How to unblock a soil pipe

Waste Soil Pipe

Most properties have one or more, but to many people, a soil pipe is just one of a network of pipes that run through our homes and businesses. However, like all pipes and parts of our plumbing systems, they play an important role in keeping our buildings clean, safe and running smoothly, so it’s certainly beneficial to be knowledgeable about what they are and what they do.

What is a soil pipe?

Soil pipes remove all waste from baths, sinks, and toilets. The waste is transported to an allocated drain, but the system works in tandem with vents in the roof of the building to ensure there are no unwanted fumes.

The water that leaves the aforementioned parts of a building is known as greywater or blackwater. This water flows into a wastewater pipe, which allows all the gases to escape upwardly, while gravity ensures the water ends up in your septic tank or the sewer that your drains are connected to.

Also known as…

They can also be known as the stench pipe, soil stack, drain waste vent systems.

How do I know if I have a blocked soil pipe?

With normal household pipes, like the ones under your sink or the ones that run through your home, you can tell if they’re blocked because water will drain slowly and you may experience lower water pressure. With soil vent pipes, you will also notice a slow-draining toilet, as well as some unpleasant odours emanating from the drains.

How do I fix a blocked soil pipe?

Your soil pipe is either going to be located above your roof, or on the side of your property. The older pipes, the ones that are made of cast iron, are the ones that tend to protrude from the roof. More modern, plastic ones are often located on the side of the building, branching out in a tree-like shape.

Before we start, it’s important to note that the top of the gas vent can be become blocked by leaves and other debris. Where possible, ensure the cover is intact or any blockages are cleared, and you might be able to avoid the following unblocking process altogether.

DIY Steps

Fixing a blocked soil pipe requires a bit of bravery if you’re going to do it yourself, as the blockage can be quite unpleasant.

  1. The first thing to do is ensure you are properly equipped – protective clothing and a face mask are a must, so don’t start the task of unblocking until you’re appropriately attired.
  2. You may hit a stumbling block right away if your pipe is made of cast iron. The heavy-duty nature of this pipe means that it will be cleared using a vent above the roof, which will be difficult and possibly dangerous to access without the help of a professional engineer.
  3. If your pipe is a plastic one, as most modern ones are, then you are able to proceed with the DIY unblocking.
  4. The next step is to locate the ‘cleaning eye’. This is a large hinge that is found where the branch pipes join the main stack. Once you’ve found this, you can unscrew it and insert a drain auger – this can also be called a ‘snake tool’, ‘toilet jack’ or even an ‘electric eel’. This tool is used in any plumbing situation when a plunger can’t or won’t work.
  5. Pass the auger through the pipe until you reach the blockage. Once located, simply crank the handle – this releases a coiled wire. You can then push and pull the auger and the wire will hopefully remove the blockage, allowing any backed-up water to start flowing freely again.
  6. Once you’re sure it’s clear and the water is flowing, be sure to disinfect the stack thoroughly, using anti-bacterial spray and a hose, before putting it back together.


Express Drainage Solutions are the leading providers of drain installation, maintenance and repair for customers throughout London. From unblocking to the location of cracked pipes and leaks, we do it all, and we do it promptly and professionally, too. For more information about our work, please feel free to get in touch with us today.

Want more information?Contact us today on 020 3124 1785

EDS unblocked and repaired over 20,000 drains last year for the residents and businesses of London.

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