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Water Conservation

see also Rainwater harvesting

This tends to be something of a regional issue but certainly in the South East, it is becoming a major concern with planning permission being refused in some areas due to a lack of water.

A huge nonsense is the amount of water which is purified to drinking quality standard and then used to flush toilets. About a third of the water we use is wasted in this way. The same is true for washing cars or watering the garden.

There is a massive political issue around water supply. One of the conditions of the privatisation of water was that the water companies are legally obliged to supply water as required. This drives them to do three things

  • build more reservoirs to cover periods of low rainfall (now this is difficult because there tends to be a lot of local opposition from people who don’t want to see their homes submerged in a new reservoir)
  • raid (or mine) rivers to get more water. (this depletes rivers, usually when they are most at risk in summer; fish and wildlife tend to suffer.)
  • manage demand by installing meters and upping the price of water.

the dilemma is that while building regulations are causing better water saving design, a growing population is busy using more water (for things like power showers and garden watering)

saving water

The Waterwise web site covers issues about how much water we use and where savings are to be made.

Depending on how important you feel the subject to be, there are several approaches:

  • Do all you can to minimise water use.
  • Use composting toilets to save 30% of all the water
  • An easy option is to install tanks to harvest and store rainwater for garden irrigation
  • Ditto but use the rainwater for everything except where wholesome water is required. (backed up by mains). The UK Rainwater Harvesting Association has been formed recently to promote this area. You are very unlikely to be able to collect enough water for all your needs but toilet flushing and washing machines are good uses which need a minimum of water treatment.
  • Install a system for reusing bath and shower water for toilet flushing such as the Ecoplay product. More products on the Waterwise web site.
  • Install low flush toilets such as the Swedish Ifo and use water saving cisterns and appliances. It is worth checking that the flush mechanism on low flush toilets is intuitive. Some of them are quite unclear about which is the high and which the low flush.

Note that water storage tanks and cisterns buried below ground have the potential problem of lifting (effectively floating) up out of the ground if the condition arises that they are empty (and therefore light in weight) and the surrounding water table is high. They may need weighting down. Check the suppliers literature

recycling grey water

rooftop grey water recycling by WWUK

grey water is best used for either flushing toilets (after being suitably treated) or for watering the garden/washing the car.

Water Works UK Ltd have developed their green rooftop ‘Grow’ technology for recycling grey water into green water (water suitable for flushing toilets, garden watering, car washing etc.)

A recent report by the Environment Agency, Energy and carbon implications of rainwater harvesting and greywater recycling looks into the carbon footprint of water recycling and shows how there is an increase in carbon use, not only because of the energy to make tanks etc but also how the pumping energy costs are higher than with mains water. The recommendations are partly about gaining a better understanding of when harvesting is beneficial and this has to take into account a large number of factors such as local rainfall levels, density of population and water distribution networks.

disposing of grey water

Reed bed water purification systems are often used for tertiary treatment when a house is not connected to the main sewerage system and water effluent needs cleaning up before it soaks into the ground or enters a watercourse. This is quite common for the effluent from septic tanks, package treatment plants or secondary treatment systems.The reed bed is usually an area of medium such as gravel contained in a waterproof membrane. As the effluent seeps through the medium, bacteria in the soil break down the contaminants in the water (such as soaps, detergents carbohydrates etc.) and they bio-degrade leaving a much improved effluent. There are various configurations of reed beds such as vertical flow, horizontal flow, and combinations of the two which may be in sequence. It is usually necessary to obtain expert advice on the design of reed beds. Short courses are sometimes run by CAT. see  CAT’s website

Much development of constructed wetlands has been pioneered in Germany. This shows a scheme of about 100 flats in Kreutzberg, Berlin, built around a beautiful reed bed treatment system for grey water. The cleaned-up water is then used for flushing toilets.

A particularly interesting use of reed beds , from the ecological point of view, is in conjunction with composting toilets . If the human waste is broken down in a composting toilet then the reed bed only has to handle the grey waste water such as the water from baths sinks showers etc. so the design can be simpler. With this configuration, all the waste products can be considered as nutrients and fertilizers which get returned to the local land rather than being dumped into rivers after they have gone through the local sewage plant. Although sewage treatment plants have been greatly improved over the last decade or so (with the consequent improvement of river water quality) there is still a considerable degree of contamination , especially when localised flooding occurs.

The Environment Agency also deal with registration of Septic tanks and small sewage treatment plants


The Building Regulations, part P now stipulates that with new houses, calculations are provided to the BCB showing how much water the house is expected to use and it gives limits for various house types. The calculator is here

There are various initiatives afoot to implement further water saving standards :

The AECB have gone for an approach which can basically be implemented by being careful about the way normal plumbing and water outlets are designed. It doesn’t require any different technology and is aimed at achieving what people consider acceptable. It specifies the maximum volumes and flow rates for baths, showers, sinks etc and limits the dead legs allowed on the pipework. It comes as the Carbonlite Water Standard with two levels – Good Practice and Best Practice.

The Code for Sustainable Homes goes a good way further than the AECB in the way that it covers the collection of rainwater and recycling of grey water. It sets certain limits on things like hot tubs and swimming pools which use a lot of water and it covers white goods. The use of water for watering gardens is taken into consideration. There is a water calculator which is part of the assessment procedure.

water saving and SUDS

It has been described as ‘a marriage made in heaven’. Carried out correctly, saving water can work very well with SUDS. SUDS can be implemented using attenuation tanks which hold back storm water and allow it be released slowly. The same tanks can store rain water for the purpose of toilet flushing, washing machines, car washing and garden watering (all uses where wholesome water is not required). There are lots of companies now offering such tanks along with size calculations. See the UK Rainwater Harvesting Association Briefing Paper.


Greywater Action

The Humanure Handbook

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