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On intercepting traps and watertight drains
~66
ON I N T E R C E P T I N G
TRAPS AND WATER-TIGHT
ON I N T E R C E P T I N G T R A P S A N D W A T E R T I G H T DP,.AINS. ~" By T. 1~)~ COURCY MEADI~, M.Inst.C.E,, :Engineer and Surveyor to the Hornsey Local Board.
Iniercepting l"raps.--It is thought by some that there is" no difference between the gases generated in sewers and those to be found in properly constructed and disconnected drains, and I am free to admit that I accepted this erroneous view as correct, until certain difficulties in connection with sewer and drain ventilation it~duced me to give special attention to the subject. Without entering into particulars of the experiments which I made when investigating the matter, I would like to point out that when a drain is properly constructed and properly worked, all sewage entering it passes away to the sewer within the space of a few minutes, and, consequently, there is no time for it to decompose in the drain. Any gases given off from matter adhering to the interior of the drain are constantly diluted by the current of air passing through it, and are discharged into the atmosphere, above the level of the house, in an inoffensive state, I n a system of sewers there is, however, quite a different state of things ; each local sewer receives in eight hours the bulk of the sewage which passes tl~rough it every 24 hours, and during the remaining 16 hours the flow is, as a rule, very small indeed--frequently but a mere d r i b b l e - - a n d quite insufficient to render the sewer self cleansing for the time being. During this period sewer gases are largely generated, and where intercepting traps are not used, much of this foul sewer air is forced into the drains when the sewage rises in the sewers. I find that even under favourable conditions the velocity of the air in sewers is much iess than usually found in properly made drains; consequently the air of sewers, although more impure, is diluted by fresh air to a much smaller extent, and, therefore, should be removed, as far as practicable, from the dwelling. Looking at this question from a purely official point of v~ew, one might perhaps be tempted to favour the discontinuance of intercepting traps for the p u r p o s e of assisting the ventilation of the public sewers ; but, from experience gained after years of careful investigation of sewer ventilation and drainage, I feel that I cannot advise a course which I consider lraught with danger to the inhabitants, more especially to these who occupy small class property, where the fittings are generally of a cheap and unreliable description. In districts of a semi-rural character, where there is plenty o f open space surrounding each dwelling, and where all drains are kept outside the external walIs, the danger of converting house drains into sewer ventilators may be lessened if special care is taken *From a special report to the Hornse¥ Local Board. See also remarks in last month's PUBLICHEALTIt (p. 234 ).
DRAINS.
in fixing the ventilating pipe and maintaining it in an air-tight condition. The drains of a considerable number of old houses in the district have been examined by your inspectors, and reported upon during the past twelve months, and several cases have come under my observation ~vhere, on the application of the smoke test to the drains of one house, in, a street where there were no intercepting traps , the smoke passed into the sewer, and from thence into the drains of neighbouring houses, and, through faulty joints or fittings, into the living rooms. In each of these cases the occupiers were persons of the working class, to whom loss of health usually means loss of livelihood. Drain Testi~.--W~th ordinary care there is no reason why all drains should not be laid in such a manner as to be perfectly water.tight, not only at the time they are laid, but also after they have been covered in and the building completed. Drains properly constructed will remain in a perfectly water-tight condition. I have had opportunities of testing the drains of houses which had been laid many years previously, and I found them perfectly water-tight. It is of little use to test sections of a drain before it is covered in, and to omit the final test of the finished drain on the completion of the building. T h e weak points are generally found in the branch drains, which, in practice, cannot easily be completed until the building is well advanced; and it frequently happens that carelessness in filling and ramming the trench over the drain is a cause of subsequent failure. Drainage work used formerly to be sub-let to a labourer, and this custom still prevails in some cases, although it cannot be expected that drains laid by piece-work should continue water-tight. Many persons think that the concrete which surrounds the drain beneath a building is suffÉcient to make it wa'er-tight, even assuming that there are leaking joints. This, however, is a mistake, the object of the concrete being to afford a rigid foundation and bed for the pipe, and for its protection generally, and not for the purpose of making it water-tight. I have seen leaky drains taken out of old buildings where conzrete had been used, and it was only necessary to observe the filthy condition of the concrete and the ground adjoining to have forcibly impressed upon the mind the necessity of laying all drains with perfectly water-tight joints. T h e subsoil of the greater part of the district of Hornsey is clay, and this, contrary to what is sometimes thought, is one of the most treacherous materials with wbich a drain trench can be filled. It is difficult to thoroughly consolidate the clay without risk of damaging the drain, and, even where the greatest care is used, cracks will almost invariably appear in the clay filling, as it becomes dry and shrinks, where protected from moisture by
