Thu 3 Jul 2008
Water, water everywhere
Reducing water consumption is no longer up to the individual alone - housebuilders need systems in place to ensure that their buyers use as little of the clear stuff as possible. Roger Hunt explains.Water consumption in the UK currently stands at around 150 litres per person, per day, a figure that has been rising by one per cent a year since 1930. This is despite the fact that, according to the NGO Waterwise, the UK has less available water per person than most other European countries; London is drier than Istanbul while the South East of England has less water available per person than the Sudan and Syria.
Clearly present water consumption is not sustainable. The Code for Sustainable Homes lists a mandatory level of 120 litres per person per day to achieve levels 1 and 2, and just 80 litres per day to achieve levels 5 and 6 - a figure that gains five credits.
The Code's aim is: "To reduce the consumption of potable water in the home from all sources, including borehole well water, through the use of water efficient fittings, appliances and water recycling systems." But this is not the only mention of water; surface water runoff is another aspect to be considered. The aim here is: "To design housing developments which avoid, reduce and delay the discharge of rainfall to public sewers and watercourses. This will protect watercourses and reduce the risk of localised flooding, pollution and other environmental damage."
For the housebuilder this means considering a gamut of water related measures ranging from dual flush WCs and aerated taps and shower heads to greywater recycling, rainwater harvesting and runoff attenuation through green roofs and Sustainable Urban Drainage Systems (SUDS). The simplest and cheapest measures to implement are those relating to fittings and appliances such as washing machines and dishwashers.
In a bid to make product identification and selection easier, the Bathroom Manufacturers Association (BMA) launched its Water Efficient Product Labelling Scheme earlier this year. This industry-led, voluntary scheme is open to all companies producing and selling water efficient products for UK markets. Currently covered are WC suites, independent flushing cisterns, taps and combination tap assemblies, shower controls and baths.
Yvonne Orgill, BMA chief executive, explains that the scheme is going to be expanded. "It will include a lot more products to allow the housebuilder to meet the levels of the Code for Sustainable Homes and they will be able to source through brand name, volume or flow rate, third party certification and so on. We are also going to start a campaign to educate consumers.
"Research shows that three years ago, unless you were an eco warrior, water efficiency wasn't even on people's list of requirements when purchasing bathroom products; now it is number four behind price, design and brand."
Improved design of plumbing layouts within homes, with a reduction of 'dead legs' where water has to be run to waste before it gets hot, is something else that housebuilders need to consider. But, to achieve greater water savings, they need to look to recycling water used within the home and rainwater harvesting; both of which are becoming a realistic, although not necessarily cheap, proposition.
"As far as consumers are concerned, greywater recycling does exactly what it says on the tin," explains Alan Penny, business development director for Greenworks, Jewson's sister brand, which markets both greywater and rainwater harvesting systems. "Greywater is recycled shower and bath water that is used for toilet flushing. Importantly you can't override the system. The issue if you use aerated taps or a lower delivery shower head within properties is that obviously consumers can get around that if they don't like it by changing the product."
One of the points against greywater is that it is, as its name suggests, discoloured. Penny counters this with the argument that the threat of a restricted supply is a greater negative. "Culturally we have to embrace this and my view is that legislation will force us down the greywater route."
Greenworks' solution to greywater recycling is the Ecoplay system which can reduce the quantity of fresh water used for toilet flushing by up to 30 per cent. Similar in size to a traditional concealed in-wall cistern, the unit is claimed to be virtually maintenance-free. It collects water from the bath and shower in a cleaning tank where light materials, such as foam and hairs, are skimmed from the surface while heavier materials, such as dirt or sand, sink to the bottom. The remaining 'clean' water is then transferred to a storage tank from where it can be gravity-fed, or pumped on demand, to the toilets in the property.
If the toilets are not flushed within 24 hours after a period of regular use - if for example the property is temporarily unoccupied - the system detects this and purges the retained recycled water to waste. This serves to clean the system and, once empty, the unit then imports a minimum of mains water sufficient to operate the toilets thereby maximising efficiency.
A more radical approach, but one that would perhaps become cost effective for housebuilders if UK water companies were to adopt it, is to be found in Australia where water recycling is being undertaken on a development wide basis with the water treated and stored centrally. The largest residential water recycling scheme is in Sydney's Rouse Hill area where more than 17,000 homes are now using 1.9 billion litres of recycled water each year for flushing toilets, watering gardens, washing cars and other outdoor uses.
Sydney Water provides homes in the area with two water supplies - recycled water and drinking water. The recycled water is treated to a very high standard but the water taps, pipes and plumbing are coloured purple to ensure that recycled water is not confused with drinking water. On average the scheme has reduced demand for drinking water by about 40 per cent and eventually the scheme will serve 35,000 homes.While greywater recycling has many fans, the concept of rainwater harvesting is probably more easily understood by consumers. According to Terry Nash, company secretary of the UK Rainwater Harvesting Association (UKRHA), the UK market for rainwater harvesting has increased by around 1,000 per cent in the last four years. "But this has been from a very low base and we are still only probably a hundredth of the size of the market in Germany."
At its simplest rainwater harvesting is a water butt connected to a gutter downpipe. More sophisticated systems allow the water to be used not only to water gardens but flush toilets and even feed the washing machine through a separate pipe network. However, the stored rainwater is not suitable for drinking.
A typical domestic rainwater harvesting system provides around 50 per cent of a household's total consumption but the amount of water saved depends on the size of the catchment area - usually the roof of the building - and the amount of rainfall.
The tanks used have filters that remove all debris and particles from the water so that the water remains clear. When there is insufficient water in the storage tank the system automatically draws water from the mains.
"A well designed rainwater harvesting system will be designed around a number of parameters: how much water the building will collect, how much the occupants of the building will use and how long the water is going to stay in the tank," explains Nash.
The environmental impact of both greywater recycling and rainwater harvesting includes carbon footprint savings as the water only has to be transported over a short distance rather than from the nearest water-works. There is also a saving in the energy and chemicals used in bringing water destined for toilet-flushing up to drinking water standard.
Rainwater harvesting may form an integral part of a SUDS strategy. Green roofs can be another component although, to a degree, green roofs and rainwater harvesting systems work against one another because of the effectiveness of a green roof in limiting runoff so the systems are rarely used together.
SUDS are increasingly a prerequisite of any development and wrapped crates or other cellular systems with a high void ratio are commonly used to create below ground soakaways or storage structures. They are just one of the systems discussed in the 'Site handbook for the construction of SUDS' published by CIRIA. It emphasises that "the philosophy of SUDS is to replicate as closely as possible the natural drainage from a site before development".
This is particularly relevant where areas of hard landscaping such as roads, pavements and car parking are introduced so permeable paving is increasingly used as a way of controlling storm water. For example, Wienerberger's new Aquata natural clay paving allows water to pass through its surface to be filtered, cleaned and stored within the voids in the component layers beneath. Alternatively it can be laid over a cellular system that will attenuate the volume of water entering the drainage system or alternatively harvest it for use within the development's homes.
Posted by Roger Hunt
in Alan Penny, Bathroom Manufacturers Association, Greenworks, Jewson, Sustainability, Terry Nash, UK Rainwater Harvesting Association, Yvonne Orgill on Thu 3 Jul 2008