Choosing the Right Flexible Shaft for Vertical Stacks

If you’ve spent any time in the drain cleaning industry, you’ve probably faced that all-too-familiar situation: you’re using a flexible shaft to clear a vertical stack, and suddenly a resident rushes out in a panic to tell you their apartment is flooding.

To help you avoid this kind of scenario, let’s take a closer look at how to use flexible shafts in vertical stack applications—and how to handle the job more safely and efficiently.

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Why Flexible Shaft Thickness Is Important

When working inside a vertical stack, shaft rigidity is key. And the general rule of thumb is simple: thicker shafts provide more control. The added stiffness helps the shaft stay on course and prevents it from coiling or jamming as it climbs.

Thinner shafts, such as 6 mm or 8 mm, can cause significant problems when used in vertical stacks. Their high flexibility often leads them to spiral or coil inside the pipe, making it difficult—or even impossible—to push them further.

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Use 10 mm or 12 mm for Better Results

For vertical stack cleaning, we recommend starting with a 10 mm flexible shaft or going up to 12 mm for added stability. These thicker shafts are more suitable for vertical applications, especially over longer distances.

That said, thicker shafts are also heavier, which brings its own set of challenges—particularly when working from the bottom up.

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Top-Down Is Best

Whenever possible, position yourself at the top of the stack and feed the shaft downward. This method takes advantage of gravity and significantly improves control. Trying to push a heavy, stiff shaft upward for several floors not only wastes energy but also increases the risk of losing your grip on the tool.

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How Long Can a Shaft Go?

Based on customer feedback, the longest successful vertical shaft run we’ve heard of reached 200 feet (around 60 meters). In that case, the technician used a 12mm flexible shaft and constructed a hoist at the top of the stack to manage the tool and prevent it from slipping.

While 200 feet isn’t typical, it demonstrates what’s possible with proper planning, the right equipment, and safe handling practices.

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Conclusion

Vertical stacks pose unique challenges, but with the right flexible shaft and technique, they can be handled efficiently and safely.

Make sure to select the appropriate shaft size, work with gravity when you can, and plan ahead for long runs. These small decisions can save time, prevent property damage, and keep your operations smooth.

Check out the video we made on this topic for a closer look at the process in action.