PUMP IT UP!
When the Grand Junction Canal opened, its Tring summit needed a water supply. It still does. We follow the story through 200 years to today’s pump upgrades
In an ideal world, canals wouldn’t need pumps to supply their water – and many don’t. Provided with adequate reservoirs, often tucked away high in the hills some miles away, they can draw on enough supplies by gravity alone to see them through a typical summer, before the winter rains replenish ther stocks.
Other canals are less well-equipped with supplies which over the years, as the canals got busier, needed to be supplemented with back-pumping schemes, returning water used by lock operation back up to the summit level for re-use. In recent years, the revival of the canals for leisure led to several of these systems being reinstated or new ones installed, for example enabling water to be pumped all the way east up the Kennet & Avon from Bath to the summit at Wootton Rivers, or right through from the Black Country to the southern Grand Union.
But there’s another possible reason for canal water supplies to need pumping – and not just in dry summers when it runs short. Occasionally, the local geography meant that it wasn’t possible to find water supplies (or to find suitable sites for reservoirs to store the water) sufficiently high up to feed the canal’s highest levels. There might be no alternative but to site the reservoirs at a level where water would need to be routinely pumped out of them and up into the canal.
We caught up with the Canal & River Trust’s Charles Baker, who is familiar with such situations. In his role as Senior Project Manager for the London & South East Region with a focus on mechanical, electrical and pumping equipment, he and his team have got two of them on their patch. They’re both the subject of current major works which, as he explains is aimed at keeping them performing their vital function by matching up modern technology (in the form of new electric pumps) to the historic infrastructure dating back to the days when the job was done by coal-fired beam engines.
One of these is on the Kennet & Avon, and results from a dilemma faced by the canal’s 18th century planners. Ideally they would have liked a long, relatively low level summit running all the way from Crofton through to Devizes, a distance of 20 miles at an altitude where supplying it with water by gravity from local springs and streams wouldn’t have been an issue. But that would have needed a tunnel 4312 yards long (which would have been second only to Standedge on the Huddersfield Canal as the country’s longest), adding to the cost, difficulty and time taken for the work. So instead, they opted for extra locks leading up to a shorter higher summit level with a much shorter tunnel – but that meant climbing to a height where no water supplies were available.
The solution was to raise water from a lower level (and later from a reservoir Wilton Water - constructed at that level) up to the summit by the celebrated Crofton Pumping station, whose restored beam engines still carry out their original function on certain summer weekends. For the rest of the time, the job is done today by electric pumps, but still using Wilton Water and still feeding into the same leat (water supply channel) leading to the summit level that was built to serve the steam pumps. CRT is currently part way through a programme of replacement of the electric pumping system in use since the canal was restored 30-plus years ago. Readers may remember that their reliability went under the spotlight a few years ago when the steam pumps had to be fired unexpectedly thanks to the failure of their modern replacements.
The project is divided into three stages: the first part, replacing the pipeline across the pumping station site, has already been completed. The second, the replacement of the electric pumping station, is due to take place this summer, with the final phase replacement of the pipe running under the canal bed from Wilton Water – due to start in the autumn.
At the same time, Charles describes a wider project known as “K&A Resilience” also under way. Up to now, the Crofton pumps plus the various backpumps installed
to recirculate water past the locks at Bath, Bradford-on-Avon, Seend, Semington, Devizes and Wootton Rivers have tended to be treated in isolation with bespoke solutions at each site. The limitations of this approach were shown up when one of the biggest pumps, raising water past the mighty 29-lock Caen Hill flight at Devizes, failed – and turned out to be pretty much the only pump in Europe of that particular combination of manufacturer, size and type. Repairs to the original being impracticable, a replacement was sourced, but it too is ‘on limited time’ regarding replacement parts. So the aim is to eventually replace all the backpumps with designs which are not only suited to the increased use since the system was set up, but have a high degree of transferability between sites.
But that’s something of a digression into backpumping. Going back to the issue of canals whose summit level cannot be fed by gravity and which therefore rely on pumping just to provide them with their regular supply from the reservoirs, we come to the second such example on Charles and his team’s patch: on the southern Grand Union at Tring. And compared to the simple system at Crofton of one reservoir, one pumping station and one canal, it’s a whole lot more complicated...
Once again, the geography dictated that a conventional reservoir feeding into the summit level wasn’t an option. The porous chalk ground conditions meant that there was very little in the way of streams or other surface water above the level of the canal’s three-mile summit (most of it in a deep cutting) from Cowroast to Bulbourne. Instead of reservoirs, a seven-mile feeder was built to bring supplies in from springs further west along the hillside near Wendover. To cater for trade from Wendover, it was built large enough to be navigable.
As trade on the new canal built up, this supply soon became insufficient to keep the canal going through the drier summer weather, so in 1802 a reservoir was built on a suitable site some way down the hillside from the Wendover Arm at Wilton. In wetter weather, it was fed by a channel bringing any surplus water coming in along the arm, plus some local springs - and in drier weather the stored water was pumped back up into the arm (and so to the main line) via a ‘heading’ (an underground culvert) leading from the bottom of the reservoir to Whitehouses, where a steam pump raised it up a well-shaft and into the Arm.
