Causes of sewer flooding
The common causes of sewer flooding include blocked drains, heavy rain, groundwater infiltration and damaged pipes.
Blocked drains
Blocked drains and sewers are often the cause of sewer flooding. We deal with thousands of blockages on our network every year.
When a sewer gets blocked, sewage cannot pass through the pipe as it usually would. This can then cause sewage to back up into homes.
Heavy rain
Our sewers are designed to take sewage away from properties. Some sewers also take away surface water. This is run off from roads, footpaths and paved areas.
They can deal with day-to-day flows, but very wet weather can overwhelm them. This can then cause sewer flooding.
Groundwater infiltration
Sometimes groundwater gets into drains and sewers. This is called groundwater infiltration. It usually happens during or after heavy rain.
Most homes connect to a public sewer through private drains. These carry foul water from baths, washing machines and toilets.
When groundwater is high, it can get into public sewers and private drains. It enters through small cracks in pipes or inspection chambers. Over time, this can overwhelm sewers and cause flooding.
Damaged pipes
Many of our sewers were built at the start of the last century or earlier. Because the pipes are underground, it’s not always obvious when they are damaged.
Tree roots or soil movement during very dry or winter weather can damage them. This makes sewer flooding more likely.