Surface Water Flooding West Sussex | Check Drains Now

The Environment Agency issued a Flood Alert for parts of West Sussex on 26 August 2026. Up to 40mm of rain overnight, covering the Elbridge, Lidsey, Aldingbourne, Barnham, Yapton and Ryebank Rifes catchments. Surface water flooding expected. Residents warned to act.

That's the coastal fringe, I know. Not Roffey, not Broadbridge Heath, not Southwater. But here's the thing most people miss: when the EA issues an alert like that, it's not telling you the problem started with the river. It's telling you the drains gave up first.

Surface Water Doesn't Wait for a Watercourse

I've been pulling blocked gullies out of front drives across RH12 and RH13 for years. Every time we get a proper August downpour, my phone starts going. Not because the River Arun has burst its banks. Because someone's gully pot hasn't been touched in three years and is packed solid with silt, leaves, and whatever fell off the tree above it.

Here's how it actually works. Rain hits a hard surface, say a driveway on a Trafalgar estate terrace, or a car park at a small business in Broadbridge Heath. It needs somewhere to go, fast. If the gully pot is clear, water drops into it, passes through the lateral drain, and eventually finds its way into a surface water sewer or a soakaway. Takes maybe 30 seconds.

If the gully pot is blocked, that 30-second journey becomes a flood. The water backs up. It spreads. It finds the lowest point, which is usually your front door threshold or a neighbour's fence panel. At that point you're not dealing with a drainage problem anymore. You're dealing with insurance forms.

The Barnham and Yapton area caught it on 26 August because those catchments sit low and the rifes can't shift water fast enough when the sky drops 40mm in a few hours. But the same physics applies everywhere in West Sussex. The only difference is how quickly private drainage fails before the public sewer even gets involved.

What 40mm Actually Means

40mm of rain sounds abstract. Put it this way: a 40mm event over a standard semi-detached roof in Littlehaven dumps around 2,400 litres of water into your drainage system in a few hours. A single gully pot, even a clean one, has a capacity of roughly 30 to 45 litres. The downpipe, the gully, the lateral drain, they're all working flat out.

Now add a gully pot that's half-full of silt, which is most of them after a dry summer. Suddenly your effective capacity is 10 litres, maybe less. That 2,400 litres of roof runoff has nowhere to go quickly.

And it's not just residential. I had a job last month at a small industrial unit near Horsham town centre. They'd had surface water backing up under the roller door every time it rained hard. The cause? A single gully pot in the forecourt, completely silted up. Took us 20 minutes to clear with high-pressure jetting. The damage to the stock inside had taken weeks to sort out.

Could've been avoided for the cost of one gully clearance a year.

The Three Things to Check Before Autumn

I'm not going to pretend this is complicated. Most drainage problems that cause surface water flooding on private land come down to neglect, not bad luck.

Gully pots. Lift the grating if you can do it safely. If you can see silt, debris, or standing water that isn't draining, it needs clearing. High-pressure water jetting shifts it properly. Poking it with a stick just moves the problem further down the pipe.

Rodding eyes and inspection chambers. Open them. Look in. If there's a waterline stained well up the sides, or worse, debris sitting in there, your drain is already telling you it's struggling. These are access points engineers use to clear blockages and run CCTV cameras. If yours are buried under decking or paved over, that's a problem I see constantly on newer estates in Holbrook and North Heath.

Downpipes and connections. Walk around your property after rain. Are the downpipes actually connected to a drain at the bottom, or is water just soaking into the ground by the wall? A surprising number of properties I visit in Warnham and Slinfold have downpipes that were disconnected from drains at some point and never properly reconnected. When it rains hard, all that water goes straight against your foundations.

Why a CCTV Survey Is Worth It Before October

If your gullies are visibly clear and your inspection chambers look fine, that's a decent start. But it tells you nothing about what's happening inside the lateral drain itself.

Roots are the big one. We run CCTV drain surveys across Horsham and the surrounding villages all year, and the number of pipes in RH12 and RH13 with root intrusion from garden trees, ash, willow, oak, is genuinely staggering. A partial root blockage might drain fine in dry weather. Add 40mm of overnight rain and the same pipe backs up completely.

Cracked or displaced pipe joints are another one. Clay drain pipes, which are common in older parts of Roffey, Denne, and Forest, shift over decades. A small displacement causes silt to collect at the joint. It's not noticeable day to day. Under storm load, it becomes a blockage.

A CCTV survey shows you exactly what's there before it becomes an emergency. It takes a couple of hours. You get footage. You get a clear explanation of what we found and what, if anything, needs doing. Some of the drains we survey are perfectly fine. We tell people that too.

Remedial work we carry out, drain repairs, relining, pipe replacement, comes with a 20-year guarantee. That's not small print; it's how we stand behind the work.

The Honest Opinion

The flood alert that hit West Sussex on 26 August isn't a freak event. It's a preview. August storms, September deluges, November saturation. We get them every year. The drainage that fails spectacularly in October is the drainage that was already compromised in August.

The EA alert was for Barnham and Yapton. The next one might cover ground closer to home. The homeowners and landlords in Cowfold, Partridge Green, Pulborough, Billingshurst, and the Horsham estates who get ahead of this now are the ones who won't be calling me in a panic at 10pm on a wet Tuesday in November.

Drainsco covers Horsham and the RH postcodes, with engineers available 24 hours a day, seven days a week. There's no call-out fee, and we give you a clear price before we start. If you want gullies cleared, a CCTV survey booked, or just a conversation about what you're looking at, give us a call.