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Approximately 150 litres of treated water is consumed per person every day, amounting to approximately 50m3 of water per annum per person.

 

An efficient water supply system along with recycling systems can save the tenants and landlords  more than 50% on the water bill.

 

The choice of fittings or water recycling system will depend on location, present water cost, the existing water supply strategy and the type to tenants.

 

Refurbishment of tower blocks presents an opportunity to:

  • modernise fittings and supply system

  • reduce water consumption and cost

  • future-proofing against possible scarcity of supply

 

REFURBISHMENT OPTIONS

 Basic

Install a booster pump

Install water efficient WCs

Install low flow showers & taps

Good

Harvest rain water

 Exemplary

Provide a drain-water heat recovery

Recycle grey water

Water consumption per person per year

Install a booster pump

 

Water supply companies in an effort to reduces water loses through leaks are looking to reduce the mains water pressure. The pressure reduction will affect high-rise dwellings most. Some flats, especially those on higher floors, face the prospect of having no water supply.

 

The minimum standard for the water pressure from the water utilities is 1 bar [10m head of pressure], at the external stop tap, at a flow of nine litres per minute. This should be sufficient to fill a one-gallon container in 30 seconds. This level of pressure does not override the duty to supply water constantly at a pressure to reach the upper floors of properties1.

 

To mitigate this problem, prior to refurbishment water pressure should be checked and the water supply companies should be contacted to investigate their future plans.

 

Installing pumps to boost the pressure and making relevant changes to the plumbing in some high-rise blocks may required.

 

Other considerations

 

Controls

The energy used by booster  pumps can be high. Controls should be installed to match the pump operations with actual water demand  in the building. The controls alter the speed of the pump based on the water demand at any given time by way of pressure transducers installed on plumbing risers at the top floor of a tower block. The transducer is electronically connected to the control panel in the plant room.

 

Water meters

Individual water meters may be considered whilst rejuvenating the plumbing system, as metering will help transfer greater responsibility to individual tenants. Ensure that the meter is pulse output capable such that it can be electronically read if required for remote monitoring or for connection to a building management system.

 

Benefits

  • Good water pressure in kitchen and toilets

  • Improved quality of life for the residents

Typical Cost
□  n/a
schematic diagram

Funding opportunities:
□  Some water supply companies cover the cost of installing pumps.

Also see:

□  n/a

More information:

□  London  Housing magazine: Pressure grows as pressures drop

Suppliers:

□  1Ofwat

To register as a supplier click here...

 

Install water efficient WCs

 

WCs are typically responsible for the largest use of water in dwellings [around 30%] . In tower blocks built in the 60's and 70's, the  WCs were fitted with flush volumes  between 13-9 litres1.

 

The current regulation require 6 litres maximum as flush volume for all new WC suites. Therefore, changing the WC cisterns can potentially reduce water consumption.

 

Dual flushing cisterns for WCs offer the best solution.

  • Duel flush cisterns: these come with a half flush [3 litres] and a full flush [6 litres] option.

  • Ultra-low flush: Alternatively, WCs with ultra-low flush volume of 4.5 litres can be installed.

Other considerations

 

Elderly

Consider high rise pan for tower blocks housing a high propotion of elderly people.

 

Disabled

Additional features such as a 'hinged support arm' and grab rails may also need to be installed in some flats. Also consider redesign of the toilet layout to accommodate Part M requirements.

 

Inefficiencies

Most WCs in reality consume about 10-25% more than the specified flush volume they were designed to use. This is mainly because water enters the flush tank during flushing.

 

Benefits

  • Reduce water consumption
  • Upgrade appearance
Water consumption through WC per flat /year
Typical Cost

□  330-400/WC

Assuming IDO WC with concealed cistern from Construction Resources; Flush volume: 2.5/4 litres

Funding opportunities:
□  The ECA Scheme

Also see:

□  Low flow showers & taps

More information:

□  1Elemental Solutions

Suppliers:

□  www.greenbuildingstore.co.uk

□  www.constructionresources.com

To register as a supplier click here...

 

Install low flow showers & taps

 

Use of taps, bath and showers significantly increase the energy and water consumption in dwellings. Therefore, limiting the rate of flow of water through these fittings can help reduce water consumption.

 

Standard toilet specifications in tower block flats have 10 litre per minute taps and  180 litre capacity baths with rinse shower.

 

The following changes may be carried out whilst refurbishing toilets and kitchens.

  • Installing low-flow aerated taps to wash basins  with flow rate less that 5 litres per minute

  • If the toilets have showers, changing the shower head to one with maximum flow rate less than 6 litres per minute

  • If the bath tubs need replacing, choose the one with less than 150 litres capacity.

 

Other considerations

 

Water pressure

Ensure that the building has adequate water pressure prior to replacement of sanitary fittings

 

Elderly and disabled

Shower Chairs, Bath Benches and Shower Seats may be required in flats with elderly or disabled residents

 

Washer-less taps

Replacing  taps with washer-less values can help reduce maintenance cost as these fitting tend to have low breakdown rate.

