Reducing consumption

Flushing toilets use about 30 per cent of total household consumption. This can be reduced by changing to a low flush toilet (2-4 litres) or a dual flush cistern. Aerating (spray) taps on basins, sinks and on shower heads make a big impact on consumption. All appliances should have isolating stopcocks so that the whole system does not have to be drained off if one item has a problem. Washing machines and dishwashers vary in the amount of water they consume. This is one of the factors which should influence the choice of white goods.

On average about 200 litres of rainwater fall on the roof of a 100 m2 house each day in the UK. In many homes this is collected in water butts and used to irrigate the garden. However, it has wider uses. There are several proprietary systems for collecting and treating rainwater so that it can be used to flush WCs and for clothes washing machines. An example is the Vortex water harvesting system which serves roof areas up to 200 m2 and 500 m2 respectively. Recycled rainwater must only be sourced from roofs. Storage tanks are either concrete or glass reinforced plastic (GRP). There are controls to ensure that mains water can make good any deficiencies in rainfall. If filtered rainwater is to be used for other domestic purposes, other than drinking, it must be subject to further purification, usually by ultraviolet light. Best use of the filtered rainwater will be made if associated with dual flush WCs. Figure 9.11 shows a typical configuration for rainwater storage.

Figure 9.11

Rainwater storage system layout (courtesy of Construction Resources)

Typical domestic rainwater installation with storage tank in the ground and a pressure pump in the tank

1 Vortex fine filter 8 Automatic switch and

2 inflow smoothing filter ballvalve

3 Tank 9 Overflow trap

4 Floating fine suction filter 10 Installation controls

5 Suction hose 11 Magnetic valve

6 Multigo pressure pump 12 Open inflow for drinking

7 Pressure hose water feed

13 Backpressure flaps

Typical domestic rainwater installation with storage tank in the ground and a pressure pump in the tank

Figure 9.11

Rainwater storage system layout (courtesy of Construction Resources)

Floating Roof Tank Construction

It is possible to go a stage further and use rainwater for drinking, but this requires even more rigorous filtration, as employed, for example, in the the Vales' Southwell autonomous house (p. 77). The water from the roof passes through a sand filter in a conservatory. From here it is pumped to storage tanks in the loft and from there through a ceramic/carbon filter to the taps. As an act of faith in the English weather there is no mains backup facility.

A variation on the water recycling strategy is to reuse grey water from wash basins, showers and baths. If waste water from a washing machine is included, then virtually all the waste water can be used to meet the needs of flushing toilets. Again there are systems on the market which serve this function, including water storage.

The Hockerton Housing Project has all these facilities and more because it uses rainwater collected from its conservatory roofs for drinking purposes. The water is stored in 25 000 litre underground tanks where particles have time to settle to the bottom. The water is treated first by passing it through a 5 micron filter to remove remaining particles. Then it is sent through a carbon filter to remove dissolved chemicals. Lastly it is subjected to ultraviolet light to kill bacteria and viruses. The author can vouch for its purity! For the average home this may well be a step too far, but those who feel inspired by this possibility should contact the Hockerton Housing Project at

For the really dedicated there is the composting toilet which eliminates the need for water and drainage. In Europe a popular version is the Clivus Multrum from Sweden. It is a two-storey appliance in that there has to be a composting chamber usually on the floor below the toilet basin. Fan-assisted ducted air ensures an odourless aerobic decomposition process. The by-product from the composting chamber is a rich fertiliser.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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