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ing disgusting mixture, and it is not, therefore, very surprising to be assured that such a well does not become dry even in summer. Unfortunately excrementitious liquids, especially after they have soaked through a few feet of porous soil, do not impair the palatability of the water; and this polluted liquid is consumed from year to year without a suspicion of its character, until the cesspool and well receive infected sewage, and then an outbreak of epidemic disease compels attention to the polluted water. Indeed, our acquaintance with a very large proportion of this class of potable waters has been made in consequence of the occurrence of severe outbreaks of typhoid fever amongst the persons using them.”

Norton's Abyssinian tube well is constructed by driving tubes into the soil, one length being screwed on to another, and the lowest segment having a series of perforations at the free end. When the subsoil water is reached, a pump is attached to the tube, and after pumping for some time, the water, which at first is dirty, becomes clear and remains so, as a cavity which corresponds to the ordinary well is formed at the end of the pipe owing to the gradual removal of the soil by pumping.

This is an excellent plan of obtaining a water-supply for villages situated on gravel, provided the water is not very far from the surface.

For precisely the same reasons as are stated above, it is equally necessary, in the case of deep wells, to protect the surface by carrying the impervious brickwork down as far as the impervious stratum. A very striking example of the effect of not doing so was met with some years ago in the Stafford Rural District, in the case of a deep well belonging to a school. The water in this case was highly polluted, so much so that it had a most offensive odour, and in the absence of any local insanitary surroundings, it was at first difficult to account for it; on opening the well, however, and introducing a light, the cause was at once apparent Down to a distance of 12 feet from the surface, the brickwork was perfectly clean, but at this point a well defined line was formed by the entrance of a filthy, slimy. looking fluid, which stained the bricks down to the water-level 50 or 60 feet below. In this case, the only source of pollution was from a manure heap in a farm yard 70 or 80 yards away, from which, no doubt, percolation had occurred through the surface gravel, along an impervious bed of clay. Had the brickwork of the well in question been built in an impervious manner down to this clay, no such pollution could have occurred.

The quality of cement used is very important, the best Portland cement being alone admissible for this, as for all sanitary work. The proportions of added sand ought, for this particular purpose, to be two of sand to one of cement, and the two ought to be thoroughly well mixed before the water is added. The sand selected must be clean and fine, and quite free from any dirt or clay, otherwise the cement will not set. Builders and workmen require careful watching as regards these points.

In all cases in which well-pollution is suspected, it is advisable to open the well in order to ascertain whether there is any evidence of the penetration of sewage matter above the water level. If such be the case, at one point or another, the brickwork, in place of presenting a clean, red surface, will be discoloured in a manner which, when once seen, will never be mistaken. Apart from this, it is highly desirable that wells shonld be opened periodically for the purpose of being cleansed, as, however well constructed they may be, with time impurity may arise.

Pumps.-There are two kinds of pumps, the ordinary suction pump and the forcing pump. The former will answer the purpose so long as the distance the water has to be raised does not exceed from 30 to 33 feet; in fact, as a rule, taking imperfections of mechanism into account, 25 feet may be looked upon as the limit. In the case of deeper wells, it is necessary to fix the more elaborate and expensive forcing pumps ; hence it is that in practice one so often finds open wells with a bucket and windlass for raising water. In such cases, the danger of surface pollution is increased, and if the arrangement be allowed to continue, as in the case of small cottages probably it will, the greatest care must be taken to see that the top of the well is so situated with regard to the surface as not to permit of drainage into it. A good fitting cover ought to be insisted upon, otherwise dead leaves and other decaying matter will find their way into the well.*

Cisterns.-In cases where cisterns are necessary certain precautions must be attended to in their construction.

(1) They should be constructed of a material that will not impart any injurious quality to the water. Galvanised iron and slate both answer the purpose well; the latter, however, although the best in other respects, is heavy and it is difficult to avoid leakage through the joints; these should be carefully made with cement. Lead and wood are bad materials for use in the construction of cisterns. The risk of metallic contamination in the case of the

* For a full and simple description of the construction of pumps see Well Sinking, Weale's Rudimentary Series.

former has often been demonstrated, and, as regards the latter, sooner or later decay takes place and organic contamination results.

(2) They should be easily accessible, and, while the sun's rays ought to be excluded, the place where they are fixed must not be dark. These requirements are essential so as to afford every facility for inspection and cleansing. It is not unusual to find cisterns placed under floors, in situations quite unknown to the occupants of the house, until, by reason of the foul condition of the water, a search is made, and the cause, in the shape of dead and decomposing rats, is discovered.

(3) They ought to be covered in and ventilated, otherwise dirt of all descriptions will enter.

(4) The overflow pipe ought to be carried to the outside where it should either be cut short or discharge on to an open gully. It used to be a common practice to connect it direct with the soil pipe or drain, in which case it simply acts as a ventilator, and foul gases are conducted direct to the drinking water. In some instances in which this is done a syphon trap is introduced, but as the overflow pipe is only in 11se when the ball-tap which regulates the supply of water is out of order, this trap owing to evaporation must stand empty, and, therefore, be absolutely useless. Some years ago the author found an illustration of this fault in the case of an hospital, where, to make matters still worse, the cistern overflow pipe was connected direct with the drain from the fever wards.

