What Is a Drain Gully and What Are They Used For?

Drain gullies, sometimes known as gully traps, are ground-level drains designed to discharge water from your property or a road surface. This can include surface water from highways and roads, rainwater from your gutters, grey waste from your kitchen or bathroom such as your washing machine, dishwasher, baths, and showers.

Drain gullies typically fit into two categories, road gullies and domestic gullies. A drainage gully’s primary purpose is to connect waste and stormwater with the mainline drain. They also stop bad smells and rodents escaping from the drain as well as helping to stop blockages by preventing leaves and twigs from entering.

Where Is a Drain Gully Found?

A domestic drain gully exists outside of your property, typically at a discharge point where a grey waste discharge pipe or rainwater downpipe from your roof meets the ground.

A road gully is typically found at the side of a road or highway, but it can also be found in places where surface water flooding is common, such as car parks and airports.

Drain gullies usually have a grate or grid placed over the opening to avoid external debris such as leaves and twigs from collecting and blocking the pipework and water flow.

If the drain gully overflows or is slow to drain there may be a blockage, you must promptly clear the blockage to avoid flooding damage to your property or rising odours from smelly drains.

What Types of Drain Gullies Are There?

There are two types of domestic gully traps commonly used; a P Trap Gully and a Bottle Gully. They do the same job but work slightly differently due to their shape.

P Trap Gully

P trap gullies, get their name from the shape which commonly looks like a U-bend or the letter P, work by trapping water in the curve section. This acts as a barrier to seal off raising smells from the drainage below.

A P trap gully is the most common type of gully drain, but this does not mean it comes without its difficulties, as it can easily become blocked and cannot be cleared by rodding due to its shape.  A drainage specialist can provide alternative methods of drain unblocking to resolve the issue and break down any debris making it easier to remove.

Outdoor Gully Trap

Bottle Gully

The bottle gully design helps remove the common problem of blockages found in P trap gullies as there is no tight bend in the pipe to trap water. Bottle gullies make use of an inner sleeve that acts like a bottle. Water drops into the middle of the bottle trap and is then forced up between the sleeve and the side to an outlet pipe that connects with the main drainage system. The bottle gully design still uses water to trap rising smells and gasses.

An advantage of the bottle gully is that it uses a removable sleeve, making cleaning a more straightforward task. As such, bottle gullies are a newer style gully drain and are used more commonly on newer properties and pipework.

Road gullies are much larger than domestic gullies. They work in a similar way and can typically drain an area of up to 250m2. They are placed at the road or kerb edge and covered from the top with a metal grate or grid.

How to Correctly Maintain a Drain Gully

Every drain gully in a property must be routinely maintained to avoid the risk of flooding and blockages.

You can do this by simply inspecting your grates for debris or slow flowing water, making sure your drain gully isn’t blocked with leaves, twigs or other debris clogging the flow of water.

Don’t underestimate how important drain gullies are to the performance of your properties drainage system and how important it is to maintain them regularly. Should a blockage occur, a specialist drainage engineer will be able to use equipment that breaks down the blockage into smaller pieces, allowing it to be removed or flushed through the drainage system. Do not be tempted to do this without the correct tools or skills required to safely clean a drain gully, as you will risk pushing the blockage further into the drainage system or displace the pipe, potentially making the problem worse.

If you need help with a drain gully, Metro Rod are available 24/7 to resolve any blockages and repairs. Contact your local depot.