Water Waste Prevention Survey

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.

Fig. 66—Upper—Field Party of Water Survey Division of Washington Water Department Preparing to Prod for Underground Leak Not Showing on Surface.Examples of Leaking Service Pipes. 1. Corroded black Iron pipe, about twenty-five years old. 2 and 3. Defective piped joint due to poor workmanship a frequent cause of waste. 4 and 5. Dead pipes damaged by freezing. 6. Broken iron pipe. Breaks are more frequently found at elbows and toes than elsewhere. 7. Corroded iron pipe. 8. Defective stop-cock caused by to withstand rough treatment caused by difficulty in placing keys.

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.

Fig. 4—Upper—Type A Manograph. Special Type of Pitot Recorder Used in Washington, D. C., for Subdivision Tests.Night Subdivision Test Chart Taken on Type A Manograph.

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.

Fig. 5—Type BC Manograph, Used Attached to Rod Meter Ready for Operation

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.

Fig. 7—Chart Showing Effect of Survey on Different Water Survey Areas

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.

Fig. 8—Organization Chart of Water Survey Division in Washington, D. C.

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.

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Water Waste Prevention Survey*

1

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

PAUL LANHAM

Engineer in Charge Waste Detection

Washington, D. C.

The following paper by Mr. Lanham forms an interesting sequel to the articles published in the September, October and November issues of FIRE AND WATER ENGINEERING, on Water Waste Control in the City of Philadelphia, by William M. Crowe, Assistant Engineer, Bureau of Water, of that CITY.—EDITOR.

SYSTEMS of water waste prevention surveys as applied in the various cities and by the private companies engaged in that class of work are basically the same. That is, the old Deacon system of English origin with its division of the distributing mains into districts and the more or less complete analysis of the total flow, forms the foundation upon which have been constructed the somewhat elaborate and thorough detailed systems of the present day. Two branches of work naturally form the complete system. First must be determined the necessity for the surveys as indicated by the total consumption and per capita data for the whole plant, which must be divided and separate determination made as to which sections or districts of the city are in condition demanding attention. After this, of course, follow the detailed surveys within these sections by which the actual location and causes of the abnormal or wasteful conditions are determined.

The first and probably most important step in starting a water survey of a city distribution system is the proper division of the mains into permanent districts. This necessitates a thorough study of the general layout and some knowledge of the direction and rates of flow in the different trunk mains. These latter facts may be easily determined by using portable pitot tube apparatus at various points. In selecting boundaries for the various permanent districts it must be borne in mind that measurable velocities are necessary at the proposed district measuring points, that valve closures must be made at neutral or nearly neutral flow points to avoid serious interference with pressure and supply, that subsequent work makes the segregation of like consumers in the same district not only desirable but almost necessary, that ample capacity must be provided in mains feeding the district when other mains are closed off during the measuring periods, and that the districts must be of such size as to permit a complete detailed survey within a period of one or two months to avoid confusion of data due to changes of season while the work is in progress.

These points cannot, of course, be literally carried out in all cases. High and low service areas interfere, some sections have natural boundaries which must be followed regardless of the dictates of the system; and intermixtures of factories with residences in many cases produce undesirable conditions. Permanent boundaries, however, must be established as near as possible in conformation with the plan and must thereafter be maintained permanent to avoid rendering useless for comparative purposes data previously secured.

Fig. 2—Index Cards Showing Method of Filing Data Note improvement in conditions shown by comparison of data before and after survey

*Excerpts from a paper read before the annual convention of the New England Water Works Association, at Albany, N. Y.

Fig. 1 Upper—Typical manograph chart showing flow through 30 main supplying purely residential section. Note night rate is about 80 per cent, of mean daily rate.Center—Flow chart showing rate through 42 main. Note peak during noon hour, which is an unusual condition. Note morning peak and rapid decline in flow rate after supper hour and after eleven o’clock at night.Lower—Night subdivision test chart showing effect of cutting off different squares for test. Taken on type B. C. Manograph.

Measurement of district flow should be made at as frequent intervals as possible. It would be ideal to maintain permanent recording instruments at the measuring points and keep constant record of the flow condition. This is impractical because of the extra fire hazard and other risks involved in maintaining a great number of closed valves throughout the system. From four to six measurements of at least seven days’ duration should be made if possible of the flow into each district each year. Portable recording pitot apparatus, which must be used upon the detailed flow analysis within each district, is ideally adapted to these measurements and its use for both purposes simplifies the equipment considerably. These measurements give mean daily consumption, maximum, minimum and night rates of flow. Population count made by the inspectors while making the detailed surveys within the districts permits the district per capita rates to be determined. The per capita rate and the ratio of the night rate to the mean daily rate of flow are excellent indices of the condition of the district. Of course, consideration must be given to the character of the consumption when reaching conclusions based upon these figures. To facilitate this, a census of buildings is also taken during the progress of the detailed surveys and this data together with all other must be recorded permanently for future reference.