(5) The supply pipe for the water-closet must not pass direct from the cistern, but a smaller cistern (water waste preventer) ought to be interposed (see p. 103).

Distribution.-In public water-supplies there are two systems of distribution—the constant and the intermittent. The former is very much the better, for a variety of reasons, although the latter is the system in operation in some towns.

Constant and Intermittent Systems.-In the case of the constant system, the taps of the houses deliver water direct from the service pipes, without the intervention of a cistern, except in the case of water-closets, which have what are termed "water waste preventers”_small cisterns that deliver, at one time, only the requisite quantity of water for flushing purposesand kitchen boilers, which cannot be supplied direct, but must be provided with small supply cisterns. The necessity for having large cisterns for storing water on the premises is thus avoided, while, with an intermittent supply, these are essential, otherwise, from time to time, houses woulâ be entirely without any

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water. The chief objection to the storage of water in houses is the danger of pollution, which may occur from various causes already noticed. Another objection to the intermittent system is that, by periodically shutting off the water from the mains, a vacuum is liable to be created in the pipes, from gradual leakage at faulty joints, and this vacuum is replaced by foul air, or even sewage, from leaking drains, an occurrence which in more than one instance has led to an outbreak of typhoid fever. The mains, in the case of a constant supply, are always full, therefore this risk is to a large extent avoided. In addition to this, pipes running full are less liable to rust than those that are occasionally empty, as air in the presence of moisture has considerable corroding power.

Besides these advantages, in the constant system there is always an abundant supply of water in the of fire. The disadvantage of a constant supply is that the waste from leaking pipes is greater, as the water is always at pressure in the mains; also, by reason of the great pressure in the service pipes, the various fittings must be of more perfect make, and therefore more costly. For this reason, much waste of water has resulted in cases in which a constant has been substituted for an intermittent supply without replacing the old fittings. On the other hand, in some cases where the change has been made, and the necessary fittings substituted, a diminution in waste has resulted.

Charges. The system of charges for water may be by rate or by meter. The former is much the better for domestic supplies, as, by making a charge in accordance with the quantity consumed, an inducement is offered to economise, and economy in the legitimate use of water is certainly not what one would wish to see.

Indirectly, there is another important reason for placing no obstacle in the way of a generous use of water, and that is the cleansing effect that it has on the drains and sewers. By limiting the supply, we diminish the flushing power, and thus add to the risk of deposit, which is so highly objectionable as will be explained in a later Chapter. Of course, in special cases, such as manufactories, it may be necessary to charge by meter.

Pipes.-Iron, with a coating of some protective material, such as Angus Smith’s varnish, is what is used for mains. Lead is most generally used for house pipes, but in the case of certain waters its use is dangerous, for reasons already stated. Galvanised iron pipes are now often used, as they are not so liable to rust as plain iron pipes. The temptation to use lead pipes is

some.

very great, as they can be carried anywhere round corners by simply bending them; whereas in the case of iron pipes, joints have to be inserted at frequent intervals, not only where angles have to be passed, but also where one length has to be joined on to another.

Many materials have been suggested as a protective coating for both lead and iron pipes, but most are either unsatisfactory or too expensive for general use.

Glass-lined iron pipes are manufactured, and answer the purpose well.

Tin is used as a protective coating for both iron and lead pipes, but in this form it is hardly satisfactory.

Composite pipes, consisting of a block tin pipe enclosed in a lead pipe and solidly united together, are not so liable to be acted upon by water, and they may be bent in any direction like an ordinary lead pipe; these answer excellently. Iron pipes treated by the Barff process are recommended by

The process consists in raising the temperature of the pipes to a white heat (about 1200° F.) in a chamber into which superheated steam is passed. After being exposed to the action of the steam for several hours the metal becomes coated with a protective oxide.

Impurities. The chief impurity, indeed almost the only one that need be considered from an inspector's point of view, is that which comes from an organic source, either vegetable or animal, the latter being much the more objectionable of the two.

Both may be present in a solid form or in solution; in the former case, the water is distinctly discoloured, the colour vary. ing in depth in accordance with the amount or nature of the contaminating material; while in the latter, notwithstanding the presence of considerable impurity, the water may be perfectly clear and wholesome looking The absence of colour, therefore, is no sign that the water is pure; but neither is its presence a sign of dangerous pollution, for peat imparts a considerable colour to water which need not be injurious. The important point to remember is, that a clear water need not mean a pure water, but that danger may exist eren though it is beautifully sparkling and perfectly clear. Here, then, we are brought face to lace with a problem which can only be solved by the chemist and bacteriologist, but as the inspector ought to appreciate the significance of the question, we must go a step farther, and explain shortly the reason why water which contains organic matter is dangerous from a health point of view.

Presence of Organic Matter-What it means.- In the

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