You might have heard the name before — but what is a gully drain? Gully drains are drainage fittings that are designed to remove surface water or divert waste water. These drains are a key aspect of any drainage system, helping to prevent waterlogging around properties and roads.
There is a selection of types of gully drain — P Trap gullies, bottle trap gullies, and road gullies. In this article, we’re offering our expert insight on each variation of gully drain, and the best ways to maintain them.
What is a Gully Drain?
A gully drain is fitted to discharge surface water. They connect to the nearest suitable drain outlet to divert the excess water away, such as a wastewater pipe or a storm drain.
So, what is a gully drain able to do? When surface water builds up, after heavy rainfall or flooding, it is channelled through a grid (the external drain cover that you can see on the surface). This helps to catch debris like leaves and litter before it enters the water system, which can minimise the risk of blockages. The water then enters the gully system underground.
Different types of gully drain are made in various styles, as we will explain in the next section, but the basic universal premise is that the gully drain collects water in a small reservoir called a gully trap, below an opening to the pipe that carries surplus water away. As surface water enters the gully, the level of water in this reservoir rises until it reaches the exit point of the water flow pipe, allowing the excess to be piped out of the system and away from the road or property. By constantly holding a small reserve of water in the reservoir due to the depth difference of the pipes, the gully drain creates an airtight seal that prevents sewer gases from escaping.
Types of Gully Drains
P Trap Gully
A P Trap gully is often found underneath a drainpipe on the outside of a building. The grid beneath the drainpipe helps to prevent debris from entering the system. A P Trap gully is shaped like a horizontal letter P, allowing water to accumulate in the curve of the pipe (called the water trap). As the water level rises, it fills another section of pipe called the gully pot. Once the gully pot is full, the water flows away from the property.
Bottle Trap Gully
Also used in domestic settings, a bottle trap gully functions in the same way as a P Trap gully — it is typically used in areas with limited space, because it relies on depth rather than horizontal breadth. Although they both use a surface grid and are found under drain pipes, a bottle trap gully differs from a P Trap gully in that it features a deeper vertical chamber that serves as the gully pot. This simple chamber is fitted with a pipe outlet about halfway up the pot to allow accumulated water to flow away. Bottle trap gullies are also much easier to clear with drain rods if they do happen to accumulate some debris, such as leaf matter.
Road Gullies
Designed to keep highways clear of surface water, road gullies are the final example of the types of gully drains. They demonstrate heavy-duty drainage features, giving them the ability to cope with very high levels of run-off. They are often made of concrete and are fitted with heavy-duty grating to withstand the volume and weight of traffic. They run parallel to the road and feed any excess water into storm drains designed to cope with high volumes, which keeps the surface clear of flooding and allow vehicles to pass safely.
Where are Gully Drains Found?
Whether in a domestic or road setting, gully drains are usually placed strategically to manage surface water runoff. In homes and commercial properties, they are often found in driveways and around buildings — the purpose of the domestic gully drain is to keep the property safe from damage or obstruction due to excess water. A road drainage gully, however, is often found in the centre of the road, running parallel to the flow of traffic.
Domestic vs. Road Gullies — Key Differences
There are several key differences between domestic and road drain gullies. Road gully features are designed to withstand traffic and cover a large area, meaning that they are typically much larger and stronger than the gullies that you will find in a domestic setting. Domestic drainage features are focused more on using space efficiently and protecting the foundations of the surrounding buildings, leading to smaller systems with higher run-off