Water

Water conservation

Provided by Robert Barker: co-director of Baca Architects

 

What, Why, When, How, Extras

 

What is it?

Water conservation is a design measure to establish more efficient use of water in order to reduce loss, use and waste. The intention is to reduce water demand and this can take several forms: water recycling, water saving devices and water storage areas. In households and businesses this involves water saving devices, water efficient equipment and recycling. In industry and particularly agriculture this can involve a change in production methods, such as drip irrigation over flood irrigation, wet silage based food products and improved rainwater harvesting and use.

 

Why use it?

Water is a precious natural resource and its sustainable management is essential to protect the water environment and to meet current and future demand. The average person in London uses 156 litres per day, 50% more water than we did in 1980. In London (mirrored by the rest of the UK) the population has grown by approximately 10% in the same period. Mean average rainfall is predicted to fall in the east of the country, affecting the highly populated southeast. We cannot sustain water consumption at this level nor rising consumption, therefore, we need to reduce consumption and conserve more water. Water supply is likely to rise in cost, therefore introducing water saving devices can also save costs on utility bills.

 

When to use it?

Water conservation measures should be used in the early design of all new buildings to deal with growing demand and ever growing shortages whether it is for residential, industrial, agricultural or commercial use. In existing buildings it is still possible to reduce water consumption through new fittings and fixtures such as low/dual flush toilets, aerated taps. Grey water recycling is far more expensive to retrofit than from the outset but and rainwater harvesting can be installed even if only to irrigate the garden.

 

How to use it?

Key Points:

 

  • Water meters have been shown to reduce household water use by 5% to 15%.
  • Water meters also help to monitor the effectiveness of water saving devices.
  • Composting toilets require virtually no water.
  • Separating water uses such as drinking/flushing for potable/recycled water may require separate infrastructure.
  • Could water used to keep dust levels down on construction sites be recycled or can prefabrication minimise this wastage?

 

Design Procedure:

 

  • Step 1: Establish whether water usage can be reduced by lifestyle or business design changes such as composting toilets, showers instead of baths, and less water intensive facilities (such as reduced wash down areas, passive cooling of data centers).
  • Step 2: Identify appropriate water saving devices such as low flow taps, electronic sensor taps, low flush toilets, time restricted showers (widely used in Australia), and efficient washing machines. These flow rates can be used to calculate the overall water use, more accurately than generic per person guidelines. The Code for Sustainable Homes provides a water calculator. (see fig 1.)
  • Step 3: Identify the capacity for rainwater harvesting (see rainwater harvesting) to identify how much can be provided without using mains supply potable water. Offices typically use less than a third of the water per person per day of households and are only operational five days a week. Therefore it may be possible to provide all of the water supply from rainwater harvesting or recycling. (see fig 2.)
  • Step 4: Identify the water usage in the building, whether it has to be potable (drinkable) or can it be re-used elsewhere?
  • Step 5: Identify if it is possible to recycle wastewater. It is possible to treat all wastewater to drinking standard though it is more common to recycle grey water (from showers, washing machines etc) and use for flushing toilets. See wastewater management. (see fig 3.)

 

 

Low water fittings

Fig 1. Low water use appliances (dual flush wc, aerator tap, mist sprinkler). (Click image to enlarge)

Water use in buildings

Fig 2. Micro-component household water use in buildings (2007). (Click image to enlarge)

Compact grey water recycling

Fig 3. Compact grey water recycling. (Click image to enlarge)

 

Related strategies

Night ventilation Rainwater catchment SUDS

 

Take this further

Case studies