If you’ve found yourself searching for how to unblock external drain, you’re probably staring at a pool of murky water outside your home wondering what went wrong. Blocked external drains are one of those annoying household problems that seem small at first until they start to smell, overflow, or cause flooding.
The good news is that many outside drain blockages can be sorted without calling an engineer straight away. In this guide, we’ll walk you through why external drains get blocked, how to unblock an external drain step by step, and when it’s best to bring in a professional.
Why Do External Drains Get Blocked in the First Place?
External drains (sometimes called outside drains or inspection chambers) connect your home’s wastewater to the main sewer system. Over time, it doesn’t take much for them to clog up.
One of the most common causes is garden debris. Leaves, mud, moss, and small twigs get washed into the drain, especially during heavy rainfall or autumn months. Once that debris settles, it starts trapping more waste, eventually restricting water flow.
Another big culprit is grease and fat from the kitchen. Even though you rinse it down the sink inside your house, it cools and solidifies in the pipework. Over time, it builds up and creates stubborn blockages.
Then there are wet wipes and sanitary products. Despite what the packaging may claim, most “flushable” wipes don’t properly break down. They combine with grease and debris to form solid obstructions deeper in the drain.
In some cases, the issue is more serious. Tree roots can grow into cracked or ageing pipework, restricting flow and catching waste. If this happens, DIY solutions may only offer temporary relief.
Signs Your External Drain Is Blocked
Before you start lifting covers, look out for the tell-tale signs:
Water pooling around the drain cover
Slow drainage after rainfall
Gurgling sounds from pipes
Unpleasant smells outside
Overflowing water during heavy rain
If you notice one or more of these, it’s likely you’re dealing with a blockage.
Step-by-Step
How to Unblock External Drain: Step-by-Step
If you’re specifically looking for a clear, practical breakdown of how to unblock external drain, here’s a straightforward step-by-step guide you can follow.
Step 1: Gather Your Equipment
Before you start, make sure you have:
Thick rubber gloves
Old clothes
Screwdriver or drain lifting key
Drain rods
Bucket of hot (not boiling) water
Hose (optional)
Safety comes first drain water can contain bacteria, so avoid direct contact wherever possible.
Step 2: Remove the Drain Cover
Carefully lift the external drain cover using a screwdriver or drain key.
If it’s stuck, gently lever it up don’t force it too aggressively.
Once open, inspect inside:
Is the chamber full of water?
Can you see visible debris?
Is the water slowly draining or completely still?
This helps you understand how severe the blockage is.
Step 3: Remove Surface Debris
If you can see leaves, sludge, mud, or solid waste near the top:
Manually remove it using gloves
Use a small shovel if necessary
Place waste in a bin (never back into another drain)
In many cases, clearing visible debris immediately improves flow.
Step 4: Check the Water Level
After removing debris:
Wait a few minutes
See if the water level begins to drop
If it drains away, the blockage was likely near the surface.
If it remains high, the obstruction is deeper in the pipe.
Step 5: Insert Drain Rods
If the blockage is further down:
Assemble your drain rods
Insert them into the pipe opening
Push gently while rotating clockwise
Always rotate clockwise to avoid unscrewing the rods inside the pipe. When you feel resistance, you’ve likely reached the blockage.
Step 6: Break Up the Blockage
Once you’ve located it:
Continue twisting the rods
Push and pull gently
Work through the obstruction until resistance reduces
Be patient forcing the rods can damage pipework, especially in older properties.
Step 7: Flush the Drain
After clearing the blockage:
Pour a bucket of hot (not boiling) water down the drain
orUse a garden hose to test the flow
If the water drains freely and quickly, you’ve successfully unblocked it.
Step 8: Replace the Drain Cover
Once you’re confident the blockage is gone:
Securely replace the drain cover
Clean the surrounding area
Safely dispose of any waste
What If It Doesn’t Work?
If you’ve followed the steps and water still isn’t draining properly, the blockage may be further down the line or caused by something more serious.
Chemical drain unblockers are available, but they should be used carefully and strictly according to instructions. Avoid mixing products, and don’t rely on chemicals if tree roots or structural damage are suspected.
Persistent blockages often require professional equipment such as high-pressure water jetting or CCTV drain inspections to properly diagnose the problem.
When Is It Best to Call a Professional?
While learning how to unblock external drain yourself can save money, there are situations where calling a professional is the smarter option.
If the drain keeps blocking repeatedly, multiple drains are backing up, or water is coming back into your home, it’s time to get expert help. These signs may indicate a deeper issue in the main sewer line.
Tree root intrusion, collapsed pipes, or large-scale grease build-up won’t be fully resolved with DIY tools. In fact, repeated attempts to clear a stubborn blockage can sometimes cause more damage.
A professional drainage engineer has the tools and experience to identify the exact cause and fix it properly the first time.
Preventing Future Blockages
Once your drain is flowing again, a little maintenance goes a long way.
Installing a drain guard can help stop leaves and debris from entering. Avoid pouring fat, oil, or grease down the sink, and never flush wipes or sanitary products. Regularly checking your external drains especially after heavy storms can prevent small build-ups from becoming major blockages.
Final Thoughts
Knowing how to unblock external drain is useful for any homeowner. Many minor blockages can be resolved with basic tools and a bit of patience. However, if the problem keeps coming back or seems more serious than a simple debris build-up, professional help is often the safest and most cost-effective solution.
If you’re dealing with a stubborn outside drain blockage and want it sorted quickly and properly, getting an experienced drainage specialist involved can save you time, stress, and potentially costly repairs down the line.
Don’t let a blocked external drain turn into a bigger problem early action makes all the difference.
Need Help With a Blocked External Drain?
Our experienced drainage engineers use professional equipment including high-pressure water jetting and CCTV drain inspections to locate and clear the problem quickly and safely.
Don’t wait for overflowing water or costly damage.
Contact us today for fast, reliable external drain unblocking and get your drainage system flowing properly again.