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How to clear blocked pipes?

How to clear blocked pipes?

Posted on 13 January, 2023

In order to understand how to clear blocked pipes, it’s important to first understand what a waste pipe and a waste trap are. 

What is a waste pipe? 

A waste pipe is an integral part of your drainage system at home, as they take away wastewater from your home and transport it to a sewage system. Waste pipes let wastewater flow from your sinks, shower, bath, washing machine, or dishwasher.

Your waste outlet pipes are larger in diameter than your supply pipes, for instance, a hand basin has a 32mm waste outlet pipe. Whereas a shower, washing machine, or sink has a 40mm pipe. 

When a waste pipe is installed, it’s a requirement that it slopes down by 20mm every metre, this ensures that the wastewater is transported freely. Originally, waste pipes used to be made from lead, but now they’re made from high-quality plastic. 

What is a waste trap?

Waste traps on the other hand are also a vital part of the drainage system at home, as they stop drainage smells originating from sinks or toilets from coming back into the home through a seal. 

Anything that’s plumbed in and discharges water into a drainage system is either fitted with a waste trap or has one incorporated into its design. Waste traps are quite simple in design, and are just a u-shaped loop of pipe that is located below a waste outlet.

Common waste trap designs are the P-Trap which has a horizontal outlet, and there’s also the S-trap which has a vertical outlet.

Now that you understand what a waste pipe and trap are, let’s see how you can unblock a sink and toilet. 

What you’ll need

For this guide, you’ll need basic household products:

  • A sink and toilet plunger
  • Chemical drain cleaner
  • A bucket
  • Drain auger (May not be required but good to have just in case)
  • Protective gloves and eyewear

How to clear a blocked sink

If your sink, basin, or bath is slower than usual to drain, chances are the waste pipe is blocked. The typical causes of slow draining are grease being stuck in the waste trap, or fibres underneath the plug. 

If the water doesn’t drain away at all though, there’s a complete blockage in the waste pipe, which means there’s an obstruction somewhere. Here are 4 tips for unblocking the waste pipe:

  1. Partially fill the sink with water, then place a sink plunger over the plug-hole. Pump up and down with the plunger, and repeat a couple of times. Take your plunger away to see if the water drains.
  2. If the water doesn’t drain, put on your gloves and eyewear and pour some chemical drain cleaner down the plug-hole. Ensure you do not mix it with chemicals such as bleach as this creates hazardous gasses.
  3. If the above steps fail, go below the sink and place a bucket under the waste trap and remove the waste trap to empty its contents into the bucket. Once empty, screw the waste trap back in and see if the water drains.
  4. If you still have no luck, then unscrew the waste trap again and probe into it using a drain auger. 

How to clear a blocked toilet

The signs of a blocked toilet are when the water in the pan rises to the top of the toilet and proceeds to drain very slowly. 

Here are 4 tips for clearing pan outlet blockages:

  1. Pour a bucket of warm water into the pan and see if this clears the pan outlet.
  2. If not, use a toilet plunger in the pan outlet and pump up and down. Repeat multiple times.
  3. If this still hasn’t cleared the pan outlet blockage, use a drain auger designed for a toilet. Use protective gloves and insert the auger into the outlet to try and clear the blockage. 
  4. If the issue still persists, there could be an issue with the main drainage line. 
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