Rainwater Harvesting

Rain water harvesting is incredibly popular in the UK but it is generally done on a very small scale, using water butts next to gutter down-pipes. Typically 100-200 litre water butts are used because they don't take up much space and they are generally not attractive things to look at. Having said that, you can get water butts that in various styles, shapes and colours, to better blend into their environment. In countries where there is limited rainfall (e.g. Australia), rain water harvesting is a big deal and is taken very seriously. In some more remote places, it is the only source of water for a property. The simple fact is that climate change and population growth are going to place increasing demands on water supplies and increase the cost of water delivered by the mains network.

Rain water harvesting can provide more than 50% of the water required by a typical property and can be used for garden taps, washing machines, toilet cisterns and utility rooms. With large gardens, it is likely to be the only cost effective way to irrigate decorative flower beds and vegetable plots. The collection of rainwater can also reduce surface water around your home and help handle the excessive volumes of water from heavy storms.

Here in Suffolk, we have a very dry climate and hose pipe bans are becoming and annual occurrence. As well as saving you money, rain water harvesting can be the difference between keeping your garden alive through long, dry summers or not. Combined with greywater recycling, it can make a significant difference.

Collection

You can collect rain water in simple open containers but to collect rainwater effectively, you need to collect it falling on large areas. For most people this means the roof of a building, using the gutters to bring the water to one or more collection points. It is also possible to collect water as it runs off fields, patios, driveways and other large ground-level spaces though.

Diversion

Typically, the rain water is diverted towards a storage tank along its way to a main sewer or drainage system and then stored in a tank. Once the tank is full, the excess or overflow is fed back into the sewer. It is vital that you have a reliable way to feed excess water back into the sewerage system before you start diverting in into storage tanks!

On a small scale, it is possible to use diverters installed in existing down-pipes but, these to not always have filters and because of the narrow bore hoses used, these devices are easily clogged by moss and leaves.

Filtering

Rain water really needs to be filtered before it is stored and the filter needs regular maintenance, so must be in an accessible area.

Storage

In the UK, most people use 100-200 litre water butts for storage of harvested rain water but, this is relatively small scale and will not meet the needs of most small gardens over a long hot and dry summer. In order to store sufficient rainwater over the wetter, winter months, you will need to use a much larger tank. Because of their size, these are often installed underground.

Larger tanks can be 'slimline' and located up against walls. Storage capacity can be increased by adding new tanks over time.

If space permits, then really large (>5000 litre) tanks can be used but these can be unsightly and are usually hidden behind screens or buildings.

Larger tanks are often hidden underground.