Dry Drains presentation, CIBW62 Dusseldorf, 2009 Dry Drains: Myth, Reality or impediment to water conservation. Professor J.A. Swaffield Emeritus Profesor School of the Built Environment, Heriot Watt University, Edinburgh, Scotland. 1 j.a.swaffield@hw.ac.uk School of the Built Environment
Dry Drains The concept that ‘dry drains’ could be a consequence of water conservation was initiated in the US where ‘concerned groups’ argue that further reductions in w.c. flush volume will reduce the drain flow so solid transport – or ‘drainline carry’ - becomes impossible. In January 2009 IAPMO signed an MOU with - the Alliance for Water Efficiency (AWE), the Plumbing Heating and Cooling Contractors National Association (PHCC), the Plumbing Manufacturers Institute (PMI) and the International Code Council (ICC). The five associations agreed to call this coalition the Plumbing Efficiency Research Coalition (PERC). Information provided by Pete DeMarco, IAPMO, e-mail to Goncalves, cc Swaffield 2 School of the Built Environment
Dry Drains presentation, CIBW62 Dusseldorf, 2009 PERC’s first joint project will be Drainline Transport PERC is developing a Request for Proposals to be sent to - * universities for the CFD work, * qualified test labs for the laboratory work, * plumbing contractors for the field study work , so that funding can be sought from the US government and other entities to underwrite the research’. PERC (Pete DeMarco, IAPMO) states that ‘of course, we also intend to conduct an international literature search. We have not conducted our searches yet, pending funding’. 3 School of the Built Environment
Frankfurt ‘Dry Drains Forum’ March 2009 In March 2009 a Dry Drains Forum was hosted at the ISH exhibition by Jeff Patchell’s organisation and several speakers presented arguments for and against the concept. The US contribution harked back to the 1992 Energy Bill that introduced 6 litre w.c. flush volume without consultation and was concerned that any move towards 4 litres would be achieved in a similar fashion. The UK and Australian contributions emphasised the role of climate change and our ability to design for reduced flush volume – quite different approaches. 4 School of the Built Environment
Dry Drains? It is necessary to rationally examine the concept of the ‘dry drain’. The following areas need to be considered – 1. What effect will climate change have on drain throughflows? 2. What effect will demographic and social changes have on throughflow? 3. What can we learn from previous research? 4. What design or installation strategies might be used to offset any perceived problem? 5 School of the Built Environment
Water conservation remains a major UK issue ‘..climate change is the biggest challenge facing the world today.. this landmark scientific evidence shows that we need to tackle the causes of climate change and deal with its consequences.’ Hilary Benn Environment Secretary June 18th 2009 on the release climate change scenarios for the UK from 2050 to 2080. 2001 Issue already identified in the UK 2007 6 School of the Built Environment
UK mean annual rainfall, 1971 - 2000. At least a Possible changes fourfold WET by 2050 – variation West of Scotland from North winter rainfall to West to rise by 15 to South East is 29% apparent from this SE England historic data summer rainfall across the to decrease by 19 DRY Source – Met. Office 2006. UK to 41 % 7 School of the Built Environment
Domestic water usage and drain throughflow rises due to demographic shifts. Demographics and user preferences have changed, and will change further, the water use pattern in the UK. By 2030 ----- * England will have 27.8 million households - 6.3 million (29%) more than 2006, an INCREASE of 252,000 per year. * One person households are projected to increase by 163,000 per year, OR two-thirds of the overall increase in households. * 32% of households will be headed by those 65 or over, up 26% on 2006. * 18% of the total population will live alone, up from 13% in 2006. THESE CHANGES WILL AFFECT WATER DEMAND……. A single person uses – 2 times as much as a person in a group of 4 and 4 times as much as a person in a group of 8. 8 School of the Built Environment
Water usage and drain throughflow have risen over the past decades… 1976 2001 2009 115 litres per 143 litres per UK Govt. figures capita per day, capita per day, suggest 150 litres Population 55m Population 60m per capita per day, Note UK Govt. Building Regulations now propose a target of 125 litres per capita per day i.e. > 1976. While water conservation will reduce individual usage, demograhics will increase the overall total. Water conservation remains essential, holding water usage at current levels will be the challenge. 9 School of the Built Environment
