Understand The Components Of Your Residential Drainage System

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Every property has a drainage system. It collects the wastewater from your property and deposits it in the main sewer, allowing it to be taken to the water treatment plant and processed, eventually returning to your home as drinking water.

Your drainage system doesn’t just cover the wastewater from your toilet, sinks, and shower. It also covers the rainwater that falls on your property and the ground around your home.

All of this water needs to be directed away from your property to help complete the water cycle and prevent your home from flooding.

Most of the time the system works perfectly. But, if it starts to back up or flow slowly, you’re going to need a good drain camera and to understand the various components of your system.

Interior Pipework

Inside your home, you will have various water appliances, such as a sink, toilet, washing machine, and even a dishwasher. All of these items use water and then send it down the drains. Most of the appliances use 40mm pipes although some will use 32mm.


Under every appliance will be a trap. This can be a ‘P’, ‘S’, or a ‘U’ shape. The purpose of these traps is to capture water and hold it, effectively blocking the pipe. Every time you send water down the drains it moves the existing water and replaces it. The purpose of this water is to stop air passing through, effectively protecting your home from gases produced by the waste in your pipes.

The traps are the most likely part of the pipes to block, followed by any corners.

All these pipes join together at the main waste pipe, usually a 100mm pipe.

Outside Your Home

The 100mm waste pipe will drop down inside or outside your home and then travel across your yard to reach the main sewer, which is usually situated under the road.

It is your responsibility up to the main sewer. There should be several inspection hatches in your yard, allowing you to check the progression of the wastewater and deal with any blockages.


Alongside this, there will be gutters on your roofline. These are connected to downpipes, bringing the water off your roof and down to surface level. This water will then need to be directed away from your home. This is usually done by sloping the ground to encourage the water to go to your drainage system.

There are several types:

  • Ditch

It is possible to simply have a ditch running alongside your land and all rainwater is directed to it. The ditch allows the water to be soaked safely into the land and carries excess away.

  • French Drain

A French drain is similar to a ditch in that it is a hole in the ground. The hole will be filled with gravel and, at the base of the hole will be a collection of pipes, allowing the water to filter into the ground and disappear into the soil at the root level. This is very beneficial to the plants and surprisingly effective.

  • Main Sewer Pipe

In some cases the downpipes are connected to the main sewer drains, increasing the flow through the drains and helping to keep sewage moving.