route into your tank, you may be able to connect the supply of harvested rainwater to more places but the minimum you should achieve from just one downpipe off one side or even one small area of roof will be your outside tap and if you have one, a downstairs WC.
Keep the pipework as simple as possible, ideally fitting just one pipe from the submersible pump inside the tank and connecting this to the one or two outlets. The all you need is a form of mains water backup to top-up the water level inside the tank in dry periods when you’re not collecting any rainwater. For this there are several options too. To automate the process you will want a float switch or level sensor of some sort, connected to a solenoid valve which will control the opening and closing of the mains water pipe to fill the tank. You will need to incorporate a tun-dish to ensure the airgap between the rainwater tank and the mains water, so that you prevent any risk of cross-contamination into the mains water network, and this will need to be fitted in a location that enables the mains water to fill the above ground tank via gravity supply (meaning it has to be higher than the top of the above ground tank). It can be outside, as long as it is insulated to protect it against frost.
Of course, if you want to keep the budget really low, it may also be possible to do without the mains water top-up. If you’re only supplying an outside tap and one of several WCs at your property with the harvested rainwater, then can you do without the mains water top-up function? You use the rainwater when it’s available and you use the other facilities in your home which are connected to the mains water when the rainwater tank is empty. It all depends on what you want to spend, how convenient you want the system to be and how automated you want to make the process. The key here is to realise that rainwater can be recycled and put to good use for a value much less than the thousands of pounds that can and has been spent on many domestic rainwater harvesting systems. If you have a budget in mind and want to see what you can achieve, it is well worth talking to some suppliers and getting some advice to find out what will work at your property. Whether you have room for one large above ground tank, or several smaller, thinner tanks linked together to create a higher storage volume, there is something that will work for most properties and where there is a desire to save water, there is certainly a way to do it on a budget.