Taps. The taps and other fittings allowed by various water companies vary according to the idiosyncrasies of their officials; hence we often find that those which are permissible and even recommended in some districts are prohibited in others.
Picture 62 shows an ordinary screw-down valve which performs the functions of a stopcock, so as to shut off and regulate the supply.
Picture 62. Stopcock.
Picture 63 shows a section of one of Lord Kelvin's patent bib-taps, which are made in no less than twenty-six different sizes.
Picture 63. Kelvin's Tap.
Picture 64 shows a quarter-turn bib-valve, which should only be used on a low-pressure system, or the pressure of water would tend to open the valve, while shutting it off suddenly might burst the pipe.
Picture 64. Quarter Turn Bib Valve.
Picture 65 represents the section of a clear-way wheel-valve, which is useful in connecting fittings where the pressure is low, and it is desirable that when open the valve should not materially check the force of the supply.
Picture 65. Clear Way Wheel Valve.
Picture 66 is a section of a quick-turn full-way valve, the full-way being obtained by the extra sectional area of the body of the tap.
Picture 66, Full-way Valve.
Picture. 67 shows a spring valve, which is sometimes used for lavatory basins, where the supply of water is limited and it is desired that no waste shall take place.
Picture 67. Spring Valve.
Picture 68 shows a bath fitting with a mixing box and thermometer, an arrangement which is useful for obtaining water at any required heat.
Picture 68. Bath Fitting.
Picture 69 represents an ordinary flap-valve, which is mostly used for the ends of overflow pipes to prevent the ingress of birds, dirt, etc., and is also useful in preventing cold weather affecting the ball-valve.
Picture 69. Flap-Valve.
Picture 70 represents a full-way ball-valve, which is to be recommended owing to its simplicity and to the fact that it acts directly and a full supply is obtained.
Picture 70. Full Way Ball Valve.
This type is particularly suitable in cases where only a low pressure is obtainable. A pipe should be carried from the inlet to the bottom of the cistern so as to reduce the noise of the inrush of water.
Whenever a Fuller bib-tap or a spring self-closing tap is used, they should always be provided with an air chamber, otherwise their sudden closing gives rise to the loud knocking sound which is technically known as water hammer. The explanation of this is that when water issues from a tap the whole body in the pipe is in motion. When a screw-down tap is closed the motion of the water is gradually arrested. In the spring self-closing types the sudden arrest of the motion causes the jarring in the pipe unless air chambers are fixed, but when this is done the air in the chamber is compressed and acts as a buffer.
Picture 71 shows an air chamber when the tap is on an ascending pipe, and picture 72 when the tap is on a rising main or on a pipe which also supplies an upper fitting.
Picture 71. Air Chamber.
Picture 72. Air Chamber.