Significance of losses in water distribution systems in India

Bulletin ofthe World Health Organization, 61 (5): 867-870 (1983) ©) World Health Organization 1983 Significance of losses in water distribution systems in India V. RAMANI Effective management of water supply systems consists in supplying adequate quantities of clean water to the population. Detailed pilot studies of water distribution systems were carried out in 9 cities in India during 1971-81 to establish the feasibility of a programme of assessment, detection, and control of water losses from supply systems. A cost-benefit analysis was carried out. Water lossesfrom mains and service pipes in the areas studied amounted to 20-35% of the totalflow in the system. At a conservative estimate, the national loss ofprocessed water through leaks in the water distribution systems amounts to 1012 litres per year, which is equivalent to 500 million rupees. It is possible to bring down the water losses in the pipe mains to 3-5% of the totalflow, and the cost incurred on the control programme can be recovered in 6-18 months. Appro- priate conservation measures will help in achieving the goals of the International Water Supply and Sanitation Decade to provide clean water for all. Effective management of water supply systems consists in supplying adequate quantities of clean water to the population. So far, little attention has been paid to water conservation in most of the water supply systems in India. The reasons for this indiffer- ence may be attributed to a lack of awareness of the direct and indirect benefits to be gained from routine, preventive maintenance, and to a lack of funds for staff and monitoring equipment. Detailed pilot field studies of water distribution systems were carried out in 9 Indian cities, using specialized field techniques and scientific procedures, at the initiative of the National Environmental Engineering Research Institute, Nagpur. Surveys were done in Ahmedabad, Aurangabad, Bombay, Calcutta, Jaipur, Lucknow, Madras, New Delhi, and Surat, during the period 1971-81 to establish the feasibility of assessment, detection, and control of water losses in mains and service pipes. A cost-benefit analysis was carried out. The approach adopted re- quired careful planning and preparatory work, and was very labour-intensive and time-consuming. Loss of water from a distribution system can occur as a result of: - leakage from reservoirs; - leakage from water mains through faulty joints or corrosion; - leakage in service pipes and fittings inside or outside the consumers' premises; - leakage through abandoned service pipes. Head, Environmental Engineering Consultancy Division, Sewage Treatment Division and Water Distribution Cell, National Environmental Engineering Research Institute, Nehru Marg, Nagpur 440 020, India. These losses will be intensified if the pressure in the distribution system is unduly high. In addition to losses from the delivery system itself, consumers may waste water by failing to turn off taps when not needed, or using excessive amounts for washing vehicles, watering the garden, etc. It may be feasible to reduce such waste by education and by metering the consumers' premises. However, system losses must be assessed and controlled by systematic waste and leakage detection, followed by prompt corrective action. METHODS Leakage can be considered as the amount of potable water lost from a supply source in trans- mission and distribution, other than by deliberate or controllable action. The total leakage from the mains, laterals, and portions of service pipes or communication pipes to the consumers' premises was assessed for a zone of about 250-350 house service connexions. This was carried out by closing all the boundary valves and stop taps to the consumers' connexions, and allowing the water to enter the system through a single feeder pipe via a bypass meter. The recorded flow thus depicts the waste due to leakage in the mains. If the recorded waste flow was considered excessive, further tests were carried out to localize the leaks. This was carried out by a "step test", in which the size of the zone was reduced systematically, by closing the internal valves one by one, and the flow into the system noted at each 4351 -867 V. RAMAN step. By ensuring that the system was brought to a "tree" system (i.e., with no closed loops), the step- wise isolation of a zone or subzone of mains was achieved and the possible sources and extent of wastage through leaks could be found in a short stretch of mains pipe. The exact location of leaks was carried out at night, by means of sounding rods and/ or an electronic leak detector, after the exact align- ment of pipes had been determined using either exist- ing records or an electronic pipeline detector. This technique was possible wherever the supply to