Most canals with concrete linings have joints at regular close Intervals to control cracking of the concrete as a result of shrinkage and thermal movements. Whereas such canals are usually taken out of service for regular maintenance of the joint sealants, the Rand Water Board's Zulkerbosch raw water supply canal was designed to operate continuously. The concrete lining was therefore designed to have no joints at all, with the size and spacing of the cracks controlled by high tensile steel wire reinforcement in accordance with the then newly published British Code BS 5337 for water retaining structures. Crack spacing and crack widths were found to be larger than the values calculated according to BS 5337. Nevertheless a concrete canal lining without joints was shown to be a workable proposition.