CHAPTER VIII. WATER SUPPLY. (Part 1)

CHAPTER VIII. WATER SUPPLY. Water, named by chemists protoxide of hydrogen (its sym- bol, OH2 ; its equivalent number, 18), is known to plumbers practically in three distinct physical conditions: as solid, in ice, when it suddenly expands with resistless force before it reaches 32" F., or zero C, and bursts the pipes and cisterns containing it; as liquid, in water, whether clear, transparent, colourless, and pure, for drinking and domestic uses, or acting as the carrier of the sewage from dwellings ; as gaseous, in steam, when it passes 212** F., or 100** C, expanding enormously in bulk, and, when guided and re- strained, doing a vast amount of work for the benefit of mankind. Water consists of two volumes of hydrogen and one volume of oxygen gas, or, by weight, 1111 per cent, of hydrogen and 88'88 per cent, of oxygen, oxygen gas being sixteen times heavier than hydrogen. In water these two gases are chemically combined; they lose their properties as gases and become a new substance. Water has such great power of dissolving substances and absorbing them, that it is never met with in nature absolutely pure. It is diflScult to render water by any means absolutely pure. Even if water pure enough for domestic use is ob- tained, it is not easy to preserve it in a pure state, owing to its tendency to absorb all impurities in cont«tct with it. 867 368 DOMESTIC SANITARY DRAINAGE AND PLUMBING. The source of all water supply may fairly be traced back to the ocean and the clouda A rough average of thirty inches deep of rain falls annually in England. Quantity of Rain-watbr flowing from Roofs ok Surfaces for ivbrt Thousand Suprrficial Fskt. Rainfall per hour . . . 1 inch. i inch. i inch. i inch. Gallons per minute . . 9 4^ 2^ 1^ Rainfall per twenty-four hours 1 inch. i inch. J inch. | inch. Gallons per hour . . 22 11 5^ 8 The greatest extraordinary rainfall within a certain limited number of minutes has been found, after careful observation, as follows : — Timeof Pkll. POMible ADoont. luehes. Rate per Hour. Inehet. 1 minute ... -2 .... 12 5 minutes 76 9 J hour . 1 4 1 M . 1-8 8-6 1 n . 8-26 8-25 2 hours . 86 1-8 8 „ . 4 1-88 We see by this table that suddeb rain-storms of short duration may discharge enormous volumes of water in a few minutes, complicating the question of storage, and rendering the collection^ of the entire rainfall very difficult in country mansions. The consumption of water goes on continuously, rather increasing in dry weather, when supply falls short. A month or two may occur when no rain falls, and then a storm of a few hours or minutes may fill all tanks to over- flow and waste. In making arrangements for the water supply of country houses, dependent solely on the direct rainfall, plumbers must ascertain the actual rainfall of the district for a series of years, because the average of 30 inches lies between the WATER SUPPLY. 369 distant extremes of 65 inches in Cumberland and 25 inches in London, in some districts as low as 15 inches in dry years. The actual rainfall may be ascertained in any district by means of rain-gauges. These are made in various forms, the simplest being a metal cylinder with a glass tube rising outside from the bottom, divided into inches. The cylinder is covered by a funnel, to prevent evaporation. The depth of the rainfall is read off direct from the water level shown in the glass tube. An objection to this form arises, namely, that the glass tube may burst in frosty weather. A float, with a graduated scale attached, rising with the water level, is sometimes used in preference. The gauge adopted by Mr. Symons, the well-known meteorologist, consists of a cylinder, which receives the rain, and a small glass vessel with a graduated scale, in which the amount of rain collected is accurately indi- cated. Costly self-registering rain-gauges are also constructed, and are used in all well-appointed observatories. The plumber should be acquainted with the forms of these instruments, in the event of his practice extending to the colonies or foreign lands ; but in prsu^tice in England they will not be required, as he will find accurate tables of rain- fall published by Mr. Symons. The results of extended observations in any part of the United Kingdom may be obtained at a very small cost, thanks to the efforts of that persevering meteorologist. One inch of rainfall yields 22,622 gallons per acre; 32 inches, therefore, yields 723,904 gallons per acre. Something near one-half of this quantity is lost by evaporation ; the other half sinks into the soil, and becomes available for the supply of wells, streams, and reservoirs, 370 IX)MESTIC SANITARY DRAINAGE AND PLUMBING. liainfall upon slated roofs may be rapidly stored, so that loss from evaporation shall be at a minimum. The plumber will have to consider rainfall mainly in con- nection with house supply ; he will ascertain the amount of roof surface available for collecting the rain, any hard clean surfaces of yards and areas may also be ultilised to fill imder- ground tanks for such purposes as the washing of carriages, laundry work, etc. ; but this water would not be safe to use for drinking or cooking, nor should any risks be allowed of such water getting at any time mixed with the general water supply of the dwelling. In supplying a house exclusively with rain-water, every available gallon should be safely stored, but this arrangement involves very large storage tanks. Assuming the fall to be thirty-six inches, and supposing the fall to occur regularly of three inches per month, then a moderate-sized reservoir would suflBce. Practically, this regular fall never takes place ; the fall will be found to be irregular, one month yielding no water, another month yielding six inches, and perhaps so much as three or four inches falling in two or three days. In order, therefore, to secure all this rainfall, the storage space must be large enough to retain all the storm water, for if any be lost through overflow, it cannot be recovered. Assuming the area of the roofs of an ordinary country house with its out-ofiicos to be two thousand square feet, available for the collection of the rainfall, measuring the flat plan of the house from out to out of the eavee (not the more extended area offered by the slope of the roofs), we may rouglily find the number of gallons by multiplying the area in square feet by half of the rainfall in inches. The product gives in this instance 2,000 x 18 = 36,000 gallons a year, supposing that every gallon is secured, and not WATER SUPPLY. 