the sys- tem was intermittent. In cases where the supply was continuous, losses were reflected in the minimum recorded night flow. RESULTS The pilot studies in 9 cities revealed that 20-35G7o of the total flow in the water distribution system is lost through leakage from the mains, communication, or service pipes, and valves. This amounts to 40-85 litres per person per day. (The per capita water supply in Indian cities is between 100 and 200 litres per day.) The leaks also result in the deterioration of the quality of water (from aesthetic and microbiological aspects), possibly leading to the outbreak of water-borne dis- eases such as typhoid fever, hepatitis A, and gastro- enteritis. At a conservative estimate, the national loss of processed water through leaks in the water distribution systems amounts to 1012 litres per year, which is equivalent to 500 million rupees or approximately US$ 55 million (assuming that the average cost of processed water is 0.5 rupees per 1000 litres). In addition, there is a significant but unquantifiable economic loss as a result of public health problems arising out of the deterioration of the quality of the water in the network. Most of the leaks in the pilot zones in the nine cities occurred in house service pipes, communication pipes, ferrule connexions, and couplings; a few leaks were found in valves, mains pipes, and joints. The gal- vanized iron pipes were often found to be corroded, especially when they were in soils that contained clay, humus, and moisture. DISCUSSION Through a systematic programme of preventive maintenance of water distribution systems, it is possible to reduce losses from such systems to 3-5Wo of the total flow. There are noticeable improvements in pressure and flow of water from taps after leaks have been repaired. Obviously, improvements in water quality and flow lead to a reduction in the inci- dence of water-borne diseases. In setting up a maintenance programme, the aims should be to: 1. ensure proper installation, regular checking, care, maintenance, and calibration of meters and pressure gauges, so as to obtain correct and reliable readings; 2. develop a systematic approach to detection and control of water losses in the supply system, especially in transmission and distribution, and proper mainten- ance of valves, stopcocks, etc.; 3. maintain effective vigilance to detect and pre- vent unauthorized connexions to the system; 4. set up a field-oriented training programme for engineers, supervisors, technicians, and semi-skilled workers; 5. obtain the necessary instruments and equip- ment. Manpower and equipment requirements A separate division should be created in each water- works to carry out systematic checks of leakage and water quality. Each division should consist of the personnel shown in Table 1. One division should be Table 1. Staff required to carry out a programme of pre- ventive maintenance of a water distribution systema No. Staff required Responsibilities Assistant Engineer 1 Overall supervision and control of programme Overseer/supervisor Supervision of or junior engineer field work Chemist/bacteriologist 1 Analysis of water samples Valve operators, fitters, plumbers, and meter 8 Routine field work readers Instrument mechanic 1 Repair and care of instruments Field technician 4 Sounding and pipe alignment Draughtsman 1 Drawing and updating of plans of network Record keeper/clerk and 2 Office work typist Unskilled labourers 6 Assisting fitters and plumbers Driver 1 Transport a The monthly salary bill would be around 1 5 000 rupees. 868 LOSSES FROM WATER DISTRIBUTION SYSTEMS adequate for a city with a population of up to about 1 000 000; for larger cities, two such divisions, super- vised by a full-time executive engineer, will be required. For major repairs and replacement of pipes and valves, support should be obtained from oper- ation and maintenance and project departments of the water authority. Each maintenance department should also have the equipment listed in Table 2, the total capital cost of which is around 150 000 rupees. A jeep and trailer costing about 100 000 rupees is also essential for field work. An initial capital expenditure of about 250 000 rupees is therefore needed for equipment and trans- port. The annual expenditure for personnel and related items and project work would be 200 000 rupees. Allowing for a depreciation of 100%o, the recurrent costs for instruments and transport work out to 25 000 rupees per year. Table 2. Equipment required to carry out a programme of preventive maintenance of a water distribution system Type of equipment No. required Pitometer 1 Revenue (bypass) water-meters 3 Mobile waste-detection (bypass) meter 1 Electromagnetic pipe and cable locator 2 Electroacoustic leak detector 1 Valve box locator 1 Sounding rod and/or aquascope 1 Road measurer 1 