Great innovations in sanitary engineering
Many of the important aspects of maintaining a system’s integrity by preventing sewer gases from entering living spaces, the water trap seal and system venting, had already been introduced and much work on improving the system’s response to the inevitable pressure fluctuations encountered in a fluid transport system were well under way.
This paper explores the work of early innovators in the field and tracks developments through the 20th Century to the present day and considers how this early work has often been sidelined in favour of less scientific design techniques in codes and standards. It is hoped that this paper will highlight the early work of those attempting to create a safe, hygienic environment for people, for the first time. This work should be remembered in a favorable light, not least because of their commitment in the face of opposition, but because their observations were based on the sound engineering and scientific methods often absent from deliberations in the industry today.
Building drainage system research and modelling is often concerned with physical phenomena on a minute scale. This author’s paper contribution to the CIBW62 symposium in Taiwan in 2006 considered the risk of trap seal depletion due to solids falling down a vertical stack, with the duration of the resulting air pressure transient measured in milliseconds. With the introduction of modern technologies such as the positive air pressure attenuator comes a need to measure performance over a very short timescale, again measured in milliseconds. In stark contrast to the flows found in public sewer networks, most flow scenarios in building drainage systems can be simulated in numerical models using total simulation times of less than one minute. Scale is an important issue in engineering science and building drainage systems are no exception. Shorter time scales and larger physical variables (such as pressure, velocity) are inevitable the closer to the point of system entry one looks.
The modelling of a building drainage system operation focuses mainly on the derivation of boundary equations for inclusion in numerical models, a process which forces the researcher to determine the relationships involved forensically and, in many cases, in an isolated manner. The combination of small time scales and the need for accurate system boundary information encourages researchers to look at a system on a ‘micro’ level.
This paper takes a step back from this approach and considers some of the ‘macro’ implications of building drainage system design, but from a historical perspective. It is hoped that this approach will highlight that some of the important issues facing the drainage research team today, have faced researchers since the birth of modern sanitary engineering, arguably considered to be in the 19th Century. The myths alluded to in the title of this paper are in effect the superstitions and mis-information which have dogged this area of engineering, much more than any other. The ‘legends’ refer to seminal work by early investigators, often forgotten, but which have proved their worth in modern times.
It should be noted that the issue of sanitation provision follows particular cultural and geographical standpoints, and while every effort has been made to make this paper as general as possible, it is inevitably written from a European/American/Western perspective. This is in part due to the influence that modern gravity fed drainage systems have had on world sanitation, but also in part due to the background of the author.
Sanitation, development and progress
Development is a much contested term. It describes a process of change in a society or community from one way of being to another. It is concerned with progress and is usually associated with industrialization and democratization though many others see the process as a vision. This contention has led to entrenched views on how a people should adapt to changing times and progress forward.
The process of development is inseparable from the concern with the disposal of human waste. It can be argued that a culture’s approach to disposal of human waste is a good development indicator. Much has been written on early drainage and sanitation systems. The early systems found in Turkey go back 8000 years and 4000 years in Greece. The system most of us are familiar with is the Roman system of water supply and sanitation which in many ways forms the foundation of our modern systems today. In many respects very little advancement occurred from the fall of the Roman Empire until the 15th Century with little remaining of those Roman systems.
Progress towards a modern, industrial, developed world can arguably be traced back to the beginnings of the industrial revolution, which started in Britain but spread quickly throughout Europe and the U.S. With industrialization came a rapid move from a predominantly rural, agrarian society to a predominantly urbanized, industrialized society and with this came all the problems associated with intensive living in cramped conditions with poor sanitation.
The industrial revolution; sanitation reform imperative
With the industrial revolution came a dramatic shift in living. The move from a predominantly agrarian, rural society to a more urban, industrial one brought many challenges. The least of these was how to deal with sanitation on a massive scale.
The 19th Century, often referred to as ‘Victorian times’ after the monarch who reigned from 1837 to 1901, saw many changes in Britain. These changes in approaches to living and work were exported to many parts of the world as part of the ‘imperial package’ where ‘development’ was ‘done’ to the colonized for their own benefit. With this export and the increasing influence of the super powers of the day a ‘standard’ was created in hygiene and sanitation with notably European origins.
It has been argued that the promotion of hygiene and sanitation followed the missionaries who inevitably followed the colonizers. That the theme of ‘Cleanliness is next to Godliness’ somehow pervaded the whole of Victorian thinking such that to bring the ‘word of God’ to a people involved bringing better hygiene and sanitation. This is the view of many commentators, notably Comaroff who considered this a further erosion of local (sometimes better) traditions in this area. There is an alternative view that the driver for sanitation reform in Victorian Britain was not so much a ‘faith’ based idea but an intense apostasy for reform in general.
Regardless of its origins, it is without doubt that the idea of public health reform as universally advantageous accords not only with our own sense of the desirability of sanitary techniques such as flush toilets and water-borne sewerage, which have become naturalized in the West, but also with a narrative of historical progress.
The consequences of an ‘evangelization of sanitation’ linked with colonialization has been a long standing connection between the colonized and the colonizer in terms of trade and progress. In terms of sanitation standards this has often meant the adoption of codes and standards which are not tailored for particular needs. For example in Hong Kong, where the use of sea water to flush WCs is wide spread, research and design codes should reflect this, but the drainage codes and design guides are based on U.K. standards which were derived using clean cold water. This anomaly is just one example of how the use of standards produced for a particular place and time can be totally irrelevant to another place at another time.
Embryonic codes for plumbing
To most people the building drainage system lurking beneath their pristine ceramic and stainless steel appliances presents a mystery beyond their usual ‘need to know’. How their sink full of soapy water gets from their newly refurbished kitchen island to the municipal treatment plant is of little or no interest, and likewise, few people ponder the similar journey from the WC, bath or bidet in the bathroom; until that is, they are suddenly faced with a foul smell from ‘somewhere down there’ or are met by a filling WC bowl which keeps on filling and pours onto the new floor covering. The mystery surrounding the drainage system suddenly deepens on the presentation of an unfeasibly costly repair bill.
The disposal of human waste is an issue the world over – cultural perspective and local taboos governing many of the practices surrounding its management. It has been conjectured that in many ways the approach taken to waste management is a very useful representative indicator of ‘level of development’ within a society. While a fuller discussion of this falls out of the remit of this paper it is useful to note that many of the great ‘civilizations’ in history are remembered for the attention paid to sanitation.
In truth there are few real mysteries about the operation of a building drainage system. The underlying principles governing the flows of all fluids (water and air) have been well described and indeed applied to the building drainage system for both design (making the system work) and forensic analysis (finding out why it didn’t work) for many years. It is worth remembering that while humans have many cultural taboos surrounding the bathroom, which have contributed to the myths surrounding the drainage system, there is a strong scientific basis for the movement of waste by means of water which has a long tradition, going back thousands of years. However the advances made in the past two centuries form the basis for our modern systems.
The age in which the innovation of safe and practical building drainage and plumbing were at the cutting edge of technology was in the late 19th Century. This work was initially carried out by scientists and notable engineers of the time.
In the U.K. the water trap seal was invented by Cummings as early as 1775. Cummings was an Eengineer and a watchmaker and resurrected the idea of a flushing WC originally invented by Harrington in the 17th Century. While much of the parts of the system had been around for some time it wasn’t until the mid 19th Century that any impetus existed to sort out the poor sanitary conditions in large towns and cities. In 1842 Edwin Chadwick, an English civil servant, published his ‘Report into the Sanitary Conditions of the Labouring Population of Great Britain. This report initiated a process of reform which prompted investment in sanitation as a public health priority in the slum conditions created by the rapid expansion of British cities as a result of the Industrial Revolution.
Such was the importance of sanitation at the time that even the eminent scientist/engineer, Osborne Reynolds, whose work on turbulent flow was seminal and still considered central to any discussion of fluid dynamics today, was moved to write a paper on ‘Sewer Gas and How to Keep it Out of the House’, which dealt with sanitation in the slums of Manchester, England in the late 19th Century.
While this work was continuing in Europe, in the United States, architects, scientists and engineers were facing their own growth problems as immigration from Europe and rapid economic expansion provided the driver for a building boom. Work (reported by) a notable Engineer, George Waring in his book ‘How to drain a house, practical information for householders’, highlights the depth of knowledge available at the time.
Waring was an influential sanitary engineer in his day, an innovator in public sewage works and an advocate of the link between poor sanitation and the spread of disease. He was consultant sanitary engineer to the President of the U.S.A. at the Whitehouse in Washington DC.
While some of Waring’s approaches are outdated, his writings did show that he had a firm grasp of the link between what was going on in the drain and its relation to fluid mechanics. The following extract illustrates this well:
“Efficiency [of the vent system] is due entirely to the admission of air fast enough to supply the demand for air to fill the vacuum caused by water flowing through some portion of the pipe beyond the trap, it is not only a question of having an opening large enough to admit air, but of having an adequate current led freely to the opening…a one inch pipe, for example may admit air fast enough, while a larger [longer] pipe of same diameter, or a smaller pipe of the same length would not do so” -Waring, 1895 pp 101-102
What Waring is suggesting here is the importance of pipe friction and the necessity to analyze the problem in a time-dependent and dynamic way. This is a crucial point and one which has driven much of the computer-based systems modeling carried out in the past 30 years. Building drains carry unsteady flows which means that they are rapidly changing and cannot be analyzed using simple calculations based on steady, unchanging flows, which are often used for the slower moving public sewer networks.
A contemporary of Waring, the Boston Architect J. Pickering Putnam went further in his 1911 book ‘Plumbing and household sanitation’ in which he doubts the necessity for any venting on properly designed systems with anti-siphon traps – he even suggests the use of mechanical air vents in close proximity to water traps in order to overcome siphonage problems.
Putnam’s conclusions followed years of experimentation on water trap seals and venting arrangements based on sound fluid mechanics principles. The point raised by Waring above was further promoted by Putnam following a series of experiments on pipe friction carried out by the Massachusetts Institute of Technology.
Putnam’s 718 page book concludes with a paper delivered to the 44th annual convention of the American Institute of Architects in San Francisco, Jan 18, 1911, entitled ‘Better Plumbing at half the Cost’ in which he suggests a single pipe system for multi-storey buildings based on an economic argument and the years of experimentation and experience of the author.
It is noteworthy to mention that of the reasons cited by Putnam for the failure to adopt such simplified systems the most significant was the conservatism of the plumbing associations, and the industry in general. This work on the single pipe system was further investigated in the U.K by the Building Research Station in the 20 years or so following World War II. Again, the driver was a rapid expansion in building projects as the war torn country was rebuilt. Work published by Wise in 1957 concluded that the single pipe system (known as the single stack system in the U.K.) was a robust, safe and economical option and that, if properly designed, building drainage systems do not require every trap to be vented.
So it seems that the issues surrounding the adoption of new approaches to venting are the same today as those experienced by investigators in the late 19th Century. Much of the cynicism surrounding new approaches and techniques was a result of the intervention of plumbers and those associated with the industry for whom a move to more efficient installations posed a threat.
Plumbers or sanitary engineers?
The distinction between the ‘plumber’ and the ‘sanitary engineer’ may seem an unnecessary one, however the plumber as tradesperson, artisan, wields a considerable amount of power in the industry compared with many other technicians in similar engineering disciplines. This influence is due in part to the trepidation with which most people view the whole process of removing unwanted waste from a building. The plumber is the front line for many and the one to advise on the efficiency or otherwise of particular installation options. The parodying of the plumbing profession is not new as this quote from an early American home economics text by a Mrs Plunkett shows:
“Next to the mother-in-law, the plumber is the best-abused character of the period; he is the perpetual butt of the “funny man” of the daily press, who represents him as gallivanting about Europe, while his impoverished customer wrings his hands in vain lamentations on the hither shore of an ocean he has no money left to cross.”
Mrs Plunkett goes on to defend the plumbing fraternity by suggesting that there are just as many honest plumbers as there are carpenters, masons or painters. The point she makes is that the consequences of a ‘poorly compacted joint’, as she puts it, is much more evident than the work of other trades. The point she makes is a very good one, and still relevant today. The consequences of poor plumbing are horrendous. The fear of these consequences has led to an innate conservatism among plumbers when it comes to adopting new techniques and technologies. They are perhaps right to be wary since it is their reputation that will suffer in the event of a catastrophe.
The evolution of the sanitary engineer on the other hand has been less well documented. The job of designing the drainage system is often left to a junior architect or an M&E engineer with little true knowledge of this specialist system. In stark contrast to the early innovators inspired by the need to provide safe sanitation in a changing world, the modern sanitary engineer has been encouraged to ignore the dynamism of system response in favour of a discharge/fixture unit approach which is based on probability of appliance usage and steady state design.
This combination of a fearful plumber and an ill-equipped sanitary engineer has made innovation difficult in modern drainage systems design. It has also limited the ability to apply systems modelling to the wider challenges facing the discipline today.
By examining the successes and failures in developments towards modern drainage system design and implementation, it may be possible to chart a course through some of the challenges facing the discipline in the near future. The challenges facing us into the 21st Century include:
•The improvement of services for the vast number of people without safe sanitation in the world today,
•Providing an adequate response to the threat of an unpredictable, chaotic climate system
•The production of codes and standards flexible enough to cope with this changing environment.
It can be argued that the most pressing of these challenges is the provision of safe sanitation to the 1.2 billion people still with inadequate provision.
The situation is improving, but only slightly, and that the poorest areas in the world still have the lowest access to both improved water supply and improved sanitation.
The impact of a globalizing economic system cannot be ignored in all of this. The increase in urban poor and the creation of slums in many big cities have produced conditions similar to those addressed by Sir Edwin Chadwick and Reynolds in Britain in the 19th Century. The imperative to apply modern engineering and organisational understanding to solving these problems has never been greater.
Much of the modern day understanding of sanitation systems engineering has been in place for a long time. The work carried out by pioneering researchers focussed heavily on the fluid dynamics of the system. This led to the conclusion that building drainage system networks could be simplified, however, resistance from others in the industry thwarted moves to have these systems adopted much earlier than they inevitably were. The strength of debate between the innovators and the conservatives led to entrenched views early on which have proved difficult to overcome since.
The expansion of European empires in the 19th Century led to the adoption of, in many cases, inappropriate technologies and techniques in places where water is acutely short. It was not only inappropriate technologies which were exported but codes and standards as well, many of which are still adopted today.
The challenges facing the discipline in the near future are not less onerous than those facing engineers and planners in the 19th Century when many European and American cities were expanding at a fast pace. Early innovators combined sound engineering fluid mechanics with a sense that they could make a real difference in the world. Our challenge is to apply modern techniques and technologies to the considerable problems still facing the world of building drainage and sanitation today.