What the 2026 wet season exposed about drainage in Mid Sussex

The Wet Season Didn’t Cause the Problems — It Exposed Them

One of the biggest things we’ve noticed is that the rain didn’t create new problems out of nowhere.

It simply exposed what was already there.

We’ve attended properties where:

• Drains had been partially blocked for months
• Pipes had small cracks allowing root ingress
• Systems had been altered or extended incorrectly
• Older pipework was already near failure

In dry conditions, these systems might continue to “just about work”. But once the ground becomes saturated and water flow increases, those same systems start to struggle very quickly.

Poor Renovations and Cut Corners Are Showing Up

Another major trend this year has been issues linked to recent building work or renovations.

We’ve come across:

• Incorrect pipe falls causing poor flow
• Connections made into the wrong lines
• Gullies installed without proper discharge
• Soakaways that simply cannot cope
• Pipework buried without proper bedding or protection

In many cases, everything looks fine on the surface. But underground, the system isn’t set up properly.

Again, in normal weather this might not be obvious. But with the amount of rain we’ve had, these weak points are being exposed.

Hydraulic Overload in Hassocks and Hurstpierpoint

In areas like Hassocks and Hurstpierpoint, we’ve seen a noticeable increase in what we refer to as hydraulic overload.

This is where the public sewer system becomes overwhelmed during heavy rainfall. Instead of water flowing away from properties, it begins to back up or slow down dramatically.

The results can include:

• Overflowing gullies
• Backflow from sewer lines
• Flooding in low points such as garages and cellars
• Silt and debris being pushed back into private drainage

We’ve attended multiple properties where the system simply could not discharge fast enough because the main sewer was already under pressure.

Signs That Something Is Being Looked At

From what we’re seeing on the ground, it appears that work is beginning to be carried out to address some of these issues.

There are signs that efforts are being made to:

• Separate surface water and foul water systems
• Reduce the load on combined sewers
• Improve overall drainage infrastructure

This is a positive step, but these changes take time. In the meantime, properties connected to older or shared systems can still experience problems during heavy rainfall.

Flooded Cellars and Saturated Ground

Another issue this year has been ground saturation.

In many parts of Mid Sussex, especially areas with clay soil, the ground simply cannot absorb any more water after prolonged rainfall.

This leads to:

• Water sitting around foundations
• Cellars and basements taking on water
• Surface water entering drainage systems that are already under strain

When both the ground and the sewer system are overloaded at the same time, problems escalate quickly.

Sewer Smells Becoming More Common

We’ve also seen a sharp increase in reports of bad smells inside homes.

These are often linked to:

• Overloaded sewer systems pushing gases back
• Partial blockages holding stagnant waste
• Dry traps in less-used areas being affected by pressure changes
• Build-up of fats and debris breaking down in pipes

Again, these issues are not always new. The wet conditions simply make them more noticeable and more frequent.

Secondary Blockages Caused by Overload

One of the less obvious effects of hydraulic overload is the creation of secondary blockages.

When sewer systems are under pressure:

• Flow slows down
• Debris settles more easily
• Silt and solids can be pushed back into private drains

This creates new restrictions within the system, which can then turn into full blockages even after the rain has passed.

What This Means for Homeowners

The key takeaway from this year is simple:

If your drains are showing signs of struggle, there is usually a reason.

Common early signs include:

• Slow draining sinks or showers
• Gurgling noises
• Outside drains backing up in heavy rain
• Persistent smells
• Water appearing where it shouldn’t

These are often warning signs that the system is under stress.

Understanding the Sussex Context

The combination of clay soil, hilly terrain, and mixed-age housing stock across Mid Sussex creates unique drainage challenges.

In Burgess Hill, older interceptors and clay pipework are still common. In Haywards Heath, newer developments often tie into existing combined sewers. Meanwhile, in Hassocks and Hurstpierpoint, runoff from nearby fields and high water tables can push surface systems to their limits.

That’s why we always take a tailored approach. Installing an NRV is not a one-size-fits-all fix — it’s about assessing where the risk lies, whether that’s in the property layout, elevation, or sewer position.

Dealing With Issues Early Makes a Big Difference

This year’s wet season has been a reminder that drainage systems are often out of sight, but they play a critical role in how a property functions.

When everything is working properly, you don’t think about it. But when conditions change, the system is put to the test.

Across Hassocks, Hurstpierpoint, Haywards Heath, Burgess Hill and Mid Sussex, we’ve seen just how quickly problems can appear when that system is pushed beyond its limits.

Frequently Asked Questions

Why do drains struggle more during heavy rain?

Heavy rainfall increases the volume of water entering the drainage system. If pipes are partially blocked, damaged, or connected to overloaded sewers, they may not be able to cope, leading to slow flow or flooding.

What is hydraulic overload in drainage systems?

Hydraulic overload happens when the public sewer system becomes overwhelmed during heavy rain. This can cause water to slow down, back up, or even return towards properties instead of flowing away.

Why am I getting sewer smells in my house after rain?

Wet conditions can push sewer gases back through pipes, especially if the system is under pressure or partially blocked. Build-up in the pipes can also start to break down and create strong odours.

Can heavy rain cause blocked drains?

Yes. Rain can wash debris into drains, slow down flow in already restricted pipes, and expose existing issues like root intrusion or collapsed pipework.

Why are cellars and low areas flooding more often?

Ground saturation means water cannot soak away properly. Combined with overloaded drainage systems, this can lead to water building up and entering low areas such as basements and garages.

What should I do if my drains overflow during rain?

Stop using water where possible and contact a drainage specialist. Overflowing drains may indicate a blockage, pipe damage, or pressure from the main sewer system.