Just west of Ardrishaig is an ingenious solution to the area's
water control problem. A unique device located on the canal bank
between Lock 4 and Oakfield Bridge, the Auto Waster was built
in 1885 by John Groves to regulate the level of the pound between
Ardrishaig and Cairnbaan.
The system consists of two large buckets suspended on a 'rocker'
arm. There is a channel cut through the canal bank into the
building and as soon as the water level rises, the water floods the
first bucket making it heavy. This in turn pulls down on the
rocker and raises the second bucket which is rather like a huge
bath plug in the canal bank.
Once lifted, the water cascades under the road and safely out to
the sea, 9.8m (32ft) below. As the canal level falls the water flow
into the Waster also reduces. The first bucket has a small hole to
allow it to empty, so as it becomes lighter, the second bucket
is lowered and seals the canal again.
Simple and effective - it has to be! When in full flood, the
water flow can reach some 197 tonnes per minute!