Ancient drains

I’ve just laid 35 feet of new drain from the house down to the pond, and discovered a layer of what seem to be 18th or early 19th century drains, of a type that a little internet research discovers were named horseshoe drains. I have often noticed, whether at Greek ruins or at Norman Castles, that the remains of old drain and sewage systems fascinate visitors, myself included, so the annoying fact that one of our key drains was totally clogged with tree roots at least produced something nerdishly interesting.

Chris at the start of the dig, willow roots from the pipe draped over the fence

The worst roots had invaded from a vigorous willow by the pond, which had found its way up a section of plastic pipe I used a few years ago to extend the old drains when we changed the shape of the pond bank. The roots were an almost solid mass, and though they pulled out of the smooth plastic they would not budge from the clay pipe; as I dug further, I found the clay pipes, which were in short sections with gaps between like land drainage pipes, had also attracted the roots of several other nearby trees.

There was no alternative to digging the whole lot up, which needed a trenching spade and a pickaxe and a lot of hard work, because the pipes were 3 feet down and when I started the clay was baked hard as rock – which at least stopped my extremely narrow cut from collapsing, saving me from moving an awful lot more material.

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Half way, waiting for the lettuces to finish before digging through the vegetable patch!

Part way along, the modern looking yelow clay drains went into and through what appeared to be much older and more massive drains made of red clay. These had rough walls two inches thick and did not appear to have any bottoms. They were like an inverted U shape. They were much wider than the more recent drains, and the edges disappeared into the soil; it looked like the farmer had laid the new drains through what was left of a much older pipe, or relaid the old pipe on top.

Their odd shape turns out to be the source of their name: they are the so-called horseshoe drains, which came in a variety of forms, and were popular in the 18th and first half of the 19th century before ways were found to make completely round pipes cheaply in mid-century.

A section of horseshoe drain, and a piece of the pipe that was inside it.

Sadly, there was no practical alternative to breaking them to clear the way for a new drain. To have dug them out would have doubled or trebled the amount of spoil I would have to remove, because they were much wider than the new 4 inch flexible plastic drain I am laying. It would not have been possible to put the new pipe through the old drain, because someone had already managed to do that with the more modern round clay drains, which also had to come out, and which could only be got at through the ancient ones. I’ll measure the pieces and keep a record, though.

The pipes go to an old metre-deep brick sump by the house, through which rainwater from the roof flows, though its excessive size for rainwater makes me suspect that the function may have been more agricultural. It was right next to the dairy and the well and close to the cowshed. The pond must have been smelly.

We adapted this drainage system to be the overflow for the well, where we installed an automatic pump with a dual purpose – mainly to top up the pond in dry weather but also to keep the water table down, because in the winter the well water is otherwise on a level with our lowered kitchen floor nearby. The limecrete kitchen floor, built on a bed of expanded glass balls that acts as a drainage sump, was so well designed that there was never the slightest evidence of damp for the several years before we installed the pump, after belatedly noticing how high the well water came. It was probably unneccessary, but has turned out useful for the pond. Belt and braces reassurance.

The trench took about two full days to dig, spread out over several days, and the 100mm unperforated land drain pipe was delivered from JD Pipes in a 25 m coil, the smallest available. The bed of the trench was checked to make sure there was still a continuous gentle slope, using a spirit level resting on a long pole.

Gravel covers the new pipe
Filling begins

The pipe was then covered in more shingle and the trench backfilled. Turves cut from the surface before digging have been kept and will be relaid. At the pond end, the pipe now extends into the water, to avoid those willow roots, and will be protected by putting it through an old hard clay pipe, once the water level has gone down enough to do the finishing work. At the sump end it is fixed inside the large old pipe exit in the brickwork with quick drying cement of the type used for repairing concrete ponds.

Postscript

The link below is to a catalogue with drawings of a collection of old land drainage pipes put together by the Ministry of Agriculture during a campaign in the 1940s to improve farmland. The document is old but it says the pipes went to the Museum of Country Life, though the nearest I can find in the UK is the Museum of Rural Life in Reading. It is hard to imagine a narrower and more obscure subject for a collection, but if you’ve just dug down to find some I can vouch for the nerdish interest it arouses.

Link to document on field tile collection