WA STE-WATER METERS OR DISTRICT METERS indicate the rate of consumption per unit of time, instead of the aggregate volume. A hori zontal disk is so placed in a chamber shaped like the frustum of a cone as to he lifted by the flow of water upward through the chamber. The greater the volume of water passing through the pipe in which the disk is set, the higher the disk will lie lifted, in order to increase the annular space through which the water must pass. The disk is connected by means of a wire with a counter-weight and pencil. When the disk rises the weight and pencil fall. The pencil makes a mark on a paper placed on a drum revolved by clockwork. The paper is ruled vertically for elements of time and horizontally for units of volume; thus the device registers the rate of flow. Such meters are so located that all the Nvnter of a district must pass through them. By comparing day and night rates of eonsump thin of various districts, abnormal conditions may be detected and further steps may be taken to ascertain the cause of the waste. See WATER WoRKs.
The meter just described was invented by Oeorge F. Deacon. of Liverpool, England, and has been more widely used abroad than in Amer lea. The Venturi meter may be employed for the same general purpose. It was invented by Clemens Herschel, of New York City. about ISS0, but the fact that there is a relation between loss of pressure in a contraeted tube and the amount of water flowing through it was discovered by Venturi in 171)G. One of the earliest water meters in the United States was the double piston meter, invented by Henry It. Worthing ton, who also introdueed the direet-acting steam pump. Numerous other American meters have been developed to a high state of effiCiency. For sizes from to 4 inches in diameter almost any of the well-known makes of positive or in ferential meters may be used. Some manufac turers, however, advise a number of 2-inch meters in place of one of a larger size. Some of the
highest grade of piston meters are made in sizes of 0 inches or even higher, and an inferential meter of the screw type has been made up to 30 inches in diameter. Venturi meters from 2 inches to GO inches in diameter were in use in 900, and some P4 inches in diameter were then being made. A meter 10S inches in diam eter was built some years ago for experimental purposes. There is practically no limit to the possible size of Venturi meters. but for diameters of G inches or less the meters with moving parts are cheaper. One of the points of superiority claimed for this meter is that it causes less loss of head, or reduction in pressure, than any other type. The durability and simplicity of the Venturi meter is another point in its favor.
The working parts of meters are made as light and durable as is consistent with accuracy and serviceability, and they are generally so de signed to be supported by the water, thus reduc ing wear and tear and loss of head. Vulcanized rubber is the most comMon material for the disk and some of the rotary piston meters, but where special strength or power to resist the action of hot water or acids is required. brass or some other composition metal is employed. A variety of devices to protect from damage or clogging are used, including strainers and sieves to keep out gravel and fish, frost cases, and the like. For most purposes a high degree of accuracy of measurements is not an essential quality in a meter. but it is desirable that meters should he sutheiently sensitive to small flows to detect leakage, which, though minute. may amount to large quantities in the course of time. Positive piston Meters come to a standstill whenever any thing prevents their registration. The inferential and some of the disk meters cease registering without any effect upon the flow of water.