CHAPTER VIII. WATER SUPPLY. (Part 6)

be seen every- where, and these fittings cause great discomfort when they fail Gravity is the cause of the circulation of heated water in pipes. The attraction of gravitation constantly and powerfully draws water and each atom composing its volume down towards the earth. When there are two columns of water in vertical tubes, joined above and below, so as to allow of circulation, they remain in equilibrium if the temperature of each column is alike. But when heat is applied so as to raise the temperature of one column, the I"'" Fio. 861. — Hot- water circulation system defectively arranged. 1. The ex|mnsiou pipe turned over the edge of cistern, as shown, woald discharge hot water in constant flow into the cold cistern. 2. The cold supply to hot cylinder is improiKjrly joined to a cold draw-off, whereby ^ot water would be drawn instead of cold, and the cylinder is in danger of being iptied. 3. Hot draw-oil' in* kitchen is taken from the circulating pii>es, instead of from top jylinder. HOT-WATER SUPPLY. 425 heat causes the particles of water to expand in bulk, and therefore the bulk of water becomes lighter, when heated, than the same bulk in the tube which remains cooL Equi- librium being thus destroyed, the attraction of gravity, which is strongly drawing both columns towards the earth all the time, begins to draw one column with greater force, owing to its relatively greater density over the other, and as the heavy side of a balance, in being drawn downwards, pulls or pushes up the lighter side, so the heavier column of water presses up the lighter column, and will continue to do so, causing circulation so long as heat is communicated more to one column than to the other. Hot water therefore does not rise because it is lighter than cold water, but because the cold water, being heavier, is pulled down by gravitation, and forces the hot water to rise. Comparing two columns of hot and cold air, or two columns of hot and cold water, they are each and all, both hot and cold, seeking to fall towards the earth. Bemove their mechanical supports, and the hot air or hot water will fall by their gravity. They never rise of their own accord from the earth ; they must first be pressed upwards by some corresponding column of greater weight and gravity dis- placing them. Frost is too powerful an enemy to conquer, therefore a plumber's wisdom lies in evading it. All cold-water pipes and cisterns should be well covered and eased, and if pipes are underground outside they should be sunk two feet at least. When pipes are empty, frost has no power to burst them ; therefore, when possible, all exposed cold-water pipes should be emptied in frost, and plumbers should devise the means of emptying them, leaving the responsibility on the householder to use the means at the proper time. A stop-cock and draw-off cock at basement, and a simple 426 DOMESTIC SANITARY DRAINAGE AND PLUMBING. inlet Buction-valve to admit air above at end of each branch, will, when actuated, empty the pipes. A weighted lever to actuate these two taps has been devised, held up by a thin wire attached to a thin glass bottle or tube in a place exposed to frost This lever will fall and empty the pipes automatically in frost by the action of the frost splitting the tube. A new tube is required each time this occurs, but even that costs less than sending for a plumber. Kidd's patent automatic apparatus, now little used, was found useful in Dublin when Vartry water supply was intro- duced. It is most ingenious. A small cistern in scullery or basement, with a draw-oflf tap to empty it, held a double-action ball and cock, through which, when cistern was empty, the water flowed up the rising main to upper cistern. When this upper cistern filled, the overflow or warning pipe was led down to the small cistern, filling which, the ball rose and shut off the upward supply, at same time opening a tap on the rising main, which emptied it. Every can of water drawn from the small cistern by a servant set the apparatus in action again. Frost is systematically guarded against in countries like Canada, where it is always long and severe. Considerable expense is incurred in securing pipes and tanks from its effects; but in this country, where real hard frost comes only once in a way, and then for only a day or two, house- holders will not sanction the cost entailed by precautions against frost, and when it comes hard it finds us unprepared and at its mercy. The plumber suddenly rises in the social scale, and becomes a man of mark to be conciliated and admired at last! We have more frost-bursts in a hard frosty week in London than during a whole winter in frost- bound Canada. UN • • HOT-WATER SUPPLY. 427 Hot-water pipes must be absolutely protected from frost or they become positively dangerous. It will be right to advise that circulating pipes be quite omitted from any house where they cannot be kept under cover and safe from frost ; but where they can be safely laid, they may be made to serve as guards against the action of frost on the cold- water pipes, cisterns, and traps of the house. Bear in mind that the house may be left empty during a week of hard frost, the fires being out, the water cold and frozen ; on the reoccupation of the house, fires may be set going, and an explosion, resulting in loss of life and property, may occur, for which the plumber will be blamed. Familiarity is said to breed contempt, and one must here consider that a long term of immunity from accident has a tendency to induce want of caution. The information acquired in some recent researches concerning this subject of domestic boiler explosions has startled the writer, and has impressed upon him, as he now desires to impress