How did Roman Aqueducts work? – an entertaining introduction to Roman engineering prowess and its support of Roman culture and values

Garrett Ryan, “How did Roman Aqueducts work?” (Toldinstone, 19 March 2022)

At last historian Dr Ryan tackles the topic every eager student of Roman civilisation wants to know: how did Roman aqueducts work, why did the Romans build aqueducts and how successful were the aqueduct systems? The aqueducts and their networks represent perhaps the peak of Roman engineering and the Roman flair for practical thinking and planning. Most of all, aqueducts fully represent how Roman values and lifestyles, centred around the city, were supported and maintained by Roman technological achievements.

Dr Ryan introduces his topic with a beautiful photograph of Rome’s famous Trevi fountain followed by other stunning visuals and a history of aqueduct evolution from Ancient Greek times through the Hellenistic era to the Romans who hit on the idea of using arched bridge technology to help bring spring water from hillsides and mountains to their cities. Dr Ryan stresses that aqueducts were not built to supply drinking water; instead they were built to supply water for public baths (sponsored by elites) and for private use by wealthy families. Building an aqueduct was actually a difficult and arduous process: the downward gradient of an aqueduct had to be gradual and gentle, and for this Roman engineers relied on specialised instruments to measure relative distance and height between two distant points and achieve ideal water levels. Aqueducts usually ran underground for much of their length, following the contours of the land. Arched bridges help to maintain the gentle downward gradients of aqueducts when they emerged from underground, and rows of arched bridges (such as the famous and spectacular Pont du Gard in France) might be built for such maintenance. In some valleys, Roman engineers might build inverted siphons if arched bridges could not be built.

When aqueducts reached the cities they were intended for, the water they carried – and they could carry up to billions of litres a day – ended up in primary distribution tanks and then secondary distribution tanks branching off from the primary ones. From the secondary distribution tanks, water would be piped to public baths, public fountains, factories and private luxury homes. Those who could afford having water piped into their homes applied to the Roman Emperor for permission to have a calix (a metal, usually bronze, connector; bronze was used as it was hard for thieves to tamper with) installed into a local secondary distribution tank; a pipe would be run from the calix to the customers’ homes. Water bills were paid based on the size of the calix. When customers died or sold their homes, the calix would be removed and the buyers would have to apply anew for a calix. Those who had water pumped into their properties often used the water extravagantly in the form of fountains, private baths and gardens.

Aqueduct maintenance was constant and often difficult; not all cities that had aqueducts cleaned them regularly and aqueducts often ended up clogged with mineral deposits carried by water.

Dr Ryan concludes his mini-lecture by noting outstanding examples of aqueduct systems that served cities long after the Roman civilisation fell in the 5th century CE. One such example is the aqueduct of Constantinople which carried water into underground cisterns in the city and which was maintained well into Ottoman times: the Ottomans themselves used the aqueduct to supply water to their imperial palaces and maintained, repaired and even extended the system.

As is usual with Dr Ryan’s mini-lectures on Classical civilisation in his Toldinstone series, this instalment is informative and entertaining, and illustrated with spectacular photos of aqueduct systems, diagrams and maps. The talk might have been longer and more complete if Dr Ryan had added something about how waste water was used to flush public toilets and to clean streets, and then disposed of in underground sewers and ultimately into rivers.

Surprisingly Dr Ryan touches very briefly on the topic of whether the lead used in aqueducts and the pipes attached to them might have caused lead poisoning that is presumed to have contributed to Ancient Rome’s decline. While the talk does not say whether the lead pipes did or did not, two things from the talk stand out: water was constantly moving from gravitational pressure through the aqueducts so it would not have picked up much lead; and (ironically) aqueducts not regularly cleaned would have been coated with mineral deposits like calcium carbonate from the water which would have prevented direct contact between the water and the inside lead pipe surfaces.

This mini-talk serves as an introduction to a fascinating aspect of Roman life, culture and technology, and how the technology serves culture and reflects it and its values. Viewers will be astonished that the aqueducts were not built to benefit ordinary working city people – the hoi polloi had to get their drinking water from public fountains, and use public baths and toilets – but instead to benefit the wealthy. The realisation that Rome was not a society structured around caring for people but instead around exploiting people hits hard indeed.