130. Flow Pipe.
There are a number of errors commonly found in apparatus that has been fitted up by those somewhat wanting in experience, such as connecting draw-offs from the return pipe in No. 2 system; result is that the whole of the water in the tank having to be heated before any hot water finds its way down the return pipe, it is naturally a considerable time after the fire is lighted before hot water can be obtained from the tap; connecting draw-offs direct from the tank, result nearly as bad as connecting from the return; dipping or trapping the flow pipe, causing circulation to become air-locked as before mentioned; connecting the cold supply to the tank or cylinder without forming a syphon (inverted) in the pipe, so permitting hot water to find its way up into the cold-water cistern: result, loss of heat and water lukewarm which should be cold; placing tank and pipes in very cold situations, causing serious loss of heat, as before explained. Another common error, or piece of bad work, is connecting or screwing the flow pipe through the top of the boiler so that it projects through the inner surface, as Fig. 130. Now when the apparatus is finished it is, of course, before being charged with water, full of air; when the water flows in, it expels the air as it fills, but it cannot expel the stratum of air existing between the lower edge of the flow pipe and the top of the boiler; this is not noticeable when the water is cold, but when heat is applied and steam is generated, the steam naturally wants to expand into this space, but at the same time the air has no desire to be evicted, so a struggle ensues, and the steam is eventually the victor; but the struggle is fierce, and can be heard and felt in every part of a building of moderate size. The trouble does not end here, for when the position is gained, the steam has to pass away, when it has gained sufficient strength to force its way back through the water and up the flow pipe, and this is an unpleasant experience. Exactly the same result is obtained if the rising main is screwed too far through the top of cylinder or the expansion too far through the top of tank—an air or steam chamber is formed in either case; these pipes should be quite flush with or above the inner surface of the receptacles they are screwed into. There is no more annoying or alarm-producing error than this.
Still another error is in running the circulating pipes up a casing containing other pipes without felting the former, or even without separating them; the result of placing a hot pipe against a cold one for several feet is obvious, and if a hot pipe is placed against a soil (w.c.) pipe, the result is offensive; these errors are commonly found. There are numberless minor errors to be met with; to enumerate all would occupy much space and be of no real use to the reader. Errors are not uncommon things in this work, and some of them are of so extraordinary a nature as scarcely to be creditable. An objectionable feature in an old apparatus is the small supply or feed cistern fixed at the side of the tank, but this is now almost totally in disuse, for it has at last dawned upon some one that it is quite unnecessary; this feed cistern must have a ball valve or cock, and, this is where the mischief lies, no reliance can be placed on a ball valve or cock of any description; they are commonly a source of never-ending trouble. We give this description, as there are some people who still persist in the use of this secondary cistern.
Discoloured water is sometimes caused by the rust that is naturally created in new work, and lasts but a short time, as the pipes get covered internally with a very thin coating of lime, which then prevents the water coming in contact with the metal of the pipe.
Water is discoloured to a greater or less extent if it is permitted to boil very hard, as this agitates any loose sediment that is lying in the tank, and the boiling is much like churning the water.
The water in the tank or cylinder should not be permitted to boil, as it creates an unpleasant noise, and is a certain strain upon the work, and answers no good purpose; it can be stopped by drawing a quantity of water off, so causing cold to flow in, but the remedy is to keep the boiler flue closed by the damper; if this does not prevent the overheating of the water, there is the possibility that the flue is out of order, or “leaks.” This can be tested by closing all the dampers when fire is in working order, which in the ordinary way would cause all the smoke to be discharged into the room; if this is not the cause, there must be an improper exit for the smoke and heat, and a loss is of course being sustained.
Coils and hot-water pipes for heating a small conservatory or chamber are sometimes connected with the circulating service, or direct by a distinct service from the boiler, but there are no especial rules to be observed in using these, as there are only stop-cocks to be turned on or off as the requirements demand.
It may now be useful to give a few hints to those having a new apparatus fitted.
There is a rather old saying to the effect that the “best is the cheapest”: this especially applies to hot-water work. It would be waste of time and space to enumerate the evils of cheap work of this description, as the list would be a very long one. The best plan is to apply to a good firm (not necessarily a large one) who makes somewhat a specialty of this branch (generally boiler or stove manufacturers, or good plumbers and builders). They will provide an estimate of cost with detailed specification free of charge if the distance is not great. The object of a detailed specification is, as probably the reader guesses, to know exactly what size, strength, quality, &c., of boiler, cylinder, or tank; pipes, iron and lead; cocks, &c., &c., that are to be used; and before finally deciding, the purchaser should insist upon the efficiency of the apparatus being guaranteed. Boilers are of many various shapes and sizes, but the best form has been proved to be that with a good flue or heating surface underneath, so as to present as much bottom or under surface as possible to the flame and heat; the best surface is easily determined by any one, by applying the heat to the top of a kettle, and afterwards applying it at the bottom, and noting the difference in results; there are many other perhaps better forms of boilers made for heating purposes; but it must be remembered that the boiler for hot-water supply must not be of complicated form inside, but must be quite clear, offering every facility for removing the incrusted deposit. Fig. 131 shows the common form of boiler used in kitchen ranges; the size must be governed by the capacity of the range itself, but it should have as great a width and length as possible, to increase the bottom surface; and the flue should be as large as the size of fire will possibly permit. A most important point is to see that the boiler has a large manhole easily accessible.
