Recent Modifications in Sanitary Drainage
IT is only about four years since I published in these pages a series of papers on The Sanitary Drainage of Houses and Towns. So far as possible, I therein stated fairly the condition of the art at that time. Viewed in the light of present knowledge on the subject, those papers are already, in many respects, quite out of date. Knowledge has increased, experience has multiplied, and invention has been most fertile. The illustrations then given of the arrangement of house drainage represented a soil-pipe and drain running in an unbroken course from the sewer in the street, under the basement floor, and up through the roof of the house. Connected with it were several water-closets, a sink, and the overflow-pipes of the tank in the attic and of the service cisterns of the closets. In all cases the different vessels were separated from the soil-pipe only by water-sealed traps, and only the same protection was afforded in the case of the main tank. The system thus represented is defective in several particulars.
(a.) The water of the tank is liable to dangerous contamination through the overflow-pipe which leads into the soilpipe, with only the insufficient protection of a water-seal, — especially insufficient as it has no certain means of renewal, and may by evaporation give direct access to the air of the soil-pipe.
(b.) The overflow-pipes of the service cisterns may readily become channels for the introduction of drain air to the apartments.
(c.) The unprotected traps of the sink and the water-closets are inadequate for the work they are intended to perform, and all of them are susceptible, under certain conditions, of becoming empty by evaporation or by siphoning.
(d.) Although the soil-pipe is continued through the roof, full-bore, and is open at the top, it has no provision for the admission of fresh air at its foot, which is now regarded as a matter of imperative necessity. These defects are sufficient, in the opinion of those instructed in such matters, to condemn this whole arrangement, which only four years ago was regarded as the best yet devised.1
All this indicates that the art under consideration is undergoing rapid development, and that it is by no means to be assumed that we have yet arrived at ultimate perfection in the matter.
Were I called upon to-day to specify the essential features of perfect house drainage, I should include the following items: —
The establishment of a complete circulation in the main line of soil-pipe and drain, allowing a free movement of atmospheric air through the whole system from end to end, together with as complete a circulation through minor pipes as could conveniently be secured.
The complete separation of the overflow of every tank or cistern delivering water for the general supply of the house from any soil-pipe or drain containing a foul atmosphere.
The supplementing of every watertrap with a suitable mechanical valve, to prevent the water of the trap from coming in contact with the air of the drain.
The reduction of the size of all wastepipes, and especially of all traps, to the smallest diameter adequate to their work.
The abolition of all brick or earthenware drains within the walls of the house, using in their stead the best quality of iron pipe, with securely caulked lead joints.
The substitution, so far as practicable, of wrought-iron pipes for lead pipes, in the case of all minor wastes.
The coating of all iron pipes, both cast and wrought, inside and out, with “ American ” enamel, a glossy black coating which withstands in the most complete manner the chemical action and changes of temperature to which it is subjected in such use.
The iron pipes should be extended so far beyond the foundation of the house as to obviate the opening of joints by settlement, so common where earthenware drains are subjected to a slight movement of the foundation, or of the new filling about it.
The object to be sought is the provision of a permanent drainage channel for the removal of all wastes, offering little asperity for the adhesion of foul matter, swept from end to end by fresh air, absolutely separated by mechanical obstructions from the interior atmosphere of the house, and literally a section of out-of-doors brought for convenience within the walls of the house, open to receive the contents of the various waste-pipes leading to it, but securely closed against the return of its air. I. believe that the next step in advance will be the establishment of means by which the whole length of this drainage channel may be thoroughly flushed with clean water at least once in twenty-four hours.
As a prominent detail of house-drainage work, the long-accepted water-closet is being made the object of important modifications. The stereotyped article, the “ pan ” closet, has little to recommend it beyond the fact of its general adoption. It is faulty in principle, in arrangement, and in construction. While it is cleanly to look at, and lends itself readily to ornamental joinery, it has defects which should drive it out of existence. Deep down in its dark and hidden recesses, where only the ken of the plumber ever reaches, a large and sluggish trap — they call it a “cesspool” in Scotland—is generally holding the filthiest filth in a State of offensive putrefaction. The iron chamber above this is lined with the foulest smear and slime, constantly producing fœtid and dangerous gases. The earthenware bowl which surmounts this is set in putty, which yields to corrosion and to the jar of frequent use, until it leaks foul air, often in perceptible quantity. The panful of sealing water soon becomes saturated with foul gases, which exhale thence into the house. The whole apparatus is incoffined in tight-fitting carpentry, which shuts in the leakings and the spatterings and their vapors from the free access of air, boxing up in the interior of the house, and generally in free communication with the spaces between the walls and under the floors, an atmosphere heavy with the products of organic decomposition, and faintly suggestive to the unwonted nostril of the mus decumanus defunctus.
