IMPLEMENTATION OF PRESSURE MANAGEMENT IN MUNICIPAL WATER SUPPLY SYSTEMS

Pressure management is one of the most important Water Demand Management interventions that can be implemented by a water utility in its efforts to reduce leakage. Since leakage is driven by pressure, any efforts which result in the reduction of water pressure for even part of the day will reduce the leakage to some extent. Despite the obvious benefits that can be derived through proper pressure management, relatively few water utilities around the world are in fact implementing any form of pressure control. If implemented correctly, pressure management can be successful in reducing leakage from existing and new burst pipes as well as reducing the hidden and often overlooked background leakage. In certain circumstances, pressure management can also result in a significant reduction in the “normal” consumption and will have the hidden benefit of extending the lifespan of the reticulation system. With so many positive aspects to pressure management it is therefore surprising to find that many water utilities around the world tend to shy away from such measures for a variety of reasons, most of which are based on popular misconceptions. Virtually every water supply system which is operating on a full 24-hour pressurised supply has some scope for pressure management whether or not it is a flat area or very hilly. The paper will provide additional information on the key issues to be considered when contemplating the implementation of pressure management. It will also explain the basic concepts of advanced pressure control where pressures are controlled using electronic or hydraulically operated modulating devices which provide greater flexibility and this also greater savings. The paper will conclude with some details from several of the largest advanced pressure control installations implemented in the world. These installations are fully operational in South Africa and have been widely recognised as some of the most significant water demand management projects of their type in the world. The paper discusses some of the key issues that must be considered when assessing the scope for pressure management from a practical viewpoint based on the experience gained through the implementation of over 200 installations. It addresses specific problems that were experienced in the implementation of the Khayelitsha installation in Cape Town as well as the Sebokeng installation in Gauteng, both of which supply water to over 500 000 residents through a single installation. The new Mitchell’s Plain installation in Cape Town will also be discussed which supplies water to a similar sized community and was only commissioned towards the end of 2008. Between these three installations, savings of over 20 million kilolitres of water are achieved each year representing more than $6 million per annum.