Interesting Facts from Flow Charts

Most interesting facts are frequently brought out by study of the flow charts taken upon the various districts and their value is limited only by the intelligence of the investigator. Cases on record show districts where the night rate of flow exceeds the rate during the daytime, others show a ratio of night rate to mean daily rate varying from zero to 100 per cent. Charts frequently show abnormally abrupt changes in the flow rate, excessive peak loads indicating over-taxation of certain mains, and many other facts which have definite causes and reveal, upon study, all the secrets of the distribution system. Extreme variation in conditions will occur due to variation in usage in industrial plant, season changes and other causes, so that the data obtained must if possible be compared with previous data obtained under like conditions to determine its full import. The upper illustration (Fig. 1) shows a typical district of almost purely residential nature. Note that flow chart taken on a 30-in. main supplying a permanent rate is almost 80 per cent, of the mean daily rate.

The center illustration (Fig. 1) shows a flow chart from a 42-in. main supplying a large area. Note the usual morning peak load occurring in this case at 8:00 o’clock. Note also the peak during the noon hour which is rather unusual. Rapid decline in rate of flow after 7:00 P. M. and again after 11:00 P. M., give insight into the habits of the consumers.

Comparison of Conditions Before and After Survey

A comparison of conditions immediately before and after a detailed survey is particularly interesting and valuable. and the dates of measurements may advantageously be selected to permit this. The upper illustration (Fig. 2) shows an index card taken from the files of Washington, D. C. At the top of this card is given the total and per capita consumption. The high percentage of night rate and extremely high per capita consumption both show the necessity for waste investigation. The other figures on the card show the result of the detailed investigation. All flows detected on the night analysis are classified and recorded as shown on the lower part of the card. The improvement resulting from the detection and elimination of the waste is shown on the upper part of the next card, lower (Fig. 2). Further detailed surveys are recorded upon this card and the work is continued until the measurements show satisfactory conditions. In a number of cities different water service areas supplied directly by individual pumps or by trunk lines where Venturi meters have been installed constitute natural permanent districts which can be observed at all times either by inspection of the pumping records or the Venturi charts. In many cases these natural districts are too large to be properly treated as permanent survey districts but they form convenient units for checking total figures obtained by consolidating the data secured upon the permanent districts within their limits. Such data as mean daily consumption, per capita consumption and night rate of flow for the entire city should be plotted constantly as a matter of general interest and value. These figures are usually obtainable from pumping station or filtration plant reports. They form the measure of the effectiveness of the surveys and are indisputable. The graphic chart (Fig. 3) is the best method of recording this data as improvement or decline in condition is instantly observed without recourse to figures.

Detailed Surveys for Treating Wastes and Leaks

Detailed surveys within the permanent districts, made for the purpose of actually locating and weeding out the wastes and leaks from the legitimate consumption, follow a well-defined basic system also, but the degree of thoroughness and success depends greatly upon the limitations of the pipe system in the matter of valves and stop-cocks, and the abilit yof the operators. Measuring points having been established throughout the permanent district under survey, the portable recording pitot apparat_____s is moved from place to place as the work progresses and each section of main is given close examination. Small temporary test districts are isolated after 11 o’clock at night and the total rate of flow into them observed and recorded on the pitot chart. Work of testing and inspecting is continued through the night up until about 4 o’clock A. M., when it is found that the rate of flow becomes unsteady and interferes with the tests. Tests are made at this time because legitimate consumption is then at a minimum, while leaks and wastes will still be running at full head. In residential sections the rate during these hours is practically 100 per cent, illegitimate.

The method of test consists simply of measuring the rate of flow into a limited number of squares and noting either the increase or decrease in this rate caused bv altering the number of squares included in the test district. By “squares” is meant each section of the main in a given street lying between adjacent intersecting streets. In most cities valves are placed at these points. Of course the location of valves really determines the extent of the main included in each separate test. To go into detail, assuming a rate of flow of 100,000 gallons per day, for instance, in a test district of two squares, the rate of flow increasing to 110,000 gallons upon the addition of another square indicates, of course, that the rate of flow into this additional square is 10,000 gallons daily or the difference between the rates before and after its addition. Reversing the process the rate would, of course, drop from 110,000 gallons to 100,000 gallons, if the square is excluded from the test district. Both methods of testing are utilized as conditions require. The method of adding squares is preferable as it keeps the size of the district under test always at a minimum, thereby facilitating the work by frequently excluding for longer periods undesirable fluctuation in certain squares, also by immediately locating this fluctuation upon its appearance upon the chart coincident with the addition of a square under test, permitting the immediate exclusion of this square to avoid its interference with other tests. The lower chart, (Fig. 1) shows a typical one taken upon a subdivision night test. Note the changes in flow rate occurring coincident with the valve operation. Also note the high momentary rate coinciding with each valve opening due to rapid flow into an empty or partially empty main. This indicates that the main was tightly shut off preceding the test and verifies the existence of a leak or waste in the square.

(To be continued)

The Senate District Committee has reported favorably on the Zihlman bill, which provides for a commission to investigate and report on the available water supply for the District of Columbia. Unless new sources are opened up, engineering experts informed the committee, the district will soon face a serious shortage. The commission appointed will be directed to report at as early a date as possible.

Fig. 3—Graphic Chart Showing Method of Recording Important Data Bearing upon Condition of City Distribution System