CHAPTER VII THE BuILDING—ITs WATER SUPPLY (Part 4)

pipes are kept well away from the face of the wall. THE BUILDING—ITS WATER SUPPLY 225 If placed in any position in which they are likely to come into contact with cold currents of air, as in a corridor, the pipes should be protected against loss of heat by either a spiral winding of strips of hair felt secured at intervals with wire, or by silicate cotton attached to canvas strips and secured by wire in the same way. Cold W.S. Pipe. The cold-water supply pipe to the system can be of iron, copper or lead. Stop-cocks or valves used on the hot- water service should be of the full-way type, to prevent impeding the circulation. Great care is needed in reference to such stop- cocks or valves. They should have loose keys, kept only in the hands of a responsible person, as should a stop-cock be closed and left so, grave danger of explosion may occur. The Expansion Pipe. From the particulars given later as to the arrangement of the pipes, it will be seen that there is a sort of natural safety-valve to a hot-water service in the form of an expansion pipe and also in the form of a cold-water supply tank. Both of these items may, however, unless the system is most carefully arranged, fail by the action of frost, and it is therefore usual to provide a safety-valve of a more definite type. The reason for this is readily seen. If a hot-water service is sealed, the temperature of the water may rise much above 212° F., the temperature at which water boils under atmospheric pressure, and its consequent expansion may be so great that the boiler or the pipes may be ripped open, the issuing water being converted to steam on meeting the air. If there are any stop-cocks on the service, a safety-valye should always be used, in case the system should be bottled up by the unauthorised closing of one. Another possible cause of explosion in hot-water work is the blocking up of the pipes, or any part of them, by the deposit from hard water, but accidents from this cause are unusual, as the reduced efficiency gives ample warning that all is not well. The Safety Valve. The safety-valve can be placed on a short special pipe communicating directly with the boiler, or one of the ordinary pipes, called a return, Just near the boiler; or, best of all, directly on the boiler. There are several kinds of such valve, such as the spring, lever, deadweight, diaphragm and fusible plug. In the case of the spring safety-valve, a cylindrical brass case has a valve at the bottom, and a screw cap at the top with a hole through it. Passing down- wards through this hole is a vertical spindle with an enlarged conical point resting on the valve. Around the spindle, between the enlargement of the conical point and the underside of the screw 8—D.S. 226 THE BUILDING—ITS WATER SUPPLY cap, is a spiral spring, the strength of which can be regulated by screwing in or unscrewing the screw cap. This type of safety- valve is unreliable. As generally constructed, the surfaces in contact between the valve and its seating are too large and liable to become firmly stuck together. The lever safety-valve is a regular item in connection with steam boilers, but it is cumbersome and unsightly in a hot-water service. It consists of a valve held on its seating by a lever having an ad- justable weight at its end. The deadweight safety-valve is the best for a hot-water service. It is simple in construction, compact and efficient. In its usual form, the surfaces in contact are very small. It will be seen from Fig. 191 that the pipe is closed by a ball held down by a casing carrying a number of circular weights. From the smallness of the surface in contact with the ball there is no danger of the valve sticking, whilst even if this did occur, the surfaces would break apart under far less pressure than would be necessary to burst the boiler or pipes. The so-called diaphragm safety-valve is not really a valve at all. Between two short lengths of pipe or tube a sheet of mica, thin copper, or lead is placed, closing the outlet. The thickness of such sheet or diaphragm is proportioned so that it is the weakest spot in the system, and gives way when there is danger of an explo- sion. In the case of the fusible plug safety device, which also is not a valve in the true sense of the word, a plug of fusible alloy is placed in a brass case, the plug being of such a nature that it melts at a temperature slightly above boiling-point, and in this way affords relief to the dangerous pressure that would be existing in the system at such a temperature. All the pipes of a hot-water service should have a fall in order that the system can be emptied, if required, by means of a special draw-off tap provided for the purpose. The methods of arranging the pipes can be best shown in a diagrammatic way, and in studying the following sketches it must be remembered that pipes shown passing from point to point in a straight line do not necessarily follow that course in actual work, it being necessary to determine the routes of all pipes according to the circumstances of each case, such as the fittings to be served and their relative positions, the impossibility of carrying pipes through certain rooms, and so on. The pipes should, wherever possible, be run so as to necessitate only short branch pipes to the fittings. There are three principal methods of arranging the parts of a THE BUILDING—ITS WATER SUPPLY 227 hot-water service, known as the tank, the cylinder, and the com- bined tank and cylinder