Some of these defects were recognized and pointed out in my earlier papers. I then believed that the difficulties of the case had been solved in great measure by the Jennings closet. It now seems that this closet and the whole class to which it belongs are seriously defective; and, in the absence of anything better, I am disposed to go back to the simple “ hopper ” closet, such as is used in the cheapest work, and to depend on frequent and copious flushing to keep it clean. This closet has the great advantage that its only trap is in sight at the bottom of its pot. There is no inner " chamber of horrors” concealed by a cleanly exterior.
I have recently used a number of these closets supplied with various sorts of apparatus for periodical flushing, and I find that wherever a half-gallon flush can be given every ten or fifteen minutes they are kept perfectly clean. I have no doubt that flushing every twenty minutes, or perhaps at longer intervals, would keep them free from all sanitary objection. This would require a supply of about fifty gallons per diem.
Recent invention has been turned in the direction of the provision of mechanical appliances for separating the trapping water from the air of the soilpipe or drain. There are several devices which accomplish this purpose, — one of them my own, and more than one of them constituting a very great improvement upon, and indeed an absolute step in advance of, anything in use five years ago.
Another most important matter of recent development is the thorough and through ventilation of soil-pipes. Formerly the soil-pipe invariably stopped at the highest closet of the house. When the danger of pressure came to be understood, it was considered imperative in all work of the best class to carry a vent-pipe out through the top of the house. As this pipe, from the smallness of its size and from the irregularities of its course, had but limited capacity of discharge, the necessity was quite generally recognized for carrying up the soil-pipe itself, full-bore, through and above the roof. This was the point reached at the time of my earlier writing. It soon became evident that even this large extension of the pipe afforded no real ventilation. A deep mine shaft cannot be ventilated by simply uncovering its top. No complete frequent change of air can be effected in a soilpipe by merely opening its upper end. Air must be introduced at the bottom to take the place of that which is discharged at the top. It is now considered imperative in all good work to open the soil-pipe at both ends, or at least to furnish the lower part of the pipe with a sufficient fresh - air inlet to effect a thorough ventilation of the whole channel.
We have heard so much of “sewer gas ” that we were in danger of ascribing the production of this foul air only to the sewer and cess-pool. Indeed, the majority of sanitarians to this day seem to believe that if they can effect a thorough disconnection between the sewer or drain and the waste-pipes of the house they have gained a sufficient protection against sewer gas. The fact is that that combination of the gaseous products of organic decomposition which is known by the generic name of sewer gas is very largely produced by the contents of the house-pipes themselves. Not only in the traps, where the coarser matters accumulate, but all along the walls of the smeared pipes, where filth has attached itself in its passage, there is a constant decomposition going on which is producing its constant results. The character of this decomposition and the character of the produced gases are greatly influenced by the degree to which access is given to atmospheric air. The more complete the ventilation, the greater the dilution of the gases formed and the more complete their removal, and also the more innocuous their character. Under the most favorable circumstances, the contained air of a soil-pipe must be offensive, and is likely to become dangerous; so that, however thorough the ventilation, we must still adopt every safeguard against its admission into the house. The facility with which foul gases penetrate water and escape from it makes the water-seal trap, which is now our almost universal reliance, an extremely inefficient protection. There can be no real safety short of the adoption of some appliance which shall keep every outlet securely closed against the possible return of drain air.
Mr. Elliot C. Clarke, the principal assistant engineer in charge of the improved sewerage work of Boston, in a paper entitled Common Defects in House Drains, contributed to the Tenth Annual Report of the Massachusetts State Board of Health, says on the subject of sewer gas: “ The writer has no wish to be an alarmist. The risk from sewer gas is probably not so great as many suppose; it is a slight risk, but a slight risk of a terrible danger. If a man thinks there is no need of insuring his house because his father lived in it for fifty years without a conflagration, he has a right to his opinion.” Professor Fleeming Jenkin, in his Healthy Houses, says, “ Simple sewer gas is little worse than a bad smell. Tainted sewer gas may be so poisonous that a very little introduced into a bedroom—so little as to be quite imperceptible to the nose — shall certainly give typhoid fever to a person sleeping there. The germ is a spark, the effects of which may be unlimited. We do not content ourselves with excluding the great majority of sparks from a powder magazine; we do our best that not one may enter.”
While the water seal is very defective in itself, it is a very important adjunct to any mechanical means of separation that may be adopted, and all necessary precautions should be taken to prevent its removal by “ siphoning,” — the sucking out of the water by the partial vacuum caused by the flow of water in the main pipe, to which its outlet leads. To prevent this siphoning action often taxes the ingenuity of the engineer more than any other part of house-draining work; and until special devices are made to meet the exigency this must remain the most difficult and intricate part of the house drainer’s task.
