One of the first jobs he undertook when he was appointed water commissioner was to prepare maps of the system so that he could assess their condition before undertaking their maintenance. He says that many had been neglected and were not working at their full capacity. He was especially concerned by diversion of the supply by unscrupulous farmers and tradesmen, among many others. They would insert pipes into the channel of the aqueducts to tap the supply. He, therefore, made a meticulous survey of the intake and the supply of each line, and then investigated the discrepancies. Lead pipe stamps bearing the name of the owner were also used to prevent such water theft. He was well aware of the seminal work "De Architectura" by Vitruvius, which mentions aqueduct construction and maintenance published in the previous century; Frontinus refers to the possible influence of Vitruvius on the plumbers.