CHAPTER VIII. WATER SUPPLY. (Part 2)

water^ The colour will turn yellow if lead be present; it will also turn yellow if barium be present. This in- gredient is both rare and harmless; it is not likely to be met with. Both tests indicating lead as above, it may fairly be taken as probable that the water is contaminated by lead. Take sulphuric acid, and add six drops to a small glass of water; it will give a white precipitate if lead be present, soluble in caustic potash. Lead steeped for some hours in water, even in distilled or pure water, which naturally attacks lead, will not give a sufficient quantity of lead in solution to show any effect from chemical reagents to a class in the lecture-room, un- less you evaporate the water to about one-twentieth of its bulk. But it should not be foi-gotten that the effects of lead poisoning are cumulative; they remain in the system and accumulate there. Sir Charles A. Cameron on one occasion desired a delicate test to detect lead in the water contained in a lead cistern. All ordinary tests failed, so he plsu^ed some small fishes in the water and watched their movements. After some time their bodies became cramped into a curve, so that they could no longer swim in straight lines, and when darting at their food they invariably missed the mark, owing to this effect of the lead poisoning; the fishes passed such quantities of the water through their gills that the cumulative effect of the poison was made apparent. The presence of chlorine (chloride of sodium, or salt) in well waters, found in inland places where natural deposits of salt do not exist, is almost certain proof of sewage contamination. 378 DOMESTIC SANITARY DRAINAGE AND PLUMBING. Waters of this class can be detected by nitrate of silver, which throws down a white deposit. Add a little ammonia, and the white deposit vanishes, for it is soluble in ammonia. Of course the presence of salt or chlorine in well waters near the sea cannot be taken to prove sewage contamination. For zinc impurity (sulphate of zinc) — Take ferrocyanide of potassium, and add six drops to a small glass of the water. The colour will turn green if zinc be present. And, again — Take sulphide of ammonium, and add six drops to another small glass of the water. The colour will turn white by a white precipitate falling. For copper impurity (copper chloride, blue vitriol) — Take common ammonia, and add eight drops to a small glass of the water. The colour will turn light and dark blue if copper be present ; or bright steel dipped in copper-tainted water will turn copper coloured. Take ferrocyanide of potassium, and add eight drops to a small glass of the water. The water will turn chocolate colour if copper be present. For iron impurity (chloride of iron) — Take ferrocyanide of potassium, and add twelve drops to a small glass of the water. The colour of dark Prussian blue will appear if iron is present. Let me again repeat that the definitive, decisive testing of potable waters is and should remain beyond the scope of plumber's work. WATER SUPPLY. 379 The physical characteristics of good water may form some guide to a decision on its quality. It should be clear, without sediment or suspended particles ; colourless, or slightly bluish if deep, yellow or brown water being suspicious, unless coloured by peat or iron ; bright and sparkling, full of air and carbonic acid ; pleasant to taste, not brackish, free from odour, and dissolving soap easily. These qualities should appear in wholesome waters, and render the chances of its really being so very favourable. This will be the proper place in which to refer to the action of water on the metals used in pipes and tanks, lead and zinc. Very small quantities of lead are sufficient, if repeatedly taken, to produce symptoms of poisoning. One-tenth of a grain per gallon is enough to affect most persons injuriously. The purest waters, and those most aerated, unless contain- ing a large amount of carbonic acid gas, have the greatest effect on lead. The Dublin Vartry water and Glasgow Katrine waters are very pure and attack lead. Again, water containing animal organic impurities, or con- taining nitrites or nitrates or chlorides, will attack lead. But waters containing carbonates, chalk and lime waters, and, in a less degree, sulphates and phosphates, form a film on the metal which prevents further corrosion. Sir Charles Cameron, the distinguished Chief Medical Officer of Health for Dublin, found that lead pipes and sheets, if alloyed with three per cent, of tin, were rendered proof againsf all lead action of the Dublin soft waters, and this alloyed lead pipe has been adopted and used for many years with safety. Lead is specially liable to corrosion when attacked by water and air alternately, and this fact applies to. all metals 380 DOMESTIC SANITARY DRAINAGE AND PLUMBING. which are corroded by water. Cisterns oftener give way when repeatedly filled and emptied from an aerating supply under pressure. The water should, therefore, always be maintained at one level in lead-lined cisterns. In cases also where waters are of a character likely to corrode lead. Dr. Christison recommended that the cistern be filled first with a weak solution of phosphate of soda, by which an insoluble protective film is formed on the lead. Many kinds of spring and deep-well waters may be quite safely stored in lead cisterns and distributed in lead pipes. The chemical analyst should be employed to test the character of waters in the country before using lead extensively in contact with it. Plumbers should gather the practical lesson from these statements that lead-lined covers should never be used for cisterns, especially for hot-water cisterns. The watery vapour or steam condenses on the lead, and with the combined action of the air rapidly corrodes the lead, and the water, dropping back into the cistern, carries with it measurable quantities of lead. Hot water acts strongly on lead, especially if distilled through lead pipes. It is dangerous, therefore, to use hot water for cooking purposes which has been circulating through leaden pipes and into leaden cisterns. Composition lead pipes, used for gas and composed of scrap lead and antimonial lead, should never be employed to carry drinking water, hot or cold ; it is a very dangerous practice. Tin-lined lead pipes were recommended by many author- ities, but have practical objections of their own, "being difi&cult to bend and to joint satisfactorily. The action of water upon lead is so frequently prevented or neutralised by the salts in solution in most waters, that the startling statements we see made must be somewhat WATER SUPPLY. 