The following chapter on "Bath Boilers" is taken from the series of articles entitled "Plumbing Practice," by "Sanitas," that appeared m the fourth and fifth volumes of the Sanitary Engineer.

With the average working plumber there is no feature of his trade of such interest as the fitting up of a hot-water boiler, under the varying conditions of water-supply in the United States and the demands for domestic consumption of hot water, the latter being much greater in this country than elsewhere.

So little is understood of the theory of hot-water circulation by many who essay to arrange the apparatus for it, that we must attribute to that fact the greater portion of the defects complained of by householders generally.

It is not my purpose to dwell on the physics of the subject, as that has been extensively referred to in the pages of the Sanitary Engineer during the past three years, but I shall briefly allude to some of the various means employed abroad to secure hot water for domestic purposes, and compare them with the practice adopted in the leading cities in this country. I am of the opinion that, for our needs and conditions, our best practice is cheaper, more effective, and quite as free from danger as any other that I am acquainted with. Before illustrating the various hot-water apparatus, it may be of interest to some readers of the Sanitary Engineer to have briefly pointed out the cause of the most common sources of complaint and the course to be pursued in dealing with the difficulty.

I shall confine these remarks mainly to the cases of hot-water boilers supplied directly from the street-mains, which is the custom in most cities in this country, and which is liable to more mishaps and casualties than when supplied from tanks, as is the practice in Boston, the reasons for which will appear in the course of these articles.

The principal complaint the householder has to make is that of a rumbling or pounding noise in the boiler. The most common mishaps are the collapsing of a boiler or the bursting of a water-back in the winter time after the range fire has been rebuilt, and when the water in the water-back or connecting-pipes is frozen.

The rumbling or pounding noise, most heard on ironing days, when a hot fire is kept in the range and not much hot water is used, is occasioned by steam being generated in the water-back, which, when it meets with water cold enough to condense it, produces a vacuum. The water coming together again to fill this void space causes the concussion, which makes this noise. The generation of steam is also often due to the fact that the water-back has too much heating-surface for the capacity of the boiler and the domestic requirements for hot water.

To stop this noise and get rid of the steam, it is the custom to open the hot-water faucet. This will accomplish it; but if the hot-water faucet is opened suddenly there is danger of the boiler collapsing if it be a copper one, for the reason that the cold water, suddenly returning to fill the space occupied by the steam, condenses the steam instantly and produces the vacuum, which results in the collapse of the boiler. It is safer to open the hot-water faucet very slowly and thus prevent the sudden condensation of the steam. The risk of collapse is also greater in a city where the water-pressure is very light, as in New York, for the steam meets with so little resistance, by reason of want of pressure, that it more readily forms and more easily forces the water out of the boiler and through the pipes back to the street-main.

The other danger alluded to, and one that this winter has several times been experienced, is the bursting of the water-back, and the consequent demolition of the range. This is solely due to ignorance or carelessness. If a range fire is let down on a cold night, and the water in the water-back or in the connecting-pipes between it and the boiler becomes frozen, so that circulation is impeded, the building of a fire in the range under such circumstances is almost certain to cause an explosion, which might prove fatal to life as well as disastrous to property, for it is manifest that as soon as the water-back becomes heated steam is generated, and if it is confined, and not permitted to circulate, something has to give way, and an explosion is the result. The same thing might occur if both the hot and cold water pipes become frozen. Householders should therefore see to it that during cold weather a fire is kept in the range, so that the freezing up might not occur. If for any reason it is necessary to let the fire out for any period, care should be taken to empty the boiler, to uncouple it from the water-back, and to blow out all the water that may be in the water-back, using a plumber's force-pump for the purpose.

Explosions have been known to occur because so-called plumbers have disconnected the boiler for repairs and forgotten to blow the water out of the water - back, which afterward became frozen, and then, when connecting it again, neglected to ascertain whether the means of circulation were impeded or not.

In considering the various styles of hot-water bath-boilers in use, I will illustrate first a form frequently seen on the Continent of Europe. It is shown in Figure 82.

This consists of a cylinder set over a gas-stove. This reservoir holds about enough hot water for one bath. The cold-water supply from the cistern is connected to it, while another pipe conveys the heated water from it to the faucet over the bathtub. The gas is lit under this reservoir when a person desires to bathe, and in a few minutes the water is sufficiently heated to satisfy the wants of people who have no conception of a more expeditious method.

Figure 83 (which is reproduced from Buchan's " Plumbing ") shows a plan formerly in vogue in Great Britain, which, as will be seen, consists of two tanks communicating with each other. X is the cold-water cistern and W is the hot-water cistern. The water reaches the latter through the pipe Y, on which is a light copper flap, which can be lifted by the pressure of the incoming cold water, but which prevents the return of the hot water. Z is the cold-water pipe to the boiler A, while B is the pipe that takes the heated water from A to the hot cistern W. In the sketch this cistern has a cover, with the pipe H, to permit the escape of steam. When they are not covered the steam is an annoyance in the room in which they are placed, and the tanks soon collect dirt, and require frequent cleaning out. It will be noticed that what is here called a boiler (A) is substantially like what we call a water-back. Of late years the fitting up of hot-water apparatus in England has been gone into more elaborately, and in some respects is carried out essentially the same as it is done in Boston, at least so far as to have tanks or cold-water cisterns to supply their boilers. The latter seems to be a compromise between our water-back and the back-log boilers used in Philadelphia. Figures 84 and 84A show two forms of boilers. The latter is termed a "saddle-boiler," and is made the shape of the arch of a stove front, and is fixed in the stove as shown in Figure 85. The dome-top bath-boiler shown in Figure 84 is set in brick-work, as shown in Figure 86. It will be seen that this requires a separate fire, which with us is avoided, as the ordinary kitchen-range performs the duty of heating a limited amount of water for domestic purposes, in addition to its other functions.