A drain that copes fine in dry weather but overflows every time it rains hard is giving you useful information. Heavy rain exposes weaknesses that normal use does not, so an overflow is often a symptom rather than the problem itself.
Common reasons drains overflow in heavy rain
- Blocked gullies and grates. Leaves, silt and debris stop surface water reaching the drain, so it pools and spills over instead.
- Too much water at once. Roofs, patios and driveways can send a large volume of rainwater into one drain in a short time, more than the pipe can carry away.
- Ground water getting into the pipe. Cracked or displaced joints let water seep in from the surrounding soil, which adds to the flow and can overload the system.
- A full or failing soakaway. If rainwater is meant to drain into a soakaway and the ground around it is saturated or silted up, the water has nowhere to go.
- Pressure on the wider sewer network. In some areas public sewers struggle during storms, which can cause water to back up into private drains.
Whose problem is it?
If the overflow is coming from pipework within your boundary, it is usually yours to sort out. If it is a public sewer under the road or a shared lateral, it may be the water company’s responsibility. Our guide on who to call for a blocked drain explains how to tell the difference.
What to do when it happens
- Keep people and pets away from any water that may contain sewage
- Do not use water inside the property more than you need to until levels drop
- Take photos and notes of when and where it happens, as this helps diagnosis
- Get the drain checked once the weather settles, rather than waiting for the next storm
A CCTV drain survey shows whether the pipe is cracked, displaced or silted up, and whether groundwater is entering it. After serious flooding, our guide on post-flood CCTV drain surveys covers what to check.
If your drains overflow whenever it rains, it is worth finding out why before the next storm. Call us on 0333 200 1623 or use our contact page and we will help.