Drains Flooding Heavy Rain Tewkesbury | Why It Happens

If you're standing in your garden watching water rise around the gully, or you've come downstairs to find the ground-floor toilet gurgling like something's trying to escape, you're not imagining it. Tewkesbury drains back up in heavy rain for very specific, fixable reasons. Some of them are down to the town's geography and infrastructure, which you can't change. Some are down to your own pipes, which you can. Here's how to tell the difference.

Why Tewkesbury is Different to Almost Everywhere Else

Most towns sit on reasonably well-drained ground. Tewkesbury doesn't. It sits on a flood plain at the confluence of the Severn and the Avon, with the water table already high for much of the year. When heavy rain arrives, the ground is often already saturated before a single drop hits your drain. Water has nowhere to go quickly.

Add to that the age and design of the drainage network. Much of the older part of town, and several of the established estates, runs on a combined sewer system. That means surface water from your roof and driveway travels down the same pipe as foul water from your toilets and sinks. Under normal conditions, that works. Under sustained downpours, the combined sewer gets overwhelmed. When it does, the path of least resistance is back up through the lowest point in the system. In most houses, that lowest point is your ground-floor toilet or a yard gully.

Newer areas, parts of Northway, Wheatpieces, and Walton Cardiff built in the last twenty years, tend to have separated systems. Surface water goes to a soakaway or a watercourse; foul goes to the sewer. These properties fare better in storms, though not perfectly.

The Three Things That Are Actually Happening

When your drain backs up in heavy rain, one (or more) of three things is going on.

1. The public sewer is overwhelmed. Severn Trent's infrastructure takes the combined flow from thousands of properties. In a prolonged downpour over GL20, the sheer volume of surface water entering the combined sewer can exceed the pipe's capacity. Sewage has to go somewhere, so it surcharges, meaning it rises under pressure inside the network. Your private drain connects to that network. If the pressure is high enough, it comes back towards you. You'll often notice this affecting several neighbours at once.

2. Your lateral drain or private sewer is partially blocked. Even a small build-up of grease, roots, or debris inside your own drain can be irrelevant on a dry day when flows are low. Add a heavy rain event and you're suddenly trying to push a lot of water through a narrowed pipe quickly. The blockage that was invisible on Tuesday becomes a full surcharge on Thursday evening when the storm hits. This is the one you can actually do something about.

3. Your surface water connection is overwhelmed or misconnected. In some older properties around Newtown, Priors Park, and Mitton, surface water drainage was simply connected to the nearest available drain decades ago, which was often the foul drain. That 'misconnection' is now illegal, but many still exist. Every time it rains hard, your foul drain is taking on surface water it was never designed to carry.

Low-Lying Spots That See This Most

Some parts of the area flood faster than others and it's worth being honest about which ones they are.

• Mythe Road and The Mythe flood from both the Severn and through drainage back-pressure. Gullies there can be underwater before the main flood event even peaks.
• Bredon Road and Southwick Park sit low relative to the Avon catchment and surcharge regularly after sustained rain.
• Priors Park has a mix of drainage ages and some combined sewer runs that were never upgraded.
• Twyning and Bredon village are outside Tewkesbury town but within the GL20 area we cover, and both sit in the Avon flood plain. Drainage there relies heavily on watercourse outfalls that back up when the river level rises.
• Ashchurch has newer separated drainage on the residential roads, but the industrial areas near Ashchurch Road have older infrastructure that struggles in heavy events.
• Bishop's Cleeve, just south on the B4632, is slightly higher ground but has its own clay-heavy soil that doesn't drain surface water quickly, pushing more volume into road gullies than they're designed for.

None of this means these places are doomed to flood every time it rains. It means the margin for error in those drains is smaller. A partial blockage that a property in Winchcombe might never notice becomes a real problem in a house on Bredon Road.

What You Can Actually Control

You can't control the water table. You can't redesign Severn Trent's sewer network. You can control the condition of your own drainage, and that matters more than most people realise.

Keep your private drain clear

Your responsibility runs from your property to where your drain connects to the public sewer. That lateral drain, and any shared sewer serving multiple properties before it reaches the public network, is yours to maintain. A CCTV drain survey will show you exactly what's in there. Root ingress from garden trees is extremely common in Tewkesbury's older streets. Grease and fat build-up is near-universal in kitchen drains. Neither shows symptoms until the system is stressed.

Check your gullies

Yard gullies and driveway gullies are the first thing to block with leaf debris, silt, and general garden waste. Lift the cover. If the trap is full of sediment, that gully is already working at reduced capacity. In a storm, it stops working entirely. Clearing a gully takes ten minutes and costs nothing.

Think about your downpipes

If your rainwater downpipes connect to the foul drain (common in properties built before the 1970s in parts of Newtown and Mitton), you're adding a significant volume of surface water to a pipe that wasn't designed for it. A drainage engineer can check this with a dye test in under an hour. Separating a misconnected downpipe to a soakaway or water butt is a practical fix that reduces your flood risk.

Don't pave over your front garden

This one's a slow-burn problem. Properties across Northway and Walton Cardiff that have replaced front gardens with block paving or concrete are sending water directly to the road drain rather than letting it soak into the ground. Multiply that across a street and the gully at the end of the road is overwhelmed in minutes. Permeable paving is the planning-compliant alternative if you want a hard surface.

Don't wait for an emergency to get a survey

If your drains back up every single time it rains heavily, that's a pattern. A one-off might be a network surcharge you had no control over. Two or three times a year means something in your pipes is making the situation worse. A CCTV survey after the event can show you exactly where the restriction is, whether it's a root ball, a collapsed section, a bellied pipe holding water, or silt accumulation. Knowing that changes the conversation from "why does this keep happening" to "here's what we fix".

When It's Severn Trent's Problem, Not Yours

If you've checked your gullies, your drain's been surveyed and is clear, and you're still backing up in heavy rain, it's quite likely the cause is sewer surcharging in the public network. You can report this to Severn Trent on 0800 783 4444. They have a legal duty to investigate and, if the public sewer is causing flooding to your property, to address it. Keep records: dates, photographs, what backed up and when. You'll need them.

Severn Trent's surface water management work in the GL20 area has been ongoing for several years. Some streets have been upgraded; others are still waiting. Knowing whether your street is on combined or separated drainage gives you useful information when you're having that conversation with them.

After the Flood: What to Check First

Once the water recedes, a few quick checks tell you a lot.

• Look at the manhole in your garden or driveway. If there's a tide-mark of sewage above the normal invert level, the system surcharged. That's a drainage event, not just surface flooding.
• If the backup came through your ground-floor toilet or bath, the issue was almost certainly below-ground pressure rather than a simple blockage.
• If only one drain in the property backed up, it's more likely to be a localised blockage in a branch pipe than a network-wide surcharge.
• Smell matters. Surface water backup smells of rain and mud. Foul sewer backup smells unmistakably of sewage. The two events have different causes and different fixes.

If there's any doubt about whether contaminated water has entered the property, treat affected surfaces as you would any sewage spillage: full disinfection before anyone walks through. Don't let children or pets near it until it's clean.

The Honest Summary

Tewkesbury's flood risk is real, structural, and not going away. But the difference between a property that handles heavy rain and one that backs up every winter is often the condition of the pipes under the garden. The geography is fixed. The drains aren't.

Drainsco covers Tewkesbury and the surrounding GL postcodes. Engineers are available 24 hours a day, seven days a week, and there's no call-out fee. If your drains are backing up in rain and you want to know whether it's your pipes or the network, give us a ring. We'll give you a clear price before we start anything, and if it turns out to be Severn Trent's problem, we'll tell you that honestly too.