In 70 he was praetor, and five years later was sent into Britain to succeed Quintus Petillius Cerialis as governor of that island. He subdued the Silures and other hostile tribes of Wales, establishing a new base at Caerleon or Isca Augusta for Legio II Augusta and a network of smaller forts fifteen to twenty kilometres apart for his auxiliary units. One of these would have been the fort at Luentinum where it controlled the gold mine of Dolaucothi, and was worked by numerous aqueducts. He was succeeded by Gnaeus Julius Agricola in 78.
In 95 he was appointed Water Commissioner of the aqueducts (curator aquarum) at Rome by the emperor Nerva, an office only conferred upon persons of very high standing. He was also a member of the College of Augurs. He produced an official report on the state of the aqueducts serving the city of Rome towards the end of the first century AD, the first official report of an investigation about engineering works ever to have been published.
In this capacity he followed another distinguished Roman statesman, Agrippa, who organised in 34 BC a campaign of public repairs and improvements, including renovation of the aqueduct Aqua Marcia and an extension of its pipes to cover more of the city. Through his actions after being elected in 33 BC as one of the aediles (officials responsible for Rome's buildings and festivals), the streets were repaired and the sewers were cleaned and renovated. Agrippa signalized his tenure of office by enlarging and restoring the Cloaca Maxima, the main sewer in Rome, constructing thermae, porticos, and laying out gardens.
His chief work is De aquaeductu, in two books, an official report to the emperor on the state of the aqueducts of Rome. It presents a history and description of the water-supply of Rome, including the laws relating to its use and maintenance. The history of all the aqueducts of Rome is described including details of the sizes of the channels and discharge rates, such as Aqua Appia, Aqua Alsietina, Aqua Tepula, Anio Novus, Aqua Virgo, Aqua Claudia and Aqua Traiana. He also describes the quality of water delivered by each, mainly depending on their source, be it river, lake or spring. One of the first jobs he undertook when 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, amongst 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. He was well aware of the seminal work De Architectura by Vitruvius which mentions aqueduct construction and maintenance published in the previous century, classing him at one point with "the plumbers".
The latest edition of the Stratagems is by R. I. Ireland, Teubner, 1990; English translation in Loeb Classical Library, 1925. Extracts from a treatise on land surveying ascribed to Frontinus are preserved in B. Campbell, The writings of the Roman land surveyors: introduction, text, translation and commentary (London, 2000).