Hierdie verhandeling handel oor Nie-verrekenbare water (NVW) van pypnetwerkstelsels, oorsake wat daartoe lei sowel as die verskillende faktore wat daarby betrokke is. Verskillende wyse waarop die NVW van 'n netwerk bepaal kan word, word ondersoek en metodes vir die vermindering van NVW word bespreek. NVW van pypnetwerkstelsels bestaan uit vier komponente. Sekere van hierdie komponente is van groter belang, veral werklike verliese, as ander. Die volgende vier komponente kan onderskei word: <ul> <li>werklike verliese as gevolg van lekkasies wat ekonomies herstelbaar is</li> <li>onvermydelike verliese as gevolg van klein lekkasies wat nie ekonomies herstelbaar is nie</li> <li>oënskynlike verliese as gevolg van stadige perseelmeters aan die leweringskant</li> ongemeterde aftrekkings deur brandkrane en spoelkleppe.</li></ul> Watermeters en hulle akkuraatheid het 'n baie definitiewe invloed op die NVW van 'n netwerk. So byvoorbeeld kan daar 'n aansienlike toename in die NVW voorkom indien meters nie die korrekte volumes wat deur hulle vloei, registreer nie. Pypmateriale en konstruksiemetodes het 'n invloed op NVW en is ondersoek. Indien lae kwaliteit materiaal gebruik word en verkeerde installasie metodes gebruik word lei dit tot meer lekkasies en 'n hoë NVW. Lekkasies in 'n netwerk het 'n invloed op die NVW. As gevolg hiervan is verskeie metodes van lekkasie opsporing ontwikkel. Hierdie verskillende metodes van lekkasie opsporing is in die veld ondersoek om sodoende die bruikbaarheid en geskiktheid van elk te evalueer. Resultate van hierdie ondersoeke dui daarop dat 'n kombinasie van metodes die mees geskik voorkom vir lekkasie opsporing en waterverliesbeheer. Hierdie metodes bestaan hoofsaaklik uit visuele naspeur, soniese sporing sowel as verliesvloeimeters. ENGLISH : The Subject of this thesis is Unaccounted for Water (UAW) of Water distribution Networks. Various causes and factors are responsible for the UAW of networks. These have been studied together with various methods of control. Four components make up the UAW of networks with some being of bigger importance, especially actual losses, than others components are: <ul> <li>actual losses due to leaks which are economically repairable</li> <li>unavoidable losses due to small leaks which are not economically repairable</li> <li>apparent losses due to underregistering stand meters</li> <li>unmetered draw-offs via hydrants and flushing valves.</li></ul> Water meters are used to determine the UAW of a closed network by means of measurements on both sides of the network. Inaccurate slow meters can be the cause of the UAW being much larger than otherwise. Pipe materials and construction methods have been studied in as far as it concerns the UAW. Low quality materials and bad construction methods lead to increases in the UAW. Leaks in a network have an influence on the UAW and therefore various methods of leak detection have been developed. Field investigations concerning these various leak detection methods were carried out and these methods were evaluated. From results of these field investigations it became clear that a combination of methods was most suitable for leak detection and water loss control. These methods include the visual method as well as sounding devices and waste detection meters. / Dissertation (MSc)--University of Pretoria, 1978. / Chemical Engineering / unrestricted