371 making any allowance for loss, evaporation, storm overflow of storage tanks, etc. It will not be safe to calculate on storing more than half this amount for use = say 18,000 gallons. For this purpose the storage tank should measure 18 feet X 8 feet x 5 feet deep = 4,500 gallons, or for one- fourth of the total annual amount calculated. If such . extensive storage can be provided, there is no doubt that the rain-water caught by the roofs and yard surfaces of an ordinary country house may be collected in sufficient quantity for an efficient and economically restricted supply for all domestic purposes throughout the year, while it will be also desirable to supplement the supply from other sources in the event of an unusually dry year. Devices for separating impure from pure roof waters are ingenious, but liable to go out of order from frost and neglect ; they send a quantity of the water away to waste, they have been much admired as ingenious contrivances, but they require too much attention to be of practical value. Plumbers should examine these and all such novel con- trivances, and test them at work, considering carefully the purposes they are intended to fulfil, and also the difficulties and special obstacles, such as frost, floods, dirt, corrosion, wear and tear, exposure to sun, rain, heat, or cold ; endea- vouring to picture to his mind these points, and how far the apparatus or appliance in question is likely to meet them, not alone when first fixed, but in five or ten years after. Eain-water approaches nearest to purity after a con- tinuance of wet weather, yet it always contains atmospheric air, and such gases as may be present in the air. After a spell of dry weather the first rain-water from roof surfaces contains traces of nitrates, nitrites, ammonic salts, often of common salt and other impurities; but the chief dangers 372 DOMESTIC SANITARY DRAINAGE AND PLUMBING. of rain-water impurity arise from the defective arrangements for storage adopted, where the overflows of tanks communi- cate with foul drains and cesspools, where organic impurities are not rigidly excluded, and where means for periodic cleansing of the storage tanks are not provided. Spring waters always contain saline matters dissolved, the nature of the salts depending on the strata of the ground in which the spring appears. In these waters calcic carbonates and sulphates are the usual impurities, also magnesio carbonates and sulphates, and common salt. New red sandstone waters contain sulphate, and so does the water of shallow wells, mixed with other impurities. In London gravel nitrates and ammonic salts from sewage contamination are often found in shallow-well water. The contamination of shallow wells varies so much at different times, that an analysis taken at any one time does not afford a reliable test of the average quality. With deep wells the contrary result obtains, and analytic tests are fairly reliable. Such waters are generally good and pure. Most spring waters contain carbonic acid, which dissolves much calcic carbonate. There is no actual proof of injury to health caused by this lime impurity in waters. Eiver waters in this thickly-populated country are unfit for drinking, or even for cooking purposes, being invariably more or less polluted with sewage. The smallest amount of sewage renders such waters unsafe, and at certain times extremely dangerous. One typhoid-fever patient on the banks of a river might so foul the stream that the disease would be communicated to thousands of healthy persons. Waters are known as hard or soft, according to their action on soap. Calcium and magnesium compounds in hard WATER SUPPLY. 373 water cause it to curdle soap; while soft water, on the contrary, dissolves soap freely* It has been stated authori- tatively that the substitution of the Loch Katrine water, of one and a half degree hardness, for the water of eight degrees hardness formerly supplied to Glasgow, caused a saving to the inhabitants of that city of 2s, per head, or about £36,000 per annum in the item of the washing soap alone. The hardness of water is measured in degrees. One degree of hardness signifies that one gallon of the water contains one grain of carbonate of lime or chalk; if the hardness be due to other salts, it is reckoned as being equal to a proportionate amount of chalk. Thus, water of six degrees of hardness means that it would waste as much soap as six grains of chalk dissolved in the water would waste. Every grain of chalk, or, in other words, every degree of hardness, destroys or curdles eight grains of soap before a lather can be produced; these eight grains are therefore wasted, and this provides a measure whereby we may esti- mate and define the extent of hardness in any water. Some kinds of hard water are capable of being rendered soft by boiling. These are termed waters of temporary or removable hardness; while other kinds, incapable of alteration by boiling, are termed permanently hard waters. Permanent hardness is produced by calcic and magnesic sulphates, etc., which cannot be eliminated by boiling. Temporary hardness is produced by calcic and magnesic carbonates^ which salts are freely soluble in waters containing carbonic acid. When the process of hard boiling for some time expels this carbonic acid, the water can no longer con- tain the calcic and magnesic carbonates in solution. They are, therefore, then precipitated as a powder, and they form a strongly adhesive fur or incrustation on the boiler, which often causes trouble to the plumber. If calcic sulphate be in the water, a portion of it is also deposited. 