upon plumbers, the urgent need of extreme care and caution in designing and executing even the simplest installations. That domestic boiler explosions are not such uncommon and rare occurrences as we have been led to suppose we shall soon learn. In January, 1881, during a period of 9 days' frost, 32 domestic boiler explosions were recorded in the United Kingdom, and these 32 cases resulted in the deaths of 9 persons and in serious injury to 25 persons. In January, 1894, during a period of 5 days* frost, 22 domestic boiler explosions were recorded, resulting in the deaths of 10 persons and in serious injury to 29. In 1895, between the 3rd and 17 th of February, 44 domestic boiler explosions were recorded, resulting in 9 deaths and 59 personal injuries in a period of one fortnight. Numerous explosions of heating apparatus boilers in 428 DOMESTIC SANITARY DRAINAGE AND PLUMBING. churches, schools, and other buildings also occurred. How many more explosions of domestic boilers took place during these periods, and were for many reasons unrecorded, we shall never know. Our business now is to inquire into the cause of these domestic disasters, and to suggest some methods for adoption for domestic security. Domestic boiler explosions are chiefly caused by frost, and occasionally by incrustations, or by closed stop valves, obstructing the circulation of hot water and sealing up the boiler so that steam accumulates dangerously therein. The usual custom in this country is to fix a boot-shaped or other form of boiler behind the kitchen fire, having a flue constructed underneath and behind, to expose as much as possible of the boiler surface to the full power of the flame ; a strong forced draft is added in all close fire ranges. Inde- pendent boilers may be recommended in dwellings of im- portance, to relieve an overworked kitchen-range from the duty of supplying hot water to the household. Flow and return pipes are usually laid down (on principles — good, bad, or indifterent, as the case may be) between the boiler and a closed tank or cylinder, placed preferably near the boiler in order to shorten the circulating pipes and to facilitate the taking of hot water for the basement from the upper part of cylinder. Sometimes the circulating pipes are led away to a hot- water tank on a high level ; but in either case the cold water is drawn from a tank on a high level The various methods of connecting boilers, pipes, and cisterns need not be discussed here ; it is sufficient to state that the safety of the boiler, and of those persons having a life interest in its condition, depends on the provision of a constant supply of water, and upon the provision of means to keep the circulating, escape, and supply pipes always open and unobstructed. If a boiler, such as here described, be HOT-WATER SUPPLY. 429 hermetically sealed by any obstruction whatever, steam may form in fifteen minutes, and, rapidly accumulating, the pres- sure must quickly reach the point of resistance of the boiler plates, followed by an explosion, the force of which is observed and noted ruefully after the disaster has occurred. No man in his senses would thus hermetically seal up a boiler, yet every year hundreds of boilers are fitted and fixed in such an ignorant and slipshod fashion as to allow king frost to do the sealing more or less effectually. The frost may attack the system in the boiler itself if it is exposed, disused, in an empty house ; the water in the boiler and in any pipes near it may be frozen solid. This probably occurs very rarely indeed, but the possibility of the occurrence renders caution necessary in lighting fires under boilers in cold, frosty weather in newly-inhabited houses. It may be that the only security available in such a case, where fires might be recklessly started, is in the provision of a dead- weight safety-valve of simple and sound construction, placed on the boiler itself in such a manner that if the valve was frozen solid along with the water in the boiler the heat of the fire would melt the ice and free the safety-valve before any damage from excessive steam pressure could arise. In this case it will be noted that a safety-valve on a pipe extended some distance from the boiler, or a safety-valve placed on the circulating pipes or on the cylinder, would be of no avail whatever, as the boiler would explode before the distant valve could be acted upon by the heat. Frost does its work silently, unsuspected, and in a single night — all steam escapes are sealed, fires are lighted in the morning, and explosion follows. A very dangerous point in the hot-water arrangements, and one most frequently neglected, is that portion of the expansion pipe, where it passes through the roof, most exposed to frost. The main cold tank is often placed on the ceiling level 430 DOMESTIC SANITARY DRAINAGE AND PLUMBING. under the roof, and the expansion pipe is sometimes carried along the roof rafters close to slates, or carried up through the roof slates at a point helow the tank level, so that two or three feet of expansion pipe containing water exposed over the slates to frost action is here dangerously liable to become sealed by frost. In such a case, if the cold-supply pipe also becomes frozen, the whole system is hermetically sealed, and explosion follows : or, if the cold supply remains open, the water in the cylinder or pipes is forced back by the steam in the boiler up into the cold tank, thus deluging the house with a flood of overflowing water. Incrustations, also, from hard lime or magnesian waters, or from the action of soft waters, such as the Vartry water, on iron pipes may seal up a boiler hermetically, but these deposits form slowly, and as they close up the bore of the pipes gradually the