 

Benefits

  • Up to 50% water consumption from taps can be saved
  • Upgrade appearance
  • Reduce energy for DHW
  • Lower maintenance cost
Low flow taps: water consumption/ flat /year
Typical Cost

□  Shower flow restrictor, 10 litre for fittings to shower hose: 15/fitting

□  Monoloc tap, single lever with pop-up waste, incl. 6 litre aerator or 1.7 litre spray fitting: 83/fitting

 

Funding opportunities:
□  The ECA Scheme

Also see:

□  water efficient WCs

More information:

□  1Elemental Solutions

Suppliers:

□  www.greenbuildingstore.co.uk

□  www.heatandplumb.com

To register as a supplier click here...

 

Harvest rain water

 

Rain water falling on the rooftops and the surrounding areas can be collected and stored in catchment tanks. This water can then be used for non-potable uses i.e., flushing toilets, cooling towers, steam boilers, car wash and garden irrigation. Thus saving on precious purified potable water from the mains.

 

Estimating Annual rainwater collection

 

Annual water collected [m3] =

Roof area [m2] x rainfall [m/year] x losses [0.6 to 0.8]

 

Collection potential for tower blocks

Although harvesting rainwater from tower blocks is technically feasible, it tends to provide lower cost-benefits when compared to a low rise building due to its smaller roof to total floor areas ratio.

 

For example, a typical tower block in London,  will only be able to provide approximately 5-10% of its annual demand for WC flushing using rainwater harvesting.

 

 

Other considerations

 

Ecological pond

The harvested rain water can also be used to feed an ecological pond on site. This could help improve the local ecology and biodiversity.

 

Bore hole

A bore hole for water supply could also be consider in suitable areas. This source of natural untreated water, could be especially beneficial in areas with a rising water table or with uncertainty of water supply with adequate pressure.

 

Benefits

  • Lower fresh water use [<10%]
  • Reduce storm water runoff
  • Less energy and chemical use
  • Groundwater recharge
schematic diagram
Typical Cost

□ n/a

Funding opportunities:
□  The ECA Scheme

Also see:

□  Recycle grey water

More information:

□  www.rainwaterharvesting.org

□  www.green-rated.org

Suppliers:

□  www.rwc.co.uk

To register as a supplier click here...

 

Provide a drain-water heat recovery

 

A large amount of energy in residential buildings is used for heating water for baths, showers and washing machines. Most of the heated water after its initial use is wasted down the drain.

 

The heat from the waste hot water can be captured and reused with the help of heat exchangers. The recovered heat can then be used as preheat for the existing heating system. The system converts the grey water drainpipe into an energy-efficient heat exchanger, which feeds back the recovered heat  to cut the cost and increase the  capacity of residential water heaters: both gas and electric.

 

There are different types of heat exchangers available in the market depending on the orientation of the pipeline [vertical or horizontal], storage space and size of the system.

 

Both the EU and US are actively promoting its commercial development.

 

Benefits

  • Conserve energy
  • Reduce heating cost
  • the DHW system can be undersized
Typical Cost

□  Drain water heat recovery unit: 60/flat

Funding opportunities:
□  The ECA Scheme

Also see:

□  n/a

More information:

□  CADDET Newsletter 1997: GFX

□  DOE

□  EC research: Warmit

Suppliers:

□  AK Industires Ltd

□  GFX Technology

To register as a supplier click here...

 

Recycle grey water

 

Grey water is the waste water that comes out of the sinks, bath tubs and washing machines excluding WC and water with food wastes.

 

A grey water recycling system  collects, treats, stores and re-distributes the grey water for appropriate uses within the flat or the community. The typical use for treated grey water includes, WC flushing and garden irrigation. There are three basic ways to treat grey water i.e., physical, chemical and biological. The appropriate treatment will depend on the space available, budget, acceptance of the residents and quantity of grey water.

 

Potential for tower blocks

In tower blocks, the grey water can be used for WC flushing. In most flats the WC flushing demand tends to be well balanced with the grey water availability from baths, hand wash and washing machines.

 

The collection, treatment and storage can either be centralised or done in each flat or group of flats [floor by floor]

 

If space is available on each floor, one possible option,  can be to use rainwater for the WC's in the top most flats and a  floor by floor system to treat grey water from the flats above for the WC in the flats below. This process will help recycle most of the grey water and reduce total water use by 30% [see schematic diagram].

 

 

Other considerations

 

Water metering

Water meters to individual flat must be considered prior to installing a grey water system.

 

Reed bed sewage treatment

Biological treatment of waste water i.e., grey and black could be consider if adequate space is available on site

 

User involvement

A grey water system will require maintenance from time to time and there is also a risk of odour and colour related issues. Therefore, it is crucial that the residents must be involved in the implementation of the system. A pilot test or/and consultation with residents in building where this system has been previously used is advisable.

 

Benefits

  • Lower fresh water use [upto30%]
  • Less strain on septic tank or treatment plant
  • Reclamation of otherwise wasted nutrients
Schematic diagram
Typical Cost

□  grey water system: 900/flat

Funding opportunities:
□  The ECA Scheme

Also see:

□  Harvest rain water

More information:

□  n/a

Suppliers:

□  n/a

To register as a supplier click here...

Project partners:           | Price Myers: Sustainability |Battle McCarthy | Architype | STBI | Franklin Andrews |            

           

Copyright 2004  Price & Myers Sustainability                                 last updated: 11/25/11

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