In many sections of the country, owing to the nature of the soil through which the water supply flows, water supplied for domestic purposes is exceedingly hard, and therefore naturally presents a most difficult problem for the community to solve. It does not concern the supply for drinking purposes, for the flushing of water closets, and for certain other uses, but hard water is entirely unsatisfactory for toilet use, for washing clothes, the washing of dishes, etc. Furthermore, while hot water that is hard would be objectionable for many uses, the heating of hard water is also attended by a very great annoyance in the rapid filling of the water front and range connections with a deposit of lime, making their frequent renewal a matter of much expense and inconvenience.
Under these conditions, a system of hot and cold water supply known as the three-pipe system, may be used to very great advantage. The general features of this system may be observed in Plate 56.
Plate LVI. The Three-Pipe System Of Supply
Plate 56. Three - Pipe
System of Supp/y
In the installation of the three-pipe system, three lines of supply are provided to such fixtures as sinks, lavatories and wash trays, where hard cold water may be required for drinking or rinsing purposes. From the three bibbs at these fixtures may be drawn soft cold water, hard cold water, and soft hot water. At baths hot and cold soft water may be drawn, and of course water closets are provided with hard cold water only.
It will be understood that in places where the natural supply is hard, any supply of soft water that may be obtained must be used as economically as possible.
The system is simple in construction, and not expensive to install, although costing somewhat more than the common system. The street supply is piped direct to the pump, and from the pump direct to the fixtures which are to be provided with hard water. When hard water is drawn at any of these fixtures, the street supply passes through the pump, serving also to operate the pump, thereby causing the latter to draw soft water from the cistern and deliver it to the attic tank.
From the soft-water tank in the attic, a supply of soft water is piped down to those fixtures requiring this kind of water, and a branch taken to supply the range boiler. Thus nothing but soft water passes through the boiler, water front and connections. From the boiler, hot water is delivered to fixtures in the ordinary manner.
It is necessary to provide for a supply of hot hard water, in the event that the supply of cistern water fails. This is done by means of the connections and valves at the pump. When there is a supply of soft water available, valves A and B are closed, and valve C open. When the soft-water supply gives out, and hard water must of necessity be used for all purposes, all that is required is to open valve B, which will allow city water to fill the entire system, including the boiler.
When the cistern is empty, and it is required to use only hard cold water, valve B should remain closed, also valve C, and valve A opened. This will allow city water to enter the cold-water piping, without passing through the pump.
The attic tank should have an overflow pipe, and if economy in the use of soft cistern water is to be observed, the pipe should lead back to the cistern, in order that the overflow water may not be lost. Instead of running as shown in our illustration, the overflow may discharge onto the roof, and from this point flow back to the cistern.
If a supply for sprinkling or other such purpose is to be provided, connection should be made on the street side of the connection to the pump, as at X, so that sprinkling may not keep the pump operating.