Comparisons of UK appliance use data 2000-06 identifies water conservation targets… The w.c. REMAINS the major component of domestic and commercial building water usage. Major reductions have been made in the past 20 years. % water use data, 2000 WRc water usage data 2006. Washing m/c 20% Toilet 31% W.c. Dishwasher 1% 31% Bath W.c. 15% Kitchen Sink 34% 15% Basin Data taken from 'Water efficiency 9% Outdoor use in the home', Parliamentary Office 4% Shower of Science and Technology, Note 5% 135, 2000. 10 School of the Built Environment
Coping strategies….. What can we learn from previous research? • W.c. design is central, • Identify and understand the parameters defining solid transport and develop predictive models, • Introduce careful drainage system design to minimise probability of deposition, • Understand and apply 30 + years of research freely available through international published papers. 11 School of the Built Environment
W.C design over past 100 years hhas demonstrated the potential for water conservation. 45 UK US Reduction in w.c. flush volume 40 Scotland from 1900 to 2007 - illustrating US the potential for water saving UK 35 based on appliance design rather Sweden Rural Appliance flush volume, litres. UK Experimental than user opinion. UK Experimental 30 EU UK 25 US Microphor Australian proposals UK ODA for the use of non Sweden Urban 20 circular section US Aus 6/3 Dual Flush building drains may UK 6/4 Dual Flush 15 allow further UK pneumatic -80 -60 -40 -20 0 20 40 60 80 reductions in flush Aus 4/2 Dual Flush volume without 10 Poly. (All appliances) reduction in transport efficiency. 5 Date 0 1880 1900 1920 1940 1960 1980 2000 2020 12 School of the Built Environment
ODA / Twyfords / Brunel 3 litre w.c. 1984 Low flush volume w.c. design is now the norm, eg Caroma and many other manufacturers. The understanding has been there for 25 years as shown by this 1983 Brunel University w.c. used in Botswana, Lesotho, China and Brazil but NOT the UK. Examples of this w.c. still exist at HWU 13 School of the Built Environment
Solid transport at reduced flush volumes Reducing w.c. flush volume is a first line response to water conservation targets. Research has shown that this may be achieved WITHOUT exacerbating other drainage problems Extensive laboratory and site testing over 30 years allows the identification of the parameters defining solid transport and the development of predictive models that can be of direct value to the system and appliance designer. 14 School of the Built Environment
Solid transport dependence on w.c. and solid parameters based on both laboratory and site testing. Based on extensive solid transport testing the Transport distance dependency on selected variable groups referred to a datum condition. distance to deposition 1 DECREASES as - sg, datum value 0.2 solid mass increases, 0.9 F/FB, datum value 9 litre wet/dry wc. Fwc/F, datum value 9 litre 0.8 flush volume behind solid wc. wt/d^2, datum value 5% decreases, 0.7 F/FB C3 / C3(datum) specific gravity of solid 0.6 increases, 0.5 cross sectional area of sg 0.4 wt/d^2 solid increases, 0.3 Fwc/F overall flush volume decreases, 0.2 0 1 2 3 4 5 6 7 8 9 10 / π ( datum value) π (in turn sg, F/FB, Fwc/F, wt/d^2, wet/dry) drain slope decreases, and drain diameter NO UNKNOWNS LEFT HERE. increases. 15 School of the Built Environment
Site testing of male and female restroom discharges, Greenwich Hospital, confirmed the identified mechanisms. 1.2 SITE TESTING CONFIRMED UNDERSTANDING 25 YEARS AGO 0.8 Solid velocity, m/s. Vsolid, Run 581, Tissue, 200mm long, thick, flat. Vsolid, Run 641, Tissue, 425mm long, medium, flat Vsolid, Run 833, Tissue, 200mm long, thick, irregular. Vsolid, Run 846, Tissue, 200mm long, medium, irregular. 0.4 Vsolid 1, Run 422 25mm long, 25mm dia stool, submerged. Vsolid 2, Run 422, 50mm long, 25mm dia. stool, submerged. Vsolid 3, Run 422, 150mm long, 37mm dia stool, submerged. Vsolid 4, Run 422, Tissue, 150mm long, v ery thick, flat. 0 15 20 25 30 35 40 45 50 Drain length and gradient combined as (L/G)^0.5 16 School of the Built Environment
W.c. flush parameters are CENTRAL to solid transport efficiency. THE RELATIVE IMPORTSANCE OF W.C. DESIGN PARAMETERS ARE UNDERSTOOD F wc - design w.c. flush volume Solid discharged W.c. discharge, litre/second from w.c. F - reduced flush volume F B - Flush volume discharged behind solid Probably the most important Time, seconds w.c. design parameter.. W.c. Discharge Profile. 17 School of the Built Environment
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