381 exaggerated. Care, however, should always be exercised to prevent all evil consequences. Zinc dissolves in water at ordinary temperatures, especially in distilled waters, rain-waters, and waters containing car- bonic acid. Hard waters, in which are salts of lime, exert but a slight action on zinc, which amounts to the simple deposit on the zinc of an insoluble film of hydrocarbonate of zinc, which stops further corrosion. Authorities differ as to the extent of the injury caused to the system by zinc poisoning. But, on the report of a French Government commission appointed to inquire into the subject, the use of zinc-coated iron water tanks was pro- hibited in the French navy ; and this decision is supported by many experiments on water passed through galvanised- iron piping by Dr. Frankland, Professor Heaton, and many others, with results showing very marked presence of zinc in the water. In galvanised-iron cisterns and pipes the iron is coated with zinc, and to some extent alloyed with it — the two metals form a galvanic couple — so that, under the action of any exciting liquid, the zinc is attacked while the iron is protected. We have all seen also how the zinc will scale off in cisterns, and how often the oxidation or rust of the iron comes through. So much so, that galvanising iron laimdry boilers is of little use in preventing rust to clothes boiled in them, and hot cylinders and tanks are frequently found coated with rust inside, as if they had not been galvanised at all. The rust is sometimes transported to the cisterns from the iron boilers, but frequently it breaks out in the cisterns. Zinc as a poison is very dangerous ; therefore the use of it in vessels for water or food is open to grave question, and, 382 DOMESTIC SANITARY DRAINAGE AND PLUMBING. as in the case of lead, precautions should be taken to ascer- tain the quantity of water you bring in contact with zinc or zinc-coated iron. Water for drinking ought not to be allowed to stand long in zinc or galvanised vessels. Sometimes the zinc is taken up by the water to such an extent that a disagreeable metallic taste is imparted to it. The following statement, made by F. P. Venable, Ph.D., in the Jmn^tud of the American Chemical Soeieiyy is worthy of production here : — " The increase in tlie use of galvanised iron, especially in the form of water tanks and pipes, has led to a reopening of the question as to the possible injurious effects from the use of such water. It is a matter of importance, then, to us how far our knowledge extends on this subject, and I will collect here all of the known facts, so far as I have been able to get at them. The so-called galvanised iron is, of course, nothing more than iron dipped in a bath of zinc, and so superficially coated with it, and, to a certain extent, alloyed witli it. The character of the protection afforded the iron is galvanic (hence the name), the two metals form- ing a galvanic couple, so that under the action of any ex- citing liquid, the zinc, and not the iron, is attacked. "That zinc dissolves in potable water has long been shown by the experiments of Boutigny, SchaueffMe, and Langonn(5. Distilled water and rain-water dissolve it more readily than hard water. Especially is water containing carbonic acid capable of this solvent action. So much may be taken up that the water becomes opalescent, and acquires a distinctly metallic taste. It seems that, by the action of water, hydrate and carbonate of zinc are gradually formed, and that this action is more rapid in the presence of certain saline matters, but is weakened by the presence of calcium salts. WATER SUPPLY. 383 "As to the injurious effect of such water, authorities diflFer. Fonssagrives has investigated the question, consult- ing the statistics of the French navy and the recorded ex- periments of others, adding, however, none of his own. The French Government had, before this, appointed a committee to make a special report on the subject, and the investiga- tions of Eoux, in 1865 and 1866, furnish evidence enough of possible injury to health from water stored in galvanised- iron tanks to lead to an order from the Minister of Marine prohibiting the use of such tanks on board ships of war. Boutigny attributed grave effects to the use of these zinc- containing waters, looking upon it as probably resulting in epilepsy. Fonssagrives, however, maintains that the zinc is not cumulative, and produces no bad effects unless taken in large doses. Doubt is thrown on this position, however, by the fact that his assertions as to the limited solubility of zinc in ordinary drinking water are not sustained by experiments. Without doubt such waters have been used for considerable length of time, and no injurious effects have been noticed. This may have been due, however, to the hardness of the water, and hence the small amount of zinc dissolved. Pappenheim states, in contradiction to the assertion of Fonssagrives, that zinc vessels are dangerous and must be carefully avoided. Dr. Osborne, of Bitteme, has frequently observed injurious effects from the use of waters impregnated with zinc. Dr. Stevenson has noticed the solvent action of water on galvanised iron, and states that probably its continued use would cause injury to health. He recommends as a convenient test for the presence of zinc in potable waters, the addition of potassium ferro- cyanide to the filtered and acidulated water. Zinc gives a faint white cloud or a heaver precipitate when more is present. Dr. Frankland mentions a case of zinc poisoning where well water, containing much dissolved oxygen and 384 DOMESTIC SANITARY DRAINAGE AND PLUMBING. but little carbonic acid, was used after passing through galvanised-iron pipes. Professor Heaton has recorded the analysis of spring water in Wales, and a second analysis of the same water, after passing through half a mile of galvanised-iron pipe, showing that the water had taken up 641 grains of zinc carbonate per gallon. A similar instance of zinc-impregnated water has come under my own observa- tion, and I append the analytical results. The water from a spring two hundred yards distant was brought by galvanised- iron pipes to a dwelling-house and there stored in a zinc- lined tank, which was painted with white lead. The water became somewhat turbid and metallic-tasting, and its use for drinking purposes was discontinued. Analyses were made after the pipes had been in use about a year. A somewhat full analysis of the spring water was made under my direction by Mr. J. C. Eoberts. The analyses of water from the tank, and directly from the pipe, I carried out only so far as zinc, iron, and tests for lead were concerned. The results are calculated in grains per gallon of 231 cubic inches. astituents oi the water : — Grains. Silica . . ... 2-46 Lime •28 Magnesia •17 Alkalies . •48 Chlorine •35 Sulphuric acid . -19 Carbon dioxide (calculated) . •45 Total residue on evai>oration . 4-34 "The tank contained 448 grains of zinc carbonate per gallon, with a trace of iron, and no lead. Water from the pipe gave 4'29 grains of zinc carbonate per gallon and a trace of iron. "It is evident, then, when the dangerous nature of zinc 8^s a poison is taken into consideration, that the use of ziac- WATER SUPPLY. 385 coated vessels in connection with water, or any food-liquid, should be avoided." But notwithstanding all this condemnation, galvanised- iron pipes and cisterns are and will continue to be generally used. Copper is a metal strongly attacked by water, and copper exerts a poisonous action on the human system. Chlorides, as common salt, and ammonia compounds in water increase its action on copper, but sewage and urine are specially powerful in corroding copper pipes, etc., in contact with it. Copper is therefore a highly unsuitable material for soil- pipes and waste-pipes. Pure water has also a distinct action on copper, even if in contact with it for an hour or two. Copper should therefore always be well tinned when used in cisterns or pipes ; indeed, well-tinned copper is the best and safest material for hot-water pipes and for soft- water tanks and pipes. Tin is not injuriously attacked by water, and, but for its great expense, perhaps pure tin would be the best of all metals in cisterns and pipes for storage and distribution of pure water. The quantity of water required for every person is set down at various amounts by diflferent authorities. A flat sponge-bath would catch more rain-water in twelve months than an ordinary man could drink in that time, so that a famine of water need never be feared in these countries. Plumbers, in providing supplies for households, whether from rainfall or otherwise, should aim st twenty gallons per head per day, and as much more as can be readily obtained. Money is well spent when it can be spared in securing a supply of water to a house or to a city — not merely abundant, but superabundant. 2 c 386 DOMESTIC SANITARY DRAINAGE AND PLUMBING. The sources of supply are— 1. Public water supply, which is generally the best of all. 2. Eainfall on roofs, intercepted and collected by simple gravitation in high-level tanks, can \ye distributed by gravitation also, thus saving all pumping labour. Water carefully collected and stored from such a source ought to be fairly good. 3. Eainfall on yard surface and on low or distant roofs, collected and conveyed by underground pipes to underground tanks, whence it may be pumped to the high-level cisterns, or, better still, be reserved for supply to laundry, garden, etc., on lower levels, and not used for drinking or cooking. 4. Pure streams, free Fig. 341. — Filtering arrangement at head of water supply for river water. ^ from sewage contamination or cattle fouling, especially if running at a level and above the house, may by gravita- tion yield a constant safe supply, through proper filtering arrangements, for all household purposes save drinking. 5. Springs. 6. Deep wells ; and 7. Shallow wells. The best and simplest filtering arrangement for large supply consists of two tanks, one over the other, with a ball tap in each, so arranged that, when empty, water flows iixto upper tank, which has a perforated bottom and is half filled with animal charcoal. The water filters through this into the lower tank, and if the upper tank fills up by the water not filtering through rapidly enough, the ball tap in it closes and checks the further supply until water filters down ; then the ball drops and opens the tap for a fresh charge, until at WATER SUPPLY. 387 last the lower tank becomes full, when the ball tap in it closes off the supply of water altogether, and the upper tank empties down, drawing air after it through the charcoal, and allowing the charcoal to become aerated and revivified. This filter must be situated in pure air, and the charcoal ?f^R=F^-. ■* If •'