systems, there being, of course, variations of each. There are many differences of opinion among hot-water system fitters as to the best method of executing certain minor details of the work in any system, but the broad principles of each system are well established. The Tank System. Fig. 192 shows, diagrammatically, the arrangement of the parts of the tank system as ordinarily carried out. The boiler, is fitted with a safety-valve, S.V., and provided with an emptying out pipe, E.O.P., to enable the whole system to be emptied. From the boiler a flow pipe, F, rises to a storage tank, T, near the top of the building, a return pipe, R, completing the circuit of the water between the boiler and tank. Provision must be made for the expansion of the water on being heated, and an expansion pipe. E.P., is provided, leading from the top of the tank. It can be taken through the roof, or, if a cold-supply cistern is near, it can be turned over that, as shown. In either case it should rise at least 1 foot higher than the supply cistern, Its end is open, but if the system is well arranged water rarely issues from it. The cold-water supply is laid on by a pipe, C.W.S., and can be connected to the boiler as shown, or to the tank, or to the top of the return pipe. This is largely a matter of economy and individual preference. The branches to the fittings should be taken from the flow pipe, The dip shown on the cold-water supply pipe, C.W.S., is used to prevent the hot water circulating into such pipe. Direct connection of the cold water to the tank, T, sometimes leads to cold water being drawn from such tank. Hot-water Circulation. The phenomena of water circulation have already been dealt with under the heading of hot-water warming, and it is sufficient to add that they can be easily studied by anyone who is sufficiently mechanical to make a small model of glass pipes and flasks, with the aid of rubber corks and tubing, applying the heat from the flame of a candle. It will be noticed that the flow pipe is taken from the top of the boiler and the return connected to the side low down. _ If this side connection is difficult for some reason, the return pipe may be carried down through the top of the boiler, but it must be pro- longed downwards to give the right direction to the circulation, Fig. 193 shows a section through a boiler with the pipes so con- nected. The flow pipe, F, should be finished flush with the under- side of the top of the boiler to prevent any accumulation of air or steam. Thus, in Fig. 194 the flow pipe is shown wrongly 228 THE BUILDING—ITS WATER SUPPLY connected, with a space between the surface of the water and the underside of top of boiler. The rising water would compress the air and the pressure might be sufficient to do serious damage. Similarly the expansion of the water, on heating, would greatly compress the air, with the same possible result. A further objec- tion is to the noise of the bubbling water when steam forms in this cavity. ; Revert of Flow near Taps. It is important to remember that the conventional circulation of water in a gravity hot-water system is upset when a tap is turned on. The normal force of gravity of water flowing in both directions to reach the tap, over- comes the weaker force of convection. It is therefore desirable to tap only such pipes, and those only in such places, as will give a hot supply. Thus, in Fig. 192 it will be obvious that hotter water will be obtainable from the flow than from the return pipe. Also that hotter water will be obtainable at the highest of the three branches shown, as it is near the storage tank. The boiler is relatively small compared to the tank, and the water would be forced through it fairly quickly if a tap were opened on the lowest branch shown and left open for a while. The Expansion Pipe System. Fig. 195 shows the * Expansion Pipe System” in which all the draw-off taps are taken from the base of the expansion pipe. It has the advantage, in small compact buildings where all the fittings to be supplied are near to this point, that all the hot water ready can be drawn off before any cold water begins to emerge, but it has obvious disadvantages in a larger house, where fittings are scattered over a wide area, as the branch lead has to be emptied of cold or tepid water before hot water from the tank can flow. Long H.W. Branches Without Return. Most water companies and boards object to a hot-water branch without a return, if 20 feet or more long, owing to the consequent waste of water. Fig. 196 shows (on the left) an undesirable method of connecting the cold-water supply as it will mix too freely with the hot water. The method on the right is much to be preferred. Connection to the hot-water tank instead of the boiler will often save plumbing. The Tank System. The disadvantages of the tank system are (1) the water has to travel some distance before reaching the storage tank, so that a good supply is not very quickly obtained; (2) there is a certain amount of heat lost by radiation from the flow and return pipes and from the surfaces of the tank, if, as is often the case, it is put in a roof or cold cistern room; on the other hand, the system has the advantage of (1) relative cheapness compared with THE BUILDING—ITS WATER SUPPLY 229 230 THE BUILDING—ITS WATER SUPPLY other systems, and (2) a good supply of hot water to fittings which are high up in the building. The Cylinder System. The cylinder system, in which the cylin- der is placed relatively low down in the system, ensures a good supply