noise produced by the escaping cooped- up steam and water gives timely notice and creates alarm and inquiry. Serious explosions do not often take place from this causa It is commonly supposed that disastrous explosions sie produced by boilers becoming empty and red hot, and while in this condition receiving a sudden supply of water. This has been proved to be a fallacy. In fact, the cause of boiler explosions has been greatly misunderstood. In 1867 the Manchester Boilers Association made a series of useful experiments to elucidate the subject. Two copper boilers and one cast-iron boiler were heated to redness, when cold water was injected in one case through a ^-inch pipe from the water company's main, and in two other cases through a 1-inch pipe from an overhead tank eight feet high. No explosion followed, and the boilers were unaffected, as the steam blew off through a |4nch escape pipe. In one experiment a safety-valve weighted to 35 lbs, was used, the boiler being of cast iron ; when red hot, cold HOT- WATER SUPPLY. 431 water from a tank with 8-feet head was injected through a 1-inch pipe. The safety-valve did not blow, but the water ia the injection or feed pipe heated back for 15 feet, indicat- ing that a pressure sufl&cient to overcome the small head of water, but quite insufficient to blow off at the safety-valve or to cause an explosion, was generated. The test by pressure- gauge was made to show the actual pressure of steam in the boiler, but all the attempts to explode the boiler by injection of cold water failed, though everything that red-hot boilers and cold water together could do was done and every effort to succeed was made. A very interesting experiment may be made with a copper flask, the neck closed by a cork having a small tube passed through it. Heating the flask to redness and removing it from the fire, a small quantity of water can be introduced through the tube ; the water will assume the spheroidal con- dition noticed by Professor Tyndall, and will be repelled from contact with the red-hot copper, so that steam will not be generated until the temperature of the flask becomes low enough for the water to come in actual contact with the metal, when steam will be generated and the cork blown out. Possibly the pressure, if the flask had been hermetically sealed, would not have sufficed to burst the flask, as the quantity of water from which steam was generated would be so small. This point would be an interesting one to experiment upon further, so as to ascertain the pressure realised. The numerous explanations of boiler explosions include the sudden '' generation of an unknown and highly explosive gas," an explanation most mysterious and alarming, but unsatisfactory, as this gas has never yet been caught in the act, tried, or convicted. The "instantaneous evolution of steam under enormous pressure" following the sudden in- jection of water upon red-hot boiler surfaces affords a more 4:)2 DOMESTIC SANITARY DRAINAGE AND PLUMBING. reasonable explanation of explosion, and is the theory most readily aooepted. Undoubtedly, cisterns and boilers are liable to become empty — whether from frost preventing the supply flowing ; from lack of sufficient pressure in town mains ; from negli- gence of those in charge of pumps ; from cutting off of water supply owing to repairs of mains. This lack of water leaving the boilers liable to become empty, and, therefore, to become red hot, if fires be kept going, would occur, and does occur frequently, except as regards frost, at all seasons of the year ; but we find all the records of burst boilers occur in frosty weather, unless in cases where dangerous stop-cocks on circulating pipes have inadvertently been shut off when fires are lighted, and the boiler thus hermetically sealed when full of water. We also find many cases coming to our notice where boilers give way within a short period owing to lime or other incrustations forming a shell or scale inside the boiler. In these cases the lime prevents contact of water with the surface of the metal plates of boiler. These plates, whenever a specially strong fire is applied, become red hot ; the lime incrustation not expand- ing equally with the metal suddenly cracks, the water rushes in upon the red-hot plate, but no explosion ever follows. The plate cracks, water and a little steam escape, and the boiler sets up a permanent leakage, unless the incrustations re-form over the fracture. Tt may be admitted that very few boilers burst in summer- time. In one or two instances this was found to be due to the shutting off of stop-taps, hermetically sealing the boiler precisely as frost acts in winter. All interesting series of experiments was made and re- corded by Mr. E. D. Monro, chief engineer to the Scottish Boiler Insurance Company, to test effect of a sudden discharge of cold water into red-hot boilers. w HOT-WATER SUPPLY. 433 Being a cautious Scotchman, Mr. Monro placed his boilers and furnace in retired safety within a wrought-iron shell, 20 feet high and 6 feet in diameter; the pipes were all brought outside, where the calm observation demanded by science might be secured, and there the pipes were fitted with steam-gauges, safety-valve, and an indicator tracing on paper the pressure curves. The indicator checked the pressure-gauges, and was found to accord closely with them in action. The water was turned on from a stand-pipe, 2 inches in diameter, 42 feet high, through a stop-valve, and, in some experiments, through a non-return valve, to prevent the return of any steam pressure to the stand-pipe on the admission of water to the red-hot boiler. The boilers used were ordinary commercial kitchen boilers, of representative types. A 14-gallon welded-iron boot boiler, fitted