Such was the success of the canal that the increased needs for water saw three further reservoirs built over the next four decades – Startopsend, Marsworth and Tringford – plus two more providing increased capacity at the original Wilstone site. The new reservoirs were all fed by springs and by surplus water from the Wendover Arm in winter, while in summer two further pumping stations at Tringford and Bulbourne raised the stored water into the Arm.
In the late 1830s pumping was concentrated on the central station at Tringford, with new headings enabling it to draw water supplies from all the reservoirs, and the Whitehouses and Bulbourne pumps abolished. While this was a sensible rationalisation, it did create what we would now call a ‘single point of failure’ in the form of the single Tringford pump. So a second pump was added, pumping from a second well-shaft.
These two pumps satisfied the canal’s needs right up into the 20th century, but in the meantime another issue was making itself felt. The porous chalk soil that it had passed through had always caused leakage problems on the Wendover Arm – in particular the length from Tringford to Drayton Beauchamp – and it was getting worse. At times it had leaked so badly that far from acting as a feeder, it was actually taking water away from the main line. Various methods of lining it were proposed and some of them tried, but after a period
during which this length was drained, dammed off, and the canal had to rely largely on the Wilstone reservoirs (which were fed from beyond the far end of the leaky section), a report in 1910 led to more drastic measures being taken.
The Arm was closed to navigation, the water level of most of it was lowered (to below the level of some of the leaks), and the Tringford to Drayton length was drained. A pipeline was laid (mostly buried in the drained canal bed), to connect supplies coming down the Arm to the Tringford reservoir and to the pumping station where a third well-shaft (confusingly now referred to as No 1) was dug and a third pump added (and 30 years later in 1944, a further pump in a separate building, to pump water directly from the pipeline into the Arm next to the pumping station). Meanwhile the old steam pumps, which had done the job reliably for 100 years but were inherently hungry on fuel, were replaced by electric ones, initially supplied by on-site diesel generators.
And that’s more-or-less how things have run since then. But in recent years two issues have arisen: firstly those pumps have been showing their age. And secondly thanks to the efforts of the Wendover Arm Trust, the dry length of the Arm is gradually being given a waterproof lining and will in due course (along with the remainder of the Arm to Wendover) be restored to navigation.
Matters reached a serious state in recent times, leading to the current project to secure this vital part of the southern GU’s water supply system for the future. The pump in the No 2 well (which can supply the canal from any of the reservoirs) hasn’t been operable since around 2007. For the pump-spotters among you it’s a Rees Roturbo from 1911 powered by a City Electrical motor, and sadly it was regarded as beyond repair. More recently the No 3 well pumps (also capable of drawing on any of the reservoirs), another pair of slightly younger (1927) Rees Roturbo pumps but powered by motors from Lancashire Dynamo, also failed – and at present a temporary pump is replacing them. And finally, the No 1 pump (which can only pump from Tringford Reservoir), a Sykes with Compton Parkinson motor dating from a replacement in 1960, is currently out of service and under refurbishment.
At the same time the pipeline under the dry bed has been taken out of service owing to leaks: in due course it will no longer be needed, as once the Wendover Arm is reopened the water can flow straight through to the Main Line like it originally did. But that’s a little way off, and in the meantime the old heading which once linked the former Whitehouses pump to Wilstone Reservoir it being put back in service to continue its function. This is a good example of the 19th century meeting the 21st, as a state of-the -art ROV (Remotely Operated Vehicle – Charles describes it as basically “an underwater drone”) was sent up the heading under remote control to check its condition, and it’s now in use.
The major part of the project has been to replace the No 2 pump. Two new pumps have been sourced, and are currently being installed such that one can be kept on standby and easily switched over for servicing, in case of a fault, and to provide a longer lifespan before the next refurbishment or replacement is needed. They will fulfil the main pumping requirement. At the same
time, the No 3 pumps have been taken out and will be preserved within the building as non-functioning historic artefacts – and that’s a reminder that the building’s a listed structure, with a lot of historic features dating from its steam, diesel and electric eras - although it’s also seen many changes, such as the removal of the upper storey of the building when it was no longer needed to house the beams of the steam engines.
Finally, one historic artefact which will remain in use once refurbished is the No 1 pump from 1960, which will continue to provide supplementary capacity pumping from Tringford Reservoir.
So next time you’re cruising past on the Grand Union, take a detour along the Wendover Arm to Tringford. Just before the terminus (you can now turn a fulllength boat there, thanks to WAT’s restoration progress), look out for a brick building half-hidden by vegetation on your right, near an old stop-lock. That’s the pumping station, built for beam-engines in the early 19th century, and still the heart of a pumping scheme where modern equipment is working with 200-year-old reservoirs, culverts and wells to (hopefully) keep the Grand Union from running dry.
The electric pumps in Tringford No 3 Well, dating from 1927
...and during the rebuilding after conversion to electric power
...and as it was when it still housed steam powered beam-engines...
The Tringford pumping station building today...
The oldest electric pump dating from 1911 is removed from pump well No 2
Beyond repair: a shaft from one of the No 3 pumps
Looking down into the No 2 pump well: the shower of sparks is from removal of steelwork from the old pump
Makers’ plate from the motor of one of the No 3 pumps
1940s plan of the reservoirs and connections. Report and plans have been useful for the current work
Plans from a 1940s report for the Grand Union company: details of Tringford