How To Stop An Office Chair From Sinking

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Do you ever get that sinking feeling? You’re not alone. This can happen after a few years, as your office chairs have been in constant use. The ‘sinking’ feeling is a common occurrence in office chairs, due to the pneumatic valve used to adjust the seating platform.

This can be easily rectified, by understanding just how your office chair works.

What does pneumatic mean?

Pneumatics  – and hydraulics – are used in heavy pieces of machinery. Pneumatic systems use compressed air to enable movement. The machinery needs constant supplies of compressed air, which is provided by an air compressor.

The compressor works by sucking in air and storing it in a high-pressure tank (a receiver). This compressed air is then moved through a series of pipes and valves to enable power – and movement – to the machinery. Hydraulics uses the same system, but with oil. A pneumatic system is, therefore, lighter, cleaner – and cheaper.

Pneumatics in office chairs 

Office chairs are pretty clever things! Instead of heavy manual ways of changing the seating arrangements of your chair, the pneumatic element of modern office chairs allows them to be easily adjusted. A pneumatic office chair has a single-acting cylinder. This is a spring that has been filled with air. When the piston is moved further out of the chamber, the air inside the chamber expands, allowing the seat to lower. If your chair keeps sinking, this means that the cylinder is no longer working.

How to stop an office chair from sinking

Is the sinking fixable? Absolutely. But before you attempt to clean the cylinder it’s worth making sure that the other parts that assist the mechanism are in good working order. Ensure that the lever is well oiled. Then start on the cylinder itself; there are two ways of doing this…

The PVC Pipe method

  1. You will first need to slide the plastic tube away from the extendable cylinder so that it is possible to see the metal cylinder beneath. Measure this cylinder for its width, length and circumference.
  2. Buy a PVC pipe that is the same length. The diameter of the replacement pipe should be exactly the same or a bit larger.
  3. Using a small hacksaw, cut the new pipe from one opening to the other side, so that you can then slide it onto the cylinder. If you like, you can even remove the chair’s wheelbase and slide on the new PVC pipe without the need for cutting!

Your chair should now stop sinking! You may need to adjust the length of the pipe when adjusting the height of the chair.

The hose clamp method

  1. As with the previous method, slide the plastic tube from the existing cylinder, to enable you to see the metal cylinder underneath.
  2. Clean the metal cylinder thoroughly.
  3. Decide on the chosen height of the chair (this cannot be adjusted later).
  4. Wrap a few layers of duct tape or scuff the cylinder with sandpaper to give your hose clamp extra grip.
  5. Wrap a 2cm hose clamp around the circumference of the cylinder. Then loosen the screw on the hose clamp and pull the belt end out. Wrap the clamp around the metal cylinder, tighten then slide to the top of the cylinder.

Your chair should stop sinking! Only use this method if you know the exact desired height of the chair.

You may need to replace the pneumatic cylinder. If this is the case, check with the chair’s manufacturer details first.

Don’t want to fix your office chair?

It may be time to invest in a new office chair. Don’t know what to choose? Browse our huge selection of office chairs – from leather executive office chairs and mesh chairs to comfortable ergonomic chairs such as this ergonomic draughtsman chair, there’s something for everyone at Manutan.




Victoria Vaughan