Water Recovery Systems: A Self Builder's Guide

Harvesting rainwater or recycling what you've used in the shower can cut your use of mains water. Discover how.

By Sarah Warwick

Why Save & Re-Use Water?

Demand for water is rising, and in south east England there's less available per person than in many Mediterranean countries, according to the Environment Agency. Using the rain that will fall on the roof of your newly built home, and re-using domestic water can mean savings on metered water. Water recovery could also help you meet the requirements regarding water consumption in the building regulations.

How Can Water Be Re-Used?

There are two ways you can re-use water. First by harvesting rainwater and secondly, by using so-called grey water from showers, baths and basins. Both sources can provide water to flush toilets, and possibly to use in the washing machine and on the garden. The benefit of grey water systems is, of course, that you know your home will regularly produce it - rainfall is less reliable. You can cut down your mains water use by around third by flushing the toilet with rain or grey water.

Is It Energy Efficient?

Be aware that grey water systems do use energy, particularly to pump water, and that generally treating and supplying grey water takes more energy per litre than doing the same to a litre of mains water. It is more cost effective to save water rather than install a rainwater or grey water system, says the Environment Agency.

How To Use Rainwater

Collecting and re-using rainwater can be as basic as fitting a water butt or as sophisticated as installing a rainwater harvesting system. These systems can be incorporated in a sustainable drainage system, which reduces flood risk, something that in England is required to be considered during the planning process.

You'll need to take into account how much rain falls where you live, and what area you have available to collect it. The arrangement of downpipes, the type of roof, and even the heaviness of rainfall will affect how much rain is captured.

The water collected on the roof goes through a filter, and is then stored in a tank, which needs to be sized taking into account the cost of the tank itself - often the most expensive part of the system - and how much water you will be storing. The tank is most often sunk in the garden.

Once collected, the water can be pumped to where it's needed; fed by gravity; or pumped to an elevated cistern then fed by gravity. It travels through separate pipes as it's not potable water.

How To Recycle Grey Water

To recycle grey water you will need a system consisting of a tank, pump, distribution system and some type of treatment to prevent odours, poor water quality and the growth of harmful bacteria in the water.

If grey water is to be re-used after a short time, it can be treated quite simply with the system releasing the water if it's stored for too long. This type of system is cheaper, and you won't need extra plumbing.

For longer storage, there are biological systems where bacteria are used to decontaminate the waste water. This might employ the use of a pump or plants, such as reeds. Reed beds need maintenance, and suitable space in your garden.

Alternatively, some systems use biological and physical treatment - and need to be fitted in a garage or basement. This produces a high level of water quality, meaning it could be used for washing the car, too. These systems are more expensive.

You can also get systems that combine rainwater harvesting and grey water recycling. The Environment Agency recommends that you consider these only if one or other system on its own wouldn’t meet your home's needs. Additionally, the overflow from this type of system needs to go to the foul sewer because it contains grey water.

A grey water system should be chosen according to the way in which you use water in your home. If the whole family showers every morning, then goes out to work, you won't need the water for flushing the toilets during the day, so you'd have a surplus and wouldn't actually save much water.

What Will It Cost?

You should budget around £3,000 to buy and install a grey water system, according to the Environment Agency. A rainwater harvesting system costs from around £2,500, depending on tank size, it estimates. Whether you are installing a rainwater harvesting or grey water recycling system, call in professionals as there are serious health considerations involved in storing and re-using water in your home, as well as Water Regulations that must be followed regarding mains water back-up.