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Roman Plumbing at Isca

September 15, 2011

“It is to be observed that the pipes take the names of their sizes from the quantity of digits in width of the sheets, before they are bent round: thus, if the sheet be fifty digits wide, before bending into a pipe, it is called a fiftydigit pipe; and so of the rest.”

Marcus Vitruvius Pollio: de Architectura, Book VIII

The word plumber dates from the Roman period, in Latin lead is plumbum; those that worked the lead, the plumbers, were known as the  plumbarii and of course the symbol for lead is Pb in the periodic table.

“Dave, you’re in trench six today with Rob, is that ok?”

At first I thought that was a joke for I knew what was in trench six. Quite unashamedly, I wanted a part of it. It had been unearthed some days earlier and Time Team had already been in there so that they could be filmed having a little crack at it. Its how television works. I knew lead pipe had been found at Caerleon before, an eleven metre section had been recovered from the School Field excavations in 1928, but to be part of this one was an amazing, selfish, opportunity.

Lead water main, 17cm gauge, School Field, 1928

Funnily enough, even though I knew what had been found I hadn’t had the time to go and actually see it until the night before I ended up in the trench. We had been so busy in trench two that the other trenches had no concern for me. The pipe had been adequately protected by a plastic sheet.

Lead pipe

The spur interested me, to see a welded joint from this period that was obviously still in-situ is rare indeed. To have a spur of a smaller bore to the main pipe was even better. When a water system is gravity fed, as this one would have been, there are two ways to increase pressure. The most obvious way is to increase the incline of the pipe so that the water runs through it at a faster pace. The other way of achieving pressure is to tap the main pipe with a smaller bore. The pressure from the larger bore is immediately increased. This is what we appeared to have in this instance. The big question was why? The favourite theory was that it led to, and then, powered a fountain. Well, did you expect anything else?

With the plastic removed, a quick clean of what what was there began to give a better insight into what we had.

So, not only did we have a smaller bore but it appeared to be falling at a steeper angle to its larger supplier, increasing the pressure even more. As you can see (at the bottom of the picture) the pipe had a wall constructed around it and it was the other side of this wall that had to be excavated next to see if the remains of the pipe continued or had it been robbed out in antiquity.

This turned into quite a difficult task. There was not much room to play with, I couldn’t really place my feet on the wall as it had been semi cleaned, rendering the masonry unstable, and the extension to the trench was not at all large for somebody of my height. To top it all off the local media had published that Time Team were going to be present over the Bank Holiday weekend. They weren’t, they had left on the Friday but the hoards of public visitors increased no end. As much as you concentrate on the job in hand, having between 20-50 members of the public standing at the edge of a trench you are working in does slow you up. Its a distraction. Nevertheless, if it was not for the public tours the next picture would not have been possible. Thank you Lynda, you’re a darling.

It was incredibly cramped in there!

With your ankles next to your rear end, your knees next to your chest, and having to concentrate on what your trowel reveals, is a tiring exercise. After carefully excavating what was in front of me, I had to turn around and excavate what was behind me – without disturbing what I had just uncovered, or the remains of the wall. My knees went first, the back second but I didn’t tell anyone; determination carried me through. I am glad it did, the pipe did carry on but not as we thought it may have. It had collapsed at some point which meant that it was at a much lower level than expected.

Next up was the cleaning of what you can see in the right hand side of the photograph above. That was going to be at the forefront of the photograph for publication. The key with that is that you carefully remove all of the soil that is around the masonry without disturbing it whatsoever. For sure you will disturb one or two of the smaller stones but by and large they have to be kept intact, removing them would destroy any possible hope you may glean of understanding the construction and/or the collapse of what was there. The majority of this was achieved using a small implement known in archaeological circles as a leaf and square [trowel], they are tiny.

It was the most painstaking but rewarding work I have ever done, The resulting pictures should give you a clue as to how it turned out.

 


The day after I was sent to another trench. I never did get the opportunity to de-construct the overlying wall, which was a shame. But that’s the thing with a training excavation, there is no ‘I’ in team, other students had to have the opportunity to finish off what I was lucky enough to have started. Before I had even got to trench six there had been a hoard of students and volunteers slaving away in there, for weeks on end. I believe that I was the lucky one to have been able to clean the pipe up. That’s life I guess. Some you win, some you lose.

The pipe was fully excavated by the time the trench was closed down. Take a look.

Next up, lets go back to the CBM and the Legionary Fortress’ of Wales – That will be a big pile of fun.

MD

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  1. The Fortress Baths at Isca « monasticdave

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