The first design of the Kennet & Avon canal by the distinguished Scottish civil engineer, John Rennie, called for a 4.5 km (2.5 mile) tunnel between the Wiltshire villages of Crofton and Burbage but, in those days, tunnelling was a very expensive and uncertain process and a cheaper alternative was sought. This involved raising the summit level of the canal and constructing a much shorter tunnel. However, this new summit was 12 m (40 ft) higher than any reliable local, natural water source and so a pumping station was needed at Crofton to keep it topped-
Crofton Pumping Station was built in 1807 and started work soon after. The first engine installed in the building was a 0.9 m (36 inch) bore Boulton and Watt which had a wooden beam and began working in 1809. In 1812, a 1.06 m (42 inch) bore Boulton and Watt engine was installed beside it. In 1846, the 0.9 m bore Boulton and Watt was replaced by a Sims Combined Cylinders Engine constructed by Harvey of Hayle.
The pumping station is located 1¼ km (¾ mile) to the east of the summit. It raises the water to a level slightly above that of the summit, delivering it via a specially constructed feeder channel, called, from Cornish tin mine practice, a leat.
Both the 1812 Boulton and Watt, and the 1846 Harvey engine (in its final form) are in working condition, and are steamed publicly on several weekends through the summer months from a coal fired Lancashire boiler. When the Pumping Station is in steam, it actually carries out the job for which it was built as the electrically powered pumps, that now normally do the job, are switched off.
Although not part of the original station, there are a number of interesting small stationary steam engines in the boiler house, which are also run when the station is in steam.