HOUSING OF THE WORKING CLASSES IN RURAL DISTRICTS. the dwelling-house. These cracks afford a free escape for the gases from a defective drain into the building, and even the concrete with which the surface of the building is covered is not proof against their egress. T h e smoke test, although convenient fog testing traps and fittings above ground, is of no value in testing underground pipes. A drain may b e l e a k ing at every point, and yet appear perfectly sound on the application of the smoke test. There are many inventions for making the joints of stoneware pipes water-tight, but as s o m e of them are at present monopolies, I refrain from a!luding to them. I will, therefore, merely mention the " S t a n f o r d " form of joint which any builder can easity make on the ground or can obtain ready made from the manufacturers. T h e composition used in Stanford's joint is composed of one part of boiled tar, one part of clean sharp sand, arid one part and a half of s u l p h u r . T h e sulphur may be increased to one part and threequarters if it is desired to make the joints harder for the purpose of carriage, etc. Some builders in the districts are now using iron pipes i0 lieu of stone'rare. These pipes have the advantage of fewer joints, but should be well coated with Dr. Angus Smith's or other solution to prevent oxidation by contact with the sewage, and the joints should be run with lead. T h e information which I have obtained from the borough engineers and surveyors of many of the principal health resorts, and from the surveyors of some of the London vestries and the surrounding districts outside the metropolis shows that there is, with one or two exceptions, a very general consensus of opinion in favour of the use of intercepting traps, and of the necessity for water-tk_ht drains. CARRIAGE
OF
DIPHTHERIA
INFECTION
BY
CLOTHING ? - - I n the following case the infection of diphtheria appears to have been conveyed by clothing. On May 9th a child who had been visiting at Stratford was sent home to Writtle on account of a child in the house being attacked with croup. On the I6th the child who had returned home was attacked with diphtheritic croup and died on the 22nd, and the house was afterwards repapered, limewashed, and disinfected with sulphur. On the 2oth its brother was sent to Roxwell to his grandparents, and he remained there enjoying good health until July rst, when he was attacked with diphtheria. On June 25th it appears some clothes which had been in the room in which the younger child died were sent to Roxwell and worn by the patient, and this seemed the only possible way in which the child could have becom6 infected.*--From D r . ~hresh's 4 n n u a l Re#ort to the Chelmsford .R.S._/I. * For particulars of a case of diphtheria arising from infected rags after nine years, ~ee PUBLIC HEALTH, VoI. V.t p. 271.
267
THE PROBLEM OF HOUSING OF THE WORKING CLASSES IN R U R A L D I S T R I C T S . ~" ]~y GEORGE TURNER, M.B , D.P.H. Camb., M.O.H. Hefts Combined Districts.
IT appears a simple matter to condemn a house as unfit for human habitation and cause it to be closed. But it must be remembered that there are a certain number of persons in the district who must be housed, and must be housed too within a reasonable distance of their work, and that a cottage pulled down or closed is not necessarily rebuilt or repaired and made fit for habitation~ because the rent which an agricultural labourer can afford to pay does not make the erection of houses, such as would in these days be considered fit to live in, remunerative as a speculation. Cottages in the Hertford rural sanitary district, broadly speaking, are owned by two classes of people, viz., landowners who have built cottages for the convenience of their tenant farmers, and small owners who have invested their savings in cottage property as a source of income or perhaps as a provision for old age. Generally liltle trouble is experienced in dealing with the first class. Most ot the new cottages on the large estates are fit for anyone to live in, and, I should say, can yield little or no direct profit. Even when complaints are made with regard to the older cottages the complaints are usually attended to.
With the second class matters are far different ; the owners naturally expect to make money out of the buildings, which when originally bought were probably already far gone in ruin and on which little is spent in repairs. During the past twelve months I have m a d e house to house inspections of the district. The defects most usually discovered and reported were: General dilapidation due to ager rendering the cottage damp and unhealthy ; privies placed either against the house or too near to it ; newly-erected houses badly built ; bad or deficient supply of water. Sometimes the defects were such as to render the house unfit for human habitation without the possibility of any improvement short of demolition and reconstruction ; in other instances the cottages could be made habitable at a comparatively small cost, and the cases have been dealt with accordingly. I n the W a t t o n division of the Hertford Rural Sanitary District 22 houses were declared unfit for human habitation. Notices have in all cases been served on the owners, and the inspector's report states that : 4 houses were closed, 4 repaired, 2 partly repaired, 4 in hand, 5 the owners were waiting to make * From a special report to the Hertford R.S.A.
