Every distillery will have at least two condensers, one for each still, and most have more (depending on the number of stills). What makes them less obvious is that they come in two very different forms, and are often either slightly separate from the better known parts of the process (sometimes outside the buildings altogether), or overshadowed by the copper glory of the stills.
Condensers come either as tubes or worms. The worm condenser comprises a coil of copper tubing immersed in a large (usually, but not always) circular tank of water, usually raised above ground level. A good example of this is at Dalwhinnie Distillery, where the large worms, often mistaken for water tanks, sit outside the front of the distillery. The vapours enter at the top and the condensed liquid emerges at the bottom. At Cragganmore Distillery the water tanks housing the worms are square in shape and found at the rear of the distillery. At Oban Distillery the worm condensers are housed in the roof of the distillery.
The tube condenser brings the idea up to date, and is more efficient than the worm. It operates like a reversal of the processes inside a steam engine. The condenser is tubular in form and made of copper. It stands on one end and contains a series of copper tubes through which cold water is piped. Again, the vapours enter at the top of the condenser, and the liquid flows out of the bottom. (Continues below image...)
At Glenmorangie the tube condensers are placed close to the walls of the still room and attract little attention from the passing groups of visitors inevitably more fixated on the stills themselves. At other distilleries the condensers are placed outside: while at Bowmore one of two spirit condensers is inside the still room and the other one in the yard outside.
A unique exception to the general rule can be found at Dalmore Distillery, where each spirit still has a condensing jacket around the still top. It is arguable that this is actually part of the distillation process rather than truly part of the condensation process, but reference is included here out of interest.
But whatever their form, their role is to provide rapid cooling for the vapours coming from the stills. Being made of copper they also act to prolong the complex chemical reactions already taking place within the still, and as such also play their part in adding to the flavour of the finished product.
A wash condenser, or a condenser attached to a wash still, coverts the vapours back to liquid low wines that are then piped to the low wines receiver en route to the spirit still. A spirit condenser converts the vapours from the spirit still into a liquid that is then directed to the spirit safe for analysis.
And if you want to see a condenser at its most basic, take a look at the illegal home distilling kit on display at the Museum of Islay Life Here you can see the origins of the worm condenser, where what emerges from the still is led directly through a coil of pipe in a wooden bucket of water. The condensers in use at Dalwhinnie and Cragganmore are rather larger, but their function is identical.