Pressure gauges 4 Pressure recorders 2 2-way radio 1 Supplementary plumbing, joints, hose-pipes, etc. one set Financial implications The cost of water for domestic purposes is 0.50-0.80 rupees per 1000 litres. Assuming that an average of 25 litres of water per capita per day could be saved by a waste survey and detection programme, and that initially one division could cover a zone with a population of about 25 000, the immediate savings would be 0.5 x 25 000 x 25 x 365 = 114062.5 rupees per year, 1000 while the annual expenditure (including depreciation on instruments and transport) would be 225 000 rupees per year. In addition, unquantifiable benefits would arise from such programmes, such as improved pressure and flow to the consumer, updating of distribution system plans, consumer satisfaction, improvement in water quality, and associated reduction in health hazards. Table 3 provides information on the cost of waste assessment and control in the pilot projects. It may be noted that the expenditure incurred in the initial stages of the programme will be higher than that for subsequent work in the same zone, since much time, labour, and expenditure are involved in the detailed preparatory work. This consists in updating the distri- bution system plans, preparing an inventory of pipes, valves, connexions, and houses, providing valves and bypass arrangements, etc. CONCLUSIONS It is incumbent on each water authority to have a separate division with the necessary trained personnel and equipment, to carry out a continuing programme of preventive maintenance of water supply distri- bution systems. Table 3. Cost of waste assessment and control in the pilot projects, 1971-80 Total time taken Period of Labour Material Total recovery of Preparatory FieldCity Population cost cost Supervision cost expenditure work work(rupees) (rupees) (rupees) (months) (months) (months) Bombay 8 000 - - - 11 000 5.5 4 1.5 Madras 2 620 5 485 14 615 20 050 40 150 1.5 3 1.5 Aurangabad 6 180 1 169 5 330 2 495 8 994 20 3 1.5 Ahmedabad 3 260 9 330 18 200 2 000 29 530 18 4 1.5 Surat 8950 11 000 91 540 4000 106540 15-18 6 4 869 V. RAMAN In view of the goals of the International Water Supply and Sanitation Decade to provide clean water to all by 1990, conservation of water and preservation of water quality are of tremendous importance, particularly in view of the limited water resources available. ACKNOWLEDGEMENTS Thanks are due to Dr B. B. Sundaresan, Director, National Environmental Engineering Research Institute, Nagpur, for his keen interest and encouragement. RESUME IMPORTANCE DES PERTES DANS LES RESEAUX DE DISTRIBUTION D'EAU EN INDE Bien gerer les reseaux d'approvisionnement en eau, cela veut dire fournir en quantites suffisantes de l'eau propre a la population. Jusqu'ici, on ne s'est pas beaucoup interesse a la conservation de l'eau dans la plupart des reseaux d'approvisionnement en Inde. Des etudes pilotes detaillees des reseaux d'alimentation en eau ont et faites dans 9 villes indiennes a l'aide de techniques de terrain specialisees et de methodes scientifiques. 11 s'agissait d'evaluer l'aptitude des programmes a deceler et maitriser les pertes d'eau dans les conduites et les canalisations de raccordement. Une analyse couit/avantages a egalement et faite. L'approche adoptee, qui demandait une planification et des preparatifs soigneux, a pris beaucoup de temps et exige beaucoup de main- d'oeuvre. On a constate que les pertes d'eau dans les conduites et les canalisations de raccordement des villes indiennes representaient entre 20 et 35%7o du debit total du reseau. D'apres une estimation prudente, les pertes d'eau traitee dues a des fuites dans le reseau d'approvisionnement representent pour l'ensemble du pays 1012 litres par an, soit 560 millions de roupies. Or, un programme preventif d'entretien permettrait de ramener les pertes d'eau dans les conduites a 3-50lo du debit total. 11 faudrait notamment: - crer au service des eaux une division a part chargee de reperer et de maitriser les fuites; - obtenir des lectures correctes et fiables des compteurs et des jauges; - adopter une approche systematique et scientifique de l'evaluation, de la detection et de la maitrise des pertes d'eau; - assurer une surveillance efficace pour reperer et empecher les raccordements illegaux; - mettre sur pied un programme de formation oriente sur la pratique a l'intention des ingenieurs, des responsables de l'encadrement, des techniciens et des ouvriers semi- qualifies; - procurer les instruments et le materiel necessaires. Le cout d'un tel programme de detection et de contr6le des pertes pourrait etre recupere sur une periode de 6 a 18 mois; on devrait pouvoir ainsi contribuer a la realisation des objectifs de la Decennie internationale de l'eau potable et de l'assainissement, qui est de fournir a tous de l'eau propre. 870