The Worm Tub: An Old-School Method, but Not a Vanished Art

February 22, 2024 –––––– Danny Brandon, , , ,

The name might sound off-putting, but the worm tub is a traditional part of the whisky making process. In earlier times, this old-school condensing method was used by distillers far and wide, but advances in technology have made it far less prevalent than it once was. And yet, surprisingly, a number of distillers remain loyal to the worm tub.

What Is a Worm Tub?

Worm tubs are an old type of condenser. They consist of long and winding copper piping—called “worms” because of their snakelike appearance—housed inside a giant wooden tub filled with cold water. As the wash comes to a boil in the distilling process, its vaporized liquid rises up the neck of the still and into the lyne arm, the long pipe at the top of the still. From there the vapor runs through winding pipes submerged in a cold water tub, a process that cools it into liquid before it goes into the spirit safe. Regular condensers turn that process inside out: the vapor instead travels from the lyne arm to a vacuous copper chamber with running tubes chilled by running water. The vapor cools when it comes into contact with the surface of these pipes, liquifying and trickling down the side of the chamber into a safe.

When Rosebank Distillery restarted production last year, it replaced its old wooden worm tubs with new ones made from steel.

Why Are Worm Tubs Less Popular Today?

Worm tubs were widely used for generations, but ultimately fell out of favor due to the difficulty of maintaining and operating them. The copper pipes are prone to leaking, and the leaks are difficult to detect and often discovered too late. Once a leak is identified, repairs are another headache. The winding and bending nature of the worms makes replacing them difficult and costly.

Also, the tubs can hold tens of thousands of liters of water, and their sheer size makes the cleaning process very labor-intensive. The cost associated with keeping them constantly pumped with water is another consideration. By the 1960s, most distillers had replaced worm tubs with the smaller, more efficient shell and tube condenser. Nowadays worm tubs are thus a rare sighting in the whisky landscape. But some whisky makers still swear by the method.

Speyburn's two spirit stills are hooked up to a traditional worm tub (pictured). The distillery's wash still, however, uses a shell and tube condenser.

Do Worm Tubs Impact a Whisky’s Taste?

Condensers play an active role in affecting the character of a whisky, and different methods will produce very different liquids. The reason lies in the degree of interaction between the vapors and the copper pipes. On average, worm tubs condense vapors far more quickly than shell and tube setups, which leads to less copper interaction, resulting in a whisky that feels “thicker” or “heavier”—creating a heft and a full-bodied quality that these distillers say can’t be matched by other condensers. Suntory’s flagship distillery, Yamazaki, is noted for having stills of all shapes and sizes, and that goes for the condensers too. But the wash stills have worm tubs, for the same reason that other distillers like them—to produce heaviness in the distillate.

But devotees of worm tubs have different reasons for continuing to use them. Some, like Kanosuke Distillery, say it’s about familiarity. The Kagoshima, Japan-based whisky distillery was founded in 2018, but its nearby Hioki Distillery had already been making shochu using worm tubs for over a century. Shun Nakamura, Kanosuke’s head of distillery and chief blender, says the decision to tub condense the whisky was directly informed by their shochu-making techniques.

For the Scots, it’s more a question of adhering to a long and storied tradition. In the Highlands, Wick-based Old Pulteney Distillery uses equipment that mirrors the designs used by earlier generations of whisky makers. “It’s very similar to the original kit that would’ve been used in the early 20th century,” said distillery manager Malcolm Waring. “To this day we still use the original design of our worm tubs, which very few distillers do.”

The recently reopened Lowlands-based Rosebank Distillery has found a way to modernize its design while still holding to tradition. When the distillery relaunched, instead of shifting to shell and tube condensers, it opted to replace its wooden tubs with ones made from stainless steel clad with larch wood. “It allows us to use the same tools as have been historically used at Rosebank,” says distillery manager Malcolm Rennie. “Our aim is to try and make a spirit with all the classic Rosebank characteristics, so reinstalling worm tubs will allow us to closely recreate that signature style.”

Distilleries like Speyburn have taken an altogether different approach. The Speyside distiller’s wash still is set up to work with both worm tubs and shell and tube condensers. Distillery manager Euan Henderson says, “[worm tubs] result in a more full-bodied, flavorsome and sulfur-y new make spirit. When combined with shell and tube condensers, it can also bring out a fruitiness which we look for in our new make spirit.” The Japanese Yamazaki Distillery also operates on a similar dual-condenser system.