The Delikkemer Siphon of the Patara Aqueduct is remarkably intact - the pipe is on top
Talking about Patara’s siphon yesterday made me wonder whether it was made with lead as the siphon in Arles which crossed the Rhone and brought fresh water to the town. A few years ago, I noticed the remaining lead pipes in Arles’ Museum of History. These pipes were nicely exhibited but only a few visitors noticed.
These Lead Pipes in Arles were used for the Siphon that crossed the Rhone in Roman Time
The siphon in Patara is 22.7 km long and crosses a small valley about half way. Siphons work by pressure equalization between two connected reservoirs or containers when using an airtight connection. In the Swiss Army, we often used this principle to transfer diesel from tanks to other vehicles when far away from gas stations. All you need is a plastic hose.
Man of the Patara Aqueduct - the Siphon is between P1 - P2
Wonder how the Romans could make their siphons airtight. They often used lead as in Arles. Before answering the question, I want to say a few words about lead in the Roman Empire. For people who know about lead poisoning, the use of lead pipes for water distribution is unacceptable. Though, until a few decades ago, lead pipes were common in Europe and America.
There were more than 2'500 Aqueducts in the Roman Empire - many used Lead
Lead or plumbum in Latin, which gave us the English word for plumber, was the second most frequently cast metal in Roman time. Every year 80’000 tons were produced. Iron ranked first with 125’000 tons, copper came third with 15’000 tons, followed by silver (200 tons) and gold (9 tons). The reason for lead’s omni-presence was its association with gold and silver mining – it was a useful byproduct.
Mining Activity in the Roman Empire - Sea Lanes linked all these Operations smoothly
Lead production in the Roman empire was concentrated on the Iberian peninsula, the British Isles and Dacia (Romania). Some historians argue that Rome’s appetite for tin (to make bronze) and lead (for their water systems) led to England’s conquest in the first century AD. Julius Caesar had invaded the island a century earlier but saw nothing that would justify a permanent occupation. Eventually, Rome had to keep 3 legions (10% of its field army) in Britain to pacify these unruly Celts. And to get some lead and tin.
The Boat found in Mal de Ventre was 9 m wide and 30 m long -
the Dragonfly is 7 m wide and 39 m long
Lead was heavy. There were reinforced ships for its transport. As luck has it, divers found in 1988 one of these boats off the island of Mal di Ventre 10 km from Sardinia. There were 1’000 triangular, 45 cm long lead ingots on board, each weighting 33 kilograms, or 33 tons in total. We have no indication of the lead’s destination since most of the ship disintegrated after it sunk around 80 BC. But the finding illustrates how Romans used lead on a very large scale. The pollution which this wide spread use caused is measurable in the ice cores of Greenland – 2’000 years after it happened.
Divers labelling Lead Ingots in 20 m Depth before bringing them to the Surface
Lead had many advantages. As a mining byproduct it was cheap. Its densely packed atoms made it heavy but still malleable. It is not corrosive, does not rust, needs no maintenance. It was perfect for sealing roofs or making pipes. Romans knew that lead is poisonous and leads to brain damage. Several authors wrote about it.
Lead Pollution in the Ice Cores of Greenland
Luckily for the Romans, they lived in a mostly lime stone environment - Europe’s south was folded from limestone sediments from the Tethys sea. This considerably reduced lead's poisonous impact. Limestone dissolves in water and quickly lines lead tubes with calcium. The thin calcium layer thus separates lead and fresh water. The limestone layer also absorbs the most dissolvable form of lead (type II) to an amazingly high degree. When lead gets in touch with copper though it galvanizes and releases unacceptably high levels of lead (type II again). This holds true today as well. A water pipe made from pure lead (type 0) carries less dissolved lead (type II) than a pipe which is 50% copper and 50% lead. Something people have to learn again when replacing old pipes. You need to go all in or leave the pipes untouched.
Three of the 1'000 Lead Ingots found off the West Coast of Sardinia - each weights 33 kg
It turns out that the Patara siphon was made without lead. Precisely chiseled stones were lined with ceramics and then joined. This method was strong enough to resist the increased water pressure in the siphon but – of course – broke during earth quakes. In 68 AD, this is exactly what happened. Patara was for three years without water. But the repairs were well done and kept the city supplied for more than 300 years before it broke again.
The Patara Aqueduct with its precisely chiseled and Ceramics lined Pipe
Never thought that lead was the 2nd most frequently used metal in the Roman Empire. Some scientists believe that the madness of some emperors was due to lead poisoning. Knowing the story of Nero who delighted in burning Rome and then blamed and killed Christians to cover it up – amongst them Saint Paul - gives this theory some basis. Maybe lead poisoning indirectly helped spreading the Gospel. What is definitely true is that the limestone from the Tethys Sea or plate tectonics saved the Romans from widespread lead poisoning,
Making Lead Pipes during the Roman Empire
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