How to Tell If Your Drainage Gullies Are Blocked And How to Clear Them

You might notice that your drainage gullies have become blocked if the area around them is flooding, unpleasant smells have arisen or if there is more serious damage within your drainage system. These are some of the early warning signs you can be vigilant for, with debris building up beneath the grate an additional indicator of an issue.

In many cases, you can clear minor blockages yourself with some gloves, hot water and a bucket to collect up the leaves, silt and grease. But persistent drainage issues may point to further issues.

This month at Express Drainage Surveys, we’ll explain exactly how to tell if your drainage gullies are blocked, how you can go about unblocking minor obstructions, and when it’s time to seek out professional assistance. As experts in CCTV drainage surveys, we know a thing or two about getting to the bottom of drainage issues.

What is a drainage gully and what does it do?

Your drainage gully is an external drain designed to collect surface water and sometimes run-off from wastewater pipes. This then directs the water to the main underground drainage system. Here is where you’re likely to find gullies:

Situated beneath the roof gutter downpipes
Alongside your patio or driveway
Close to a kitchen or utility room waste outlet

To help trap water and prevent foul sewer gases from rising back up out of the gully, most will feature a built-in trap, which works a lot like a sink U-bend.

The role of a gully is pretty simple: to handle surface water and prevent flooding by channelling it safely away from your home. If your gullies become blocked, both rainwater and foul water won’t be able to drain efficiently, creating the risk of damp and structural issues.

Common signs that your drainage gully is blocked

Learning to spot the early signs of a blocked drainage gully can help you stay ahead of more serious problems. Here are five things to look for:

Standing water around the gully: This is one of the clearest and most obvious signs. Water pooling around the drain cover itself, after rainfall, can mean there’s an issue, especially if it lingers for hours or days.
Downpipes are slow to drain: If your roof downpipes are overflowing and you notice water spilling from your guttering, it’s a sign of a blocked gully. When it rains, these should be flowing freely, so it’s time to take action if not!
Bad smells outside your property: Do you get hit with unpleasant odours when you step out the door? It could mean a blocked gully. Gullies shouldn’t emit strong odours, but organic matter decomposing will definitely stand out.
Visible debris build-up: You will probably be able to see how full the gully is through the grate, but you can always lift it up and check to see if it has become packed with leaves, moss, silt, mud and congealed grease.
An overflowing gully in heavy rainfall: Next time there is a downpour, look at the gully grate. If it’s overflowing immediately, it suggests a severely restricted flow, overwhelming your drain easily.

What causes drainage gullies to become blocked?

Now you know the signs, it’s time to look at the potential culprits of a blocked gully:

Leaves and garden debris: One of the most common in autumn is leaves that have washed and blown into your gully. This can quickly build into a compact sludge.
Moss from roof tiles: In high winds or heavy rain, moss can be washed down the downpipe, gradually forming a blockage in the trap.
Silt and soil: Naturally, when surface water washes into the system, so does a certain amount of silt and soil, especially with a nearby garden bed or lawn.
Fat, oil and grease: If connected to the kitchen wastewater, a certain amount of fats and oils poured down sinks can start to solidify in the gully once in the cooler air outside.
Tree roots: If you’ve cleared the gully consistently but still find it gets overwhelmed, it could be that tree roots have penetrated the pipework further along, creating a restriction to the flow of water.
Damaged or collapsed pipework: Similarly, any portion of the pipework further along that is simply damaged or has collapsed can prevent proper drainage, causing your gully to overflow.

How to clear a blocked drainage gully safely

As mentioned in the opening of this piece, minor blockages can be cleared safely with a little care and a few basic pieces of equipment:

Step 1: Ensure you have the proper safety measures in place. This includes heavy-duty, waterproof gloves and eye protection. You should avoid direct contact with wastewater, as well as chemical cleaning products.
Step 2: Remove the grate and clear surface debris that you can see. This will mean lifting up the metal or plastic grate, potentially with the help of a screwdriver. You can then remove leaves and other sludge by hand or using a small scoop.
Step 3: Next, you should clean the removable water trap or bucket insert. This will get rid of any accumulated sludge within the gully to help provide as much capacity and flow as possible.
Step 4: Flush the system with hot water (not boiling) to dissolve any grease and wash away smaller particles.
Step 5: Replace the trap and the grate. You can then pour water down the drain to see if it flows. If things have improved, then it was likely just a minor blockage.

If these steps don’t resolve the issue, it means you will likely need the assistance of professionals to uncover the cause and location of the blockage further in the system.

CCTV drainage surveys from the professionals

When a blockage can’t be resolved with surface-level cleaning, our CCTV drainage survey can provide a clear, accurate diagnosis. At Express Drainage Surveys, we use the latest camera technology to inspect your drain and record video evidence as part of our report.

You can learn more about this and our other drainage services using the links below:

Remember: ignoring issues with your drainage gully could be a sign of deeper problems, so contact us today to book an appointment.