ON I N T E R C E P T I N G
TRAPS AND WATER-TIGHT
ON I N T E R C E P T I N G T R A P S A N D W A T E R T I G H T DP,.AINS. ~" By T. 1~)~ COURCY MEADI~, M.Inst.C.E,, :Engineer and Surveyor to the Hornsey Local Board.
Iniercepting l"raps.--It is thought by some that there is" no difference between the gases generated in sewers and those to be found in properly constructed and disconnected drains, and I am free to admit that I accepted this erroneous view as correct, until certain difficulties in connection with sewer and drain ventilation it~duced me to give special attention to the subject. Without entering into particulars of the experiments which I made when investigating the matter, I would like to point out that when a drain is properly constructed and properly worked, all sewage entering it passes away to the sewer within the space of a few minutes, and, consequently, there is no time for it to decompose in the drain. Any gases given off from matter adhering to the interior of the drain are constantly diluted by the current of air passing through it, and are discharged into the atmosphere, above the level of the house, in an inoffensive state, I n a system of sewers there is, however, quite a different state of things ; each local sewer receives in eight hours the bulk of the sewage which passes tl~rough it every 24 hours, and during the remaining 16 hours the flow is, as a rule, very small indeed--frequently but a mere d r i b b l e - - a n d quite insufficient to render the sewer self cleansing for the time being. During this period sewer gases are largely generated, and where intercepting traps are not used, much of this foul sewer air is forced into the drains when the sewage rises in the sewers. I find that even under favourable conditions the velocity of the air in sewers is much iess than usually found in properly made drains; consequently the air of sewers, although more impure, is diluted by fresh air to a much smaller extent, and, therefore, should be removed, as far as practicable, from the dwelling. Looking at this question from a purely official point of v~ew, one might perhaps be tempted to favour the discontinuance of intercepting traps for the p u r p o s e of assisting the ventilation of the public sewers ; but, from experience gained after years of careful investigation of sewer ventilation and drainage, I feel that I cannot advise a course which I consider lraught with danger to the inhabitants, more especially to these who occupy small class property, where the fittings are generally of a cheap and unreliable description. In districts of a semi-rural character, where there is plenty o f open space surrounding each dwelling, and where all drains are kept outside the external walIs, the danger of converting house drains into sewer ventilators may be lessened if special care is taken *From a special report to the Hornse¥ Local Board. See also remarks in last month's PUBLICHEALTIt (p. 234 ).
DRAINS.
in fixing the ventilating pipe and maintaining it in an air-tight condition. The drains of a considerable number of old houses in the district have been examined by your inspectors, and reported upon during the past twelve months, and several cases have come under my observation ~vhere, on the application of the smoke test to the drains of one house, in, a street where there were no intercepting traps , the smoke passed into the sewer, and from thence into the drains of neighbouring houses, and, through faulty joints or fittings, into the living rooms. In each of these cases the occupiers were persons of the working class, to whom loss of health usually means loss of livelihood. Drain Testi~.--W~th ordinary care there is no reason why all drains should not be laid in such a manner as to be perfectly water.tight, not only at the time they are laid, but also after they have been covered in and the building completed. Drains properly constructed will remain in a perfectly water-tight condition. I have had opportunities of testing the drains of houses which had been laid many years previously, and I found them perfectly water-tight. It is of little use to test sections of a drain before it is covered in, and to omit the final test of the finished drain on the completion of the building. T h e weak points are generally found in the branch drains, which, in practice, cannot easily be completed until the building is well advanced; and it frequently happens that carelessness in filling and ramming the trench over the drain is a cause of subsequent failure. Drainage work used formerly to be sub-let to a labourer, and this custom still prevails in some cases, although it cannot be expected that drains laid by piece-work should continue water-tight. Many persons think that the concrete which surrounds the drain beneath a building is suffÉcient to make it wa'er-tight, even assuming that there are leaking joints. This, however, is a mistake, the object of the concrete being to afford a rigid foundation and bed for the pipe, and for its protection generally, and not for the purpose of making it water-tight. I have seen leaky drains taken out of old buildings where conzrete had been used, and it was only necessary to observe the filthy condition of the concrete and the ground adjoining to have forcibly impressed upon the mind the necessity of laying all drains with perfectly water-tight joints. T h e subsoil of the greater part of the district of Hornsey is clay, and this, contrary to what is sometimes thought, is one of the most treacherous materials with wbich a drain trench can be filled. It is difficult to thoroughly consolidate the clay without risk of damaging the drain, and, even where the greatest care is used, cracks will almost invariably appear in the clay filling, as it becomes dry and shrinks, where protected from moisture by
