BSEE
INDUSTRY COMMENT Public Health Water System Design
In the UK, water supply quality is controlled by UK and Scottish Acts of Parliament. While parties such as OFWAT and the Water Industry Commission for Scotland have enforcement responsibility, it is water suppliers which enforce the Water Fittings Regulations and bylaws.
he Health & Safety Executive also publishes guidance and codes of practice relating to domestic water services, which have special legal status. These standards and regulations set down detailed national requirements for the design, installation, operation and maintenance of plumbing systems, water fittings and water- using appliances. They are designed to prevent misuse, waste, undue consumption or erroneous measurement of water, and to prevent drinking water contamination. However, no two water-system design engineering projects are ever the same. Often subtle differences between two similar projects can bring significant issues and outcomes in terms of plant and pipe sizing, and the resulting system’s performance. Best practice advice when evaluating efficient measures for inclusion in water supply systems would therefore be to maintain focus on the health and wellbeing of end-users, and do not let efficiency lead to compromises in system performance or contamination of the water system. When using mains water, specifying efficient fixtures, appliances and water-heating systems can reduce a building’s environmental impact. Filtered rainwater and greywater (from showers, basins and baths) can also be recycled to meet demand for non-potable water use, such as gardening, flushing the toilet, bathing and clothes washing. Harvested rainwater could reduce mains supplied water by up to 50 per cent and it: • Reduces metered water supply costs • Provides an emergency supply • Reduces demand on mains water • Reduces the rate of stormwater runoff and the demand on disposal systems
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• Provides an independent supply for watering the garden in times of drought
Raymond Kelly, Associate at TÜV SÜD, an international building services engineering consultancy, specialising in sustainable MEP (mechanical, electrical and public health), BIM (Building Information Modelling), lighting design, and vertical transportation.
Other efficient and environmentally friendly water supply solutions, such as low water volume flush toilets, the use of urinal cistern controls and low flow terminal fittings for tap outlets and showers, also deliver quantifiable water consumption savings. Unlike rainwater and grey water recycling, these solutions require little or no additional plant space and maintenance, making them easier to introduce into a typical system design. Leak detection systems can also be deployed, which alert building users, with automatic shut off facilities preventing major water wastage. BREEAM is one of the property industry’s recognised benchmark for the environmental rating of new and major refurbished buildings. In relation to water supply design it broadly aims to: • Reduce the consumption of potable water for sanitary use in new buildings by using water efficient components and recycling systems.
• Ensure water consumption can be monitored and managed to encourage reduction.
• Reduce the impact of water leaks that may otherwise go undetected.
• Encourage the specification of water efficient equipment.
8 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JULY 2020 Read the latest at:
www.bsee.co.uk
Health and wellbeing and the quality of the water supply must remain the key considerations when introducing efficient, environmentally friendly water supply measures. This necessitates a good match between the measure to be employed and the efficiency aspect targeted. However, too often complaints of poor water performance are the result of over-designed conservation measures which push a solution that isn’t compatible with the installation type. A good example of this is the specification of restricting devices to minimise water use which may not be suitable for appliances which require specific flow rates to operate effectively.
Under estimating design requirements at an early stage, as well as overdesigning and a lack of attention to detail can lead to all sorts of operational issues. For example, over-sizing the specification of cold-water storage tanks can lead to stagnation, whilst under-sizing could cause demand-supply problems.
Unfortunately, a ‘one fits all’ attitude to water services design is common in this highly automated age. Likewise, financial pressures can create barriers to the optimum design solution. For example, often cold-water storage plant space is shared with heat-producing plant, usually because there is pressure to reduce net floor area and increase cost savings by minimising plant space in a building. This can have a warming effect on the cold-water supply and potentially introduce the risk of bacterial propagation in the water supply. While adherence to water standards and regulations should ensure a level of compliant design, modern buildings and the drive for energy efficiency have created unintended consequences. As heat produced in a building no longer leaks out, this has introduced potential for heat gain to the cold-water distribution system.
The result is a risk of infection and proliferation of Legionella and similar bacterial infections. Likewise, the drive for fittings which minimise water consumption and the recycling of used water has created a need for new standards to specify pipe and plant sizing, as without it new systems could be over-designed.
It is estimated that only about 2.5 per cent of water on Earth is fresh and even less of that is safe to drink. While efficient water usage management is necessary to comply with national and international environmental conservation best practice aims, the direct benefit is a significant reduction in water consumption and cost.
About TÜV SÜD
TÜV SÜD’s Real Estate division is an international building services engineering consultancy. Its mechanical, electrical and sustainable design solutions help to ensure that buildings meet evolving legislation and technology requirements. Specialising in sustainable MEP (mechanical, electrical and public health), BIM (Building Information Modelling), lighting design, and vertical transportation, it delivers complex engineering projects across all sectors, from bases in the UK, Ireland and the Middle East. One of the few MEP consultancies in the UK to be BSI BIM Level 2 certified, TÜV SÜD’s Real Estate division is part of TÜV SÜD, one of the world’s leading technical service providers, which has more than 24,000 employees located across over 1,000 locations.
www.tuv-sud.co.uk/real-estate
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