to the lower fittings, but often a poor one to those high up. Hot water is obtained in less time than with the tank system. There is greater safety where water in the cold-supply cistern is liable to run short, it being impossible to empty the cylinder through the draw-off taps, as ordinarily arranged, since they are all above the cylinder. The flow and return pipes are shorter and there is therefore less loss by radiation on the way to the storage cylinder; further, the cylinder is generally put in a warmer position than a tank, usually in the kitchen. On the other hand, the system is rather more costly than the tank system and the cylinder has to stand a higher pressure. Fig. 199 shows an expansion pipe system using a cylinder near the boiler. It is suitable for a house of moderate height provided the fittings are close together, branches being taken from the expansion pipe to them. It will be seen that the hot water will rise in this pipe to approximately the level of the water in the supply cistern—a little higher actually, for hot water weighs less than cold. Fig. 200 shows a more extensive form of the cylinder system, provided with a secondary flow and return taken round past the various fittings so as to supply them by means of short branches. Branches are taken from both flow and return pipes of the second- ary system of circulation, the secondary flow being marked S.F. and secondary return S.R. The position of the connection of the secondary return to the cylinder is of importance. If the house is small, it will be an advantage to make this connection within 4 inches of the top of the cylinder, as shown by dotted line, by which means it will be possible to get a small supply of hot water in circulation around the building in a very short time after the fire is lighted, this water not mixing with the main body of water in the cylinder. In blocks of flats, hotels, ete., where large quantities of water may be wanted at the same time, and where the fire is probably burning slowly all night, the connection may be a foot or so lower, as shown by full line. The letters already used will be adopted in the remaining illustrations to obviate full description in each case. In the remaining examples, also, the safety-valves and cleaning-out pipes are omitted, in order to keep the sketches simple, but they would, of course, be used, as in the cases already dealt with, Fig. 198 shows the method of connecting the C.W.S. THE BUILDING—ITS WATER SUPPLY 231 pipe to the cylinder instead of the boiler, but here, again, as with the tank, it might enter the bottom of the cylinder. To save making two holes through the chimney breast, the flow and return are often brought through the same hole, both entering the side of the cylinder low down, but in such cases the flow pipe must be carried up some distance inside the cylinder. Reflux Values. It is sometimes difficult to find a position for the cylinder in the kitchen or near the boiler; it is then put higher in the building, and branches may be required both above and be- low it. Fig. 201 shows how this can be arranged, the secondary return being joined into the main return. In such case, to prevent relatively cold water being drawn from main return, a reflux, non-return, or back pressure valve is placed at R.V. The con- struction of such a valve is shown in Fig. 197. A light valve of copper is hinged so as to open readily, but also close readily against any attempted back flow of water. An access cap is provided at the top to enable inspection and repair of valve as necessary. A reflux valve of this sort sometimes proves a little noisy. The secondary flow and return pipes are sometimes at opposite sides of the building, and it is necessary to run a pipe from the one to the other, as shown in Fig. 202. In such a case, the slight fall generally available for the pipe is insufficient to ensure a good circulation through this extra pipe, and matters are put right by giving the pipe a “drop” as shown, the greater density of the water at lower part of drop increasing the velocity of flow through the pipe. D.O. is the draw-off. aps oe A method adopted sometimes is shown in Fig. 2038, consisting of the addition of a by-pass pipe, B.P., from the main flow to the secondary. The object of this is to give a quicker hot supply than would otherwise be obtainable, by letting a certain amount of water escape going through the cylinder. Such by-pass must, however, be of considerably smaller section than the other pipes, or the whole of the water will be short circuited and not pass through the cylinder. | Additional power is sometimes given to a hot-water service by using two boilers, say perhaps a back boiler behind a sitting-room grate and the other an independent boiler in the kitchen or scullery, though usually the addition of an independent boiler of sufficient size makes the back boiler superfluous. The method of arranging the connections in such case is quite simple, and is shown in Fig. 204. The flow from the second boiler is joined to that of the first, and the return of the second also joins the return of the first. Each boiler would have its own safety-valve and emptying pipe. THE BUILDING—ITS WATER SUPPLY 232 THE BUILDING—ITS WATER SUPPLY 233 Combined Tank and Cylinder System. The third principal system is the combination of tank and cylinder shown in Fig. 205. It is a system possessing the advantages of both the tank and cylin- der systems and also overcoming the disadvantages of both. The general arrangement will be