Any one whose attention is given to sanitary work must be more and more struck with that peculiarity of human nature which assures us of the exceptional excellence of our own belongings. I have rarely been called to examine the drainage of a house without being told that I was sent for merely as a matter of extra precaution. I have never completed any examination without discovering serious sanitary defects, — not merely such errors of arrangement as were universal until a short time ago, but actual, palpable bad condition, which the owner and his plumber at once acknowledged as of a grave character. Leaks in drains under the cellar floor, or in or near the foundation; lead wastepipes eaten through by rats, and spilling their flow under the house ; lead soilpipes perforated by corrosion; imperfect joints leaking drain air within the partitions ; the accumulation of dirty sloppings under the bench of the watercloset; and even untrapped connection between some room and the soil-pipe, or the direct pollution of the air over the tank through its overflow-pipe, —these are most common faults, and some one of them I have found to exist wherever I have looked for them in a “first-class ” house, where it was naturally supposed that the most perfect conditions prevailed.
In no department of sanitary work has the progress been more marked than in the improvement foreshadowed in my former paper on House Drainage concerning the disposal of the liquid wastes of country houses by the process of subsurface irrigation. Like all radical improvements, it has had its share of prejudice to overcome, and it by no means found the professional public ready to accept it as the demonstrated success which English experience had shown it to be. It is now quite safe to say that, among all engineers and architects who have given attention to the matter, it is acknowledged to afford the best solution yet attained of this most difficult problem. I know very many cases of its adoption, often without professional guidance and carried out in a rule-of-thumb sort of way, and I have heard of none that is not satisfactory. It does away with that king of nuisances, the cesspool, and disposes of all manner of liquid waste insensibly, completely, and safely. The credit for this improvement is due primarily to the Rev. Henry Moule, the inventor of the earth-closet, and hardly less to Mr. Rogers Field, C. E., who relieved it of its chief embarrassment by adapting to it his automatic flush tank. This system has recently received the unqualified indorsement of that highest American sanitary authority, the Massachusetts State Board of Health, which in a circular issued in April, 1879, says, “ Chamber slops, and slop water generally, should never be thrown on the ground near houses. They may be . . . used by distribution under the surface of the soil in the manner described on page 334 of the Seventh Annual Report of the State Board of Health, and now introduced in the town of Lenox, Massachusetts. ... If water-closets are used, and there are no sewers, the best disposal of the sewage is by the flush tank and irrigation under the surface of the soil, as described on page 135 of the Eighth Annual Report of the State Board of Health.”
This system has been in full operation for the entire sewage of the village of Lenox, where it has proved itself an absolute and unquestionable success. The question which seems to arise in every Northern mind when this method is suggested relates to the possible effect of severe frosts. It seems now to be clearly demonstrated that this consideration may be left entirely out of the account, no instance having been cited of the least obstruction from this source. This point will be more fully treated further.
The progress made in the matter of town drainage has not been less than that in the twin department of house drainage; but the advance has been thus far — at least so far as this country is concerned — more a matter of theory than of practical application, and it relates more to villages and to what may be called village - cities than to larger places, like New York, Boston, and Philadelphia.
Sewerage was long confined to large towns, and it reached its development under the direction of engineers trained to foresee all possible contingencies, and to pitch their work on a scale adequate to cope with them. With usually ample means at their command, and with the inclination to work after great models, their works have generally been costly and vastly comprehensive. So far as the drainage of great cities is concerned, there is much to be said in favor of their practice. There is much to be said, too, on the other side, and it has been ably said. My present purpose relates chiefly to the sewerage of villages and country towns having a considerable proportion of uncovered and unpaved area. There are hundreds of towns in this country which cannot afford the gigantic and costly work of introducing such a system of sewers as it is usual to find in a great city. Quite generally, when the question of their drainage arises, a city sewerage engineer is consulted, and a plan is prepared which remains unexecuted because of its excessive cost. By far the larger part of this cost is due to the fact that the proposed system contemplates the drainage of such sub-cellars as are rarely found in country towns, involving a depth that would probably never be needed, and the removal of the storm water, which, after the area shall have become covered and paved, might flow off by the public sewers. It would be better, in the case of all rural towns, to disregard the question of storm water entirely. This may be more safely and much more cheaply removed over the surface. The only reason for admitting it to the sewers would be to prevent injury to property, and, under the circumstances we are considering, the danger of this is not sufficient to justify the expense, nor is it sufficient, were there no question of expense, to justify the sanitary and economical disadvantages of providing for it by a system of large sewers. It is better to keep above ground, and to discharge by the natural means of outflow, all water which may be so disposed of without offense or danger to health, — that is, all or nearly all rainfall. The extent to which the first flow over a paved road-way may properly be admitted to the sewers is a question to be decided according to the circumstances of each case. It is generally wiser to keep such road-ways clean by sweeping than to use the rain-fall as a scavenger.
