The Siphon

The Siphon

Stream siphon
Alvingham mill stream

The English village of Alvingham in Lincolnshire was settled around 750 AD. In 1537, King Henry V!!! granted land for a mill in the village, and a mile-long mill stream was dug from the River Lud to supply its water wheel with power. In 1770, the Louth Navigation Canal was built from the small town of Louth to the North Sea near Tetney. One of several locks was built at Alvingham, where the canal also had to cross the mill stream dug some 230 years earlier.

Siphon location detail

After negotiation, some-one with an active engineering mind suggested a siphon be built to carry the water of the mill stream underneath the canal. A five-foot diameter brick tunnel was built that descended from where the mill stream approached, down under the canal and came up on the far side. This allowed the water to continue flowing in the mill stream without interference to the canal operation. Money to cover the disruption was paid to the mill owner who completely rebuilt his mill in 1783, and it still stands to this day, although for the last forty years only as a tourist attraction.

Section through siphon

The locks were built immediately east of the siphon area, along with a large unloading yard where the freight could be taken from the barges by horse and wagon. The Ship Inn, complete with brick beer cellar, was also built to provide refreshments and overnight accommodation if needed. The canal use declined in the mid 1800’s and eventually closed as the transportation of goods was taken over by the advent and spread of steam railways. The Ship Inn business also disappeared and it became known as Lock Cottage with the owner farming property around the area that had been acquired over the years. The unloading yard became the home yard for the farm as additional animal and storage barns were built.

Alvingham Lock 1910

That farmhouse was where I grew up, and the brick cellar, still there, was used for food storage. In retrospect, I greatly admire my mother’s stoicism, as her children were exposed daily to the hazards of the open entrance to the siphon tunnel at one end of our house lawns, and the deep unprotected drop into the locks on the other side of the yard. Amazingly, only one of us ever fell into the canal lock, and fortunately, was quickly rescued by a farm hand who was working close by. The lock gates were removed from the canal in 1943 when the local township excavated the accumulated mud out of the canal to facilitate better water drainage.

entrance to siphon

The siphon had continued supplying the mill with water, untouched, until accumulated silt caused a partial blockage of the tunnel around year 2000. The water stream was blocked off, the tunnel pumped out and almost 250 years of accumulated mud and objects was cleaned out. The brick tunnel itself was still in great condition, a tribute to those long ago construction workers. At the same time as it was cleaned out, and in keeping with today’s standards of safety, vertical bars were installed at the tunnel entrance to prevent anyone from accidentally being drawn in. Don’t know how I survived my boyhood without them!

To this day, it is an outstanding 250 year old memorial to those “out of the box” thinking engineers who conceived and built it.  Although the principal is used fairly extensively, there are few examples of one this old still in continuous use.