374 DOMESTIC SANITARY DRAINAGE AND PLUMBING. The carbonic acid in the water, which holds these salts in solution, can also be removed by the addition of a certain small proportion of lime water, which absorbs the carbonic acid, so that both the lime dissolved in the water and that in the added lime water are precipitated together as calcic carbonate. This softening process, known as Dr. Clarke's, is of great value, and is successfully applied on large and small scales to waters containing much calcic carbonate or carbonate of lime in solution ; but it is only applicable to waters of temporary hardness. This deposit of lime in boilers is a very serious matter. As it increases in thickness, the iron plates of the boiler become separated from water contact, causing the water to heat more slowly, till at last a stronger fire than usual must be applied. The iron plates become red hot, expanding so as to crack the layer of rigid lime incrustation; a split occurs in the lime, and water rushes in on the red-hot plate, suddenly cooling the outer edges of the red-hot area, which edges, in contracting, force outward the softened hotter central portion of the area, and forming the blister we so frequently see on boilers where a leakage has occurred. Probably there is also a sudden force or pressure generated at the moment of contact of water with the red-hot plate, which crjtcks the iron plate across the blister outward. Water must be boiled for a considerable time, and the ebullition must be very strong, in order to expel the carbonic acid gas in sufficient quantity to reduce the hardness natur- ally by causing a large deposit of lime. Plumbers may, therefore, learn the useful lesson that, when compelled to supply very hard water to kitchen and bath boilers, they should so plan their system, either by reducing the power of the fire on the boiler, or by using extra large hot-water circulating cisterns, that the water WATER SUPPLY. 375 should never reach boiling-point. By this means the deposit of lime may be materially reduced. It is only when boilers toil and bubble that the hard incrustation deposits rapidly ; such waters are almost useless, therefore, in steam boilers. Special care must also be taken in these cases to provide ready and ample means for cleaning the interior of boilers and pipes. A defined period for cleaning them should be fixed on, according to the hardness of the water. Every boiler should be opened and cleaned at least once every year; some need this operation every quarter, if incrusta- tion forms rapidly. The report of the Eiver Pollution Commissioners classifies several waters in this order as regards their hardness: 1. Eain-water (softest). 2. Upland surface water. 3. Sur- face water from cultivated land. 4. Polluted river water. 5. Spring water. 6. Deep-well water. 7. Shallow-well water (hardest). They consider waters soft which are under six degrees of hardness. They classify several waters in this order as regards quality: 1. Spring waters. 2. Deep-well waters. 3. Upland surface waters = wholesome. 4. Stored raiii waters. 5. Surface waters from cultivated land = suspicious. 6. Polluted river waters. 7. Shallow-well waters = dan- gerous. They consider spring and deep-well waters the best and of inestimable value, and worthy of great efforts to secure and preserve for use. Plumbers should treasure in their minds these results of scientific inquiry and laborious research, and be in a position to give reliable advice when their advice is asked for. Testing water for impurities does not come within the plumber's sphere, nor is it to be desired that so important 376 DOMESTIC SANITARY DRAINAGE AND PLOMBING. a question as the quality of a water for household purposes should be settled by any but a skilled analytical chemist Simple tests, which can be used in a preliminary fashion to detect suspicious appearances in water, may sometimes prove serviceable, such as simple tests for lead, zinc, iron, copper, and even sewage impurities. The simple preliminary tests which may be taken to cause or establish suspicions of certain impurities in waters should not be considered as finally determining water quality for domestic purposes. For sewage impurities in water — Take permanganate of potash or Condy's fluid, which communicates a bright violet-rose colour to the water when added. Take a glass of the water, and add four drops of permanganate, allowing it to stand two hours. The rose colour will change to dull yellow if decomposed organic matter be present in dangerous amount. The rose colour will in time disappear completely if there be a very large quantity of dangerous matter present. The rose colour will turn paler, but retain a decided red tinge, when some, but not an immediately dangerous, amount of organic impurity is present. If the changes indicating impurity occur sooner than in two hours, the quicker and more decided the discoloration the greater the quantity of decomposing organic matter present. For lead impurity (acetate of lead) — Take sulphide of ammonium, and add six drops to a small glass of water. The water will turn black if lead be largely present, but it will also turn black if other metals, such as iron, mercury, silver, etc., be present ; so to localise lead a second test is desirable. WATER SUPPLY. 377 Take chromate of potaseium, and add four drops to a email glass of the