What towns of the class under consideration need — and they need it very imperatively — is a perfect means for the removal of the foul wastes of households, factories, etc., and the draining of the sub-soil, if this is springy or wet. They should only be called upon to spend the money necessary to secure these ends; and if they can learn to limit their demands to this absolute requirement, their sanitary improvement need no longer be the bugbear that it now is.
The advantages of small-pipe sewers have been sufficiently stated, except, perhaps, with reference to the single matter of ventilation. It is much easier and more simple to secure the needed change of the atmosphere of a small chamber than of a large one, and the usual means, which are but partially effective in the case of a large brick sewer, are ample for the complete ventilation of a small pipe. Hitherto the objection has held, in the case of pipe sewers of less than ten inches in diameter, that when they become obstructed it is a difficult and costly matter to clear them. But for this objection, there was no reason why six-inch sewers might not be used for all villages or parts of towns having a population of not more than one thousand; for a six-inch pipe laid even with a very slight inclination has ample capacity for the discharge of all the household waste of such a population.
We have now reached the point where there is no reason whatever to apprehend the obstruction of such a sewer by anything that can get into it through proper and properly arranged branch drains. Rogers Field’s flush tank, as arranged for the periodic flushing of such sewers, may be confidently relied on to keep them swept clean of everything that may enter them. The accompanying diagram shows the construction of the annular siphon which is the essential feature of this tank. A siphon of this form, four inches in diameter, comes into action with certainty under a stream of one tenth of a gallon per minute; so that a tank having a capacity of one hundred and fifty gallons, placed at the head of each branch sewer and fed by a stream which will fill it once in twen-_ ty-four hours, will give it a thorough and daily llushing, and keep it
clear of all obstructions. No matter how limited the public water supply may be, this small amount can always be spared for the work. Where there is no public supply and no available extrinsic source of flushing water, the sewage itself from a few of the upper houses along each lateral sewer may be collected in the tank and used for the flush.
This simple device has proved itself, both here and in England, to be entirely reliable and effective. It may safely be assumed that it has secured a reduction of the cost of the drainage of small towns to one half of what was formerly necessary.
It has been held hitherto to be one of the advantages of sewerage that the imperfect joints or imperfect material of the sewers afford an outlet for superabundant soil water, and secure a valuable sub-soil drainage. It is coming to be understood that the same channels which admit soil water to the drain will admit drain water to the soil, robbing the sewers of the vehicle needed for the transportation of their more solid contents, and causing a dangerous pollution of the ground, of cellars, and of drinking-water wells. The foul - water sewers should be as absolutely tight as the best material and the best workmanship can make them, and the drainage of the ground should be effected by the use of agricultural drain tiles, constituting an entirely separate system, which, while they may for economy’s sake generally occupy the same trenches with the sewers, should be carefully arranged to prevent sewage matters from entering them.
The question of sewage disposal is the great unanswered question of the day. We are familiar with the objections to the methods usual here. European countries, which have been forced by the density of their population to give especial attention to this subject, have as yet hardly got beyond the point of proving that there is no royal road to success, and that whatever theory may say on the subject, sewage not only lias no value to the community producing it, but it cannot be got rid of except at considerable cost.
The only method thus far developed which is entitled to consideration here, aside from discharge into the sea or into a running stream, is purification by application to the soil, with or without the agricultural consideration. Whether by surface irrigation, by the use of sub-surface absorption drains, or by intermittent downward filtration, this method of its disposition, properly applied, is absolutely complete and satisfactory. The opinion has quite naturally prevailed that the severity of our winter climate debarred us from availing ourselves of it. The experience of the past severe winter has fully justified the opinion of those who have maintained that this objection is not a real one. In England the sewage-irrigation farms have taken charge of the dflluent without interruption throughout a season of almost unexampled severity. At Berlin a like immunity has continued throughout the winter ; and even at Dantzic, near the mouth of the Vistula, in a climate nearly as severe as that of St. Petersburg, and where provision was made for a direct discharge into the river during the winter season, the disposal by irrigation is said, to the surprise of all, to continue uninterrupted in the coldest weather.
At the Nursery and Child’s Hospital on Staten Island, winter overtook us before our absorption drains could be laid. The flush tank, which holds one day’s sewage, was made to discharge over a low spot near the absorption ground. Even in the coldest weather the entire outflow settled away into the earth before the next flood was delivered. Evidently the warmth of the sewage is in all cases sufficient for it to thaw its way into the ground. This is, without doubt, the explanation of the continued working of the shallow drains under my own lawn during nine consecutive winters, although at least once the ground was frozen to a depth of two and a half feet below them.
George E. Waring, Jr.