Water Waste Prevention Survey
First Step, Division of Mains into Permanent Districts—Measurement of District Flow at Frequent Intervals—Surveys for Locating Leaks— Use of Aquaphone—Organization of Properly Balanced Force Essential
FOLLOWING is the conclusion of the paper by Mr. Lanham begun in the January 7 issue, which, as we announced in that number, forms an interesting sequel to the series of articles on a similar subject by William M. Crowe, assistant engineer, Philadelphia Bureau of Water, published in the September, October and November issues, that is dealing with water waste surveys in the city of Philadelphia. The present paper was read by Air. Lanham before the recent convention of the New England Water Works Association at Albany, and created a decided impression at that gathering. This section of the paper deals with water waste surveys in the capitol.-EDITOR.
The lower illustration, (Fig. 4) shows another chart of subdivision night test in residential territory. Note the fluctuation occurring in the rate of flow. Repetition of test and a careful observation are necessary to detect small changes in the flow rate. Note how rate of flow dropped when isolation was opened preparatory to extending it to include Garfield Hospital. The usual method in preparing tor the addition of a square is to close the valve at the far end first, which cuts off the only remaining feed, test the shut-off by opening fire hydrant or other fixtures, and then open the valve at the near end of the square. In cases where the water cannot be cut off as in the case of Garfield Hospital the near valve is opened first, temporarily destroying the isolation, permitting water to flow into the test district through this opening until the valve at the remote end of the square is closed. The recording apparatus for this testing work should produce a chart visible at all times, have a rapid chart movement and be quickly responsive to the smallest changes in rate of flow.
The upper illustration, (Fig. 4) shows a type of pitot recorder used for many years in Washington, D. C. It is known as the Manograph Type A and meets the prescribed conditions.
Fig. 5 shows method of setting up pitot tube and recorder ready for measuring total flow or making tests. The use of indicators without the chart is not satisfactory due to the fluctuating rate of flow always occurring, even in residential sections in the small hours of the morning. The reasons for these fluctuations constitute somewhat of a mystery and they interfere seriously with testing where small flows are involved.
The Use of the Aquaphone
The locating of the night flow first involves the use of all street valves and when the flow is definitely determined as to quantity and location within the closest limits permissible with these valves, recourse is had to the aquaphone or water-phone and the operators listen with it on each curb stop-cock, fire hydrant, lawn sprinkler connection, or anv other fixtures attached to the main within the pre-determined limits. Examinations are also made of all sewer manholes, large sewers, electric or other ducts, and advantage is taken of every facility to determine the exact location of the flow. Flows due to fixtures or other causes within the houses or buildings are readily determined when the aquaphones are placed against the curb stop-cocks and the operators hear the flow passing through the pipe. Closure of the stop-cock, causing stoppage of the sound, proves that the leak or flow is in the particular service pipe under observation or in the building supplied by it and the amount is registered by the pitot recorder, being the reduction in rate of flow coincident with the closure of the stop-cock. Flows due to leaks on the mains or on service pipes between the main and curb stops can be heard on the service pipes, but these flows will not be affected by closure of the stopcocks, nor will any reduction of rate of flow occur at the recorder. The total quantity of flow due to these unaccounted for or so called outside flows,’ may readily be determined by a second test of the entire square with all inside flows shut off at the curb line.
Note the invariable decrease in consumption following surveys as compared to increasing ratesa at all other times.
It is frequently necessary to drive test holes down to the mains and service pipes to permit the use of the aquaphone in definitely locating an underground leak within closer limits than provided by the valves, stop-cocks or other fixtures, increasing loudness at the different points indicating that the operator is nearing the leak. Frequently water or mud will be observed on the end of the steel prod used for this purpose and this indication is utilized. Proper use of the aquaphone is really a science and long experience is necessary for one to become expert in its application to the underground leakage problems. The upper illustration, (Fig. 6) shows a field party actually engaged in prodding for underground leaks, existence of which has been detected by a night subdivision test. The laborer is engaged in driving heavy steel pin through sheet asphalt preparatory to using steel prod and aquaphone. During the progress of the night tests the operator in charge makes notes as to each step in the proceedings and has an instrument tender place an identification mark upon the chart at each point corresponding with the test, signals by lanterns or otherwise being utilized greatly facilitating interpretation of the charts.
This division has located and stopped a total underground waste of over 45,000,000 gallons daily in the past thirteen years.
The difficulties met with in practice are frequently very discouraging, however, and the getting of results in spite of them taxes the ingenuity of the operators. These difficulties consist of inaccurate maps which fail to show important mains, cross connections, valves and other features vital to the proper isolation of the district and individual squares; inaccessible curb stop-cocks which must be cleaned at the expense of much labor, broken valves and stop-cocks; leaking valves, obstructed mains, unrecorded cross connecting service pipes and fluctuating rates of flow, causing confusion and wrong deductions. The lower illustration (Fig. 6) shows samples of underground breaks found only a few feet below the surface their presence having been unsuspected until revealed by the tests.
Fig 7 shows in a most convincing manner the aggregate effect of this work in large sections. Note the heavy decrease in consumption coincident with the surveys as compared to invariable increases at other periods.
The organization of a properly balanced force to efficiently handle the water waste problem is a matter depending considerably upon local condition. In general, the force should be supervised by an experienced engineer with at least one clerk and one draftsman comprising the over head organization and as many field parties as the circumstances demand. Each field party should consist of a chief operator and two or more inspectors, with necessary laboring force to clean out stop-cock boxes, open necessary excavations, operate valves and perform other necessary miscellaneous duties. At least one laborer is required for each inspector and, of course, more will be required if many leaks are found. Fig 8 shows an organization chart, giving the details of a working organization which has saved over 45.000,000 gallons daily underground leakage in the past 13 years. This division is coordinate with the engineering, revenue and other major divisions of the Water Department, Washington, D. C.
Waste prevention surveys have been made in numerous cities along the lines described and the results have been most gratifying. In one city over 45.000,000 gallons daily underground leakage has been stopped in the past 13 years. In another over 2,000,000 gallons daily was the result of only one year’s work by a single field party. Reference to official records of Washington, D. C., Utica, N. Y., Baltimore, Md., New York City, Newark N. J., Havana, Cuba, Perth Amboy, Kearney, N. West Point, N. Y., and many other places reveal data proving the value ofthis work beyond all question. Fig. 3 shows the great reduction in the water consumption of Washington, D. C., accomplished by systematic water surveys during the past 13 years. Many other examples could be cited if space permitted.