Before proceeding further with the piping inside the house, there is the hydrant to be considered, which is shown in Fig. 252. The hydrant cock or shut-off is of special design as shown, and should be of the waste pattern, in order that all water in the vertical pipe may drain into the ground when the cock is closed.

Fig. 252. - Hydrant Connections.

A rod carried to the surface is operated to open and close the hydrant cock.

On high-grade work, it is often customary to lead the main supply pipe directly to a keyboard. Such work is shown in Fig. 253. The main line of supply is run directly to the keyboard, from which every cold-water supply pipe in the house is taken. Each line is provided with a stop- and wastecock, and the waste from each cock connected into a main waste which should be carried to some open fixture into which it may drain. Laundry tubs, which are often located in the basement or cellar, are sometimes used for this purpose. The ends of the header should be provided with tees rather than elbows, in order that any future line may be easily taken off. The end tees should be plugged.

When lead supply pipe is used, the keyboard may be made a very neat thing, as much skill may be put into its construction. The keyboard shown is designed for the cold-water supply. An additional keyboard may be used for the hot-water supplies, and a third one for the circulation or return pipes. On very nice work, polished brass supply pipe is used to a large extent. When brass is used, a very neat system can be obtained by the use of keyboards and by bending the pipe instead of using elbows and offsets. When a header is used for the hot-water pipes, the hot-water pipe from the boiler is carried direct to the keyboard, and from that point delivered to the several lines. When a circulation or return header is used, it should be connected into the return opening of the range or heater. In order to derive full benefit from the use of the keyboard, each valve should be tagged with the fixtures and room that it supplies. Very neat nickel-plated tags, with the proper words stamped on them, are now made for this special purpose.

Fig. 253. - Keyboard.

Fig. 254. - Attic Tank and Connections.

Keyboards make the work very systematic, and rob the supply of much of its mystery to the inmates. Whenever any defect or trouble with the piping arises, they may go at once to the keyboard and shut off the proper valve, avoiding the loss of time in hunting for the proper valve which is necessary in ordinary work. The loss of this time in the event of a serious break, often means great damage to the property from escaping water. Keyboard work is necessarily somewhat more expensive than ordinary work, but its value should commend it to much greater use than it has. If the keyboard is not used and the tank system of supply is used, the supply should be run to the attic tank, which with its connections is shown in Fig. 254.

There are two systems of supply in common use, the pressure system and the tank system. In the pressure system, the range boiler and all fixtures are supplied with water under street pressure. In the tank system, a tank is located in the attic, above all fixtures, this tank being supplied from the house main through a ball cock.

, Years ago the attic tank was of large size, and used as a storage for water, often holding several hundred gallons. From this tank the entire supply for the house was delivered, including the range boiler and all fixtures.

In the use of the present tank, however, it is designed chiefly to supply the range boiler, the cold-water supply to fixtures being under street pressure. In the tank system as at present used, then, the hot-water supply is under tank pressure, while the cold-water supply, with the exception of the boiler, is under street pressure. As water is drawn from the hot-water piping at any fixture, an equal amount enters the attic tank through the ball cock, thus keeping a uniform supply of water in the tank.

There are certain advantages to be gained by the use of the tank system. In the first place, the pressure of water in the tank system is always uniform, whereas the street pressure varies greatly from many causes, such as a greater use of water at certain times of the day than at others. The pressure of the tank system being always uniform, the wear and tear on piping and valves is at a lower rate than in the use of the pressure system.

Lighter boilers may be used on the tank system also. The attic tank as now used is of far smaller capacity than the old-style attic storage tank. It is usually of about 50 to 60 gallons' capacity, lined with copper, and set up from the floor on pieces of joist. A very convenient size of tank is 2 feet in length, by 16 inches wide, by 15 inches deep. This is a small-sized tank, but cuts the copper to advantage.

The tank is generally supplied through a top supply ball cock. The supply to the boiler is taken from the bottom of the tank and should be provided with a stopcock close to the tank, as shown, in order that the supply to the boiler may be shut off from this point. In the case of several apartments, a single attic tank of larger size, may be used, with separate supplies taken out for the different apartments. An overflow should be run to some open fixture. It is often convenient to run this pipe into the flush tank of the water-closet in the bath room on the floor below. In the use of the pressure system no special provision need be made for expansion, as the expansion due to the hot water will be through the piping into the street main, and thence back to the reservoir. In the tank system, however, special means must be provided to take care of the expansion.