HOUSING OF THE WORKING CLASSES IN RURAL DISTRICTS. the dwelling-house. These cracks afford a free escape for the gases from a defective drain into the building, and even the concrete with which the surface of the building is covered is not proof against their egress. T h e smoke test, although convenient fog testing traps and fittings above ground, is of no value in testing underground pipes. A drain may b e l e a k ing at every point, and yet appear perfectly sound on the application of the smoke test. There are many inventions for making the joints of stoneware pipes water-tight, but as s o m e of them are at present monopolies, I refrain from a!luding to them. I will, therefore, merely mention the " S t a n f o r d " form of joint which any builder can easity make on the ground or can obtain ready made from the manufacturers. T h e composition used in Stanford's joint is composed of one part of boiled tar, one part of clean sharp sand, arid one part and a half of s u l p h u r . T h e sulphur may be increased to one part and threequarters if it is desired to make the joints harder for the purpose of carriage, etc. Some builders in the districts are now using iron pipes i0 lieu of stone'rare. These pipes have the advantage of fewer joints, but should be well coated with Dr. Angus Smith's or other solution to prevent oxidation by contact with the sewage, and the joints should be run with lead. T h e information which I have obtained from the borough engineers and surveyors of many of the principal health resorts, and from the surveyors of some of the London vestries and the surrounding districts outside the metropolis shows that there is, with one or two exceptions, a very general consensus of opinion in favour of the use of intercepting traps, and of the necessity for water-tk_ht drains. CARRIAGE
OF
DIPHTHERIA
INFECTION
BY
CLOTHING ? - - I n the following case the infection of diphtheria appears to have been conveyed by clothing. On May 9th a child who had been visiting at Stratford was sent home to Writtle on account of a child in the house being attacked with croup. On the I6th the child who had returned home was attacked with diphtheritic croup and died on the 22nd, and the house was afterwards repapered, limewashed, and disinfected with sulphur. On the 2oth its brother was sent to Roxwell to his grandparents, and he remained there enjoying good health until July rst, when he was attacked with diphtheria. On June 25th it appears some clothes which had been in the room in which the younger child died were sent to Roxwell and worn by the patient, and this seemed the only possible way in which the child could have becom6 infected.*--From D r . ~hresh's 4 n n u a l Re#ort to the Chelmsford .R.S._/I. * For particulars of a case of diphtheria arising from infected rags after nine years, ~ee PUBLIC HEALTH, VoI. V.t p. 271.
267
THE PROBLEM OF HOUSING OF THE WORKING CLASSES IN R U R A L D I S T R I C T S . ~" ]~y GEORGE TURNER, M.B , D.P.H. Camb., M.O.H. Hefts Combined Districts.
IT appears a simple matter to condemn a house as unfit for human habitation and cause it to be closed. But it must be remembered that there are a certain number of persons in the district who must be housed, and must be housed too within a reasonable distance of their work, and that a cottage pulled down or closed is not necessarily rebuilt or repaired and made fit for habitation~ because the rent which an agricultural labourer can afford to pay does not make the erection of houses, such as would in these days be considered fit to live in, remunerative as a speculation. Cottages in the Hertford rural sanitary district, broadly speaking, are owned by two classes of people, viz., landowners who have built cottages for the convenience of their tenant farmers, and small owners who have invested their savings in cottage property as a source of income or perhaps as a provision for old age. Generally liltle trouble is experienced in dealing with the first class. Most ot the new cottages on the large estates are fit for anyone to live in, and, I should say, can yield little or no direct profit. Even when complaints are made with regard to the older cottages the complaints are usually attended to.
With the second class matters are far different ; the owners naturally expect to make money out of the buildings, which when originally bought were probably already far gone in ruin and on which little is spent in repairs. During the past twelve months I have m a d e house to house inspections of the district. The defects most usually discovered and reported were: General dilapidation due to ager rendering the cottage damp and unhealthy ; privies placed either against the house or too near to it ; newly-erected houses badly built ; bad or deficient supply of water. Sometimes the defects were such as to render the house unfit for human habitation without the possibility of any improvement short of demolition and reconstruction ; in other instances the cottages could be made habitable at a comparatively small cost, and the cases have been dealt with accordingly. I n the W a t t o n division of the Hertford Rural Sanitary District 22 houses were declared unfit for human habitation. Notices have in all cases been served on the owners, and the inspector's report states that : 4 houses were closed, 4 repaired, 2 partly repaired, 4 in hand, 5 the owners were waiting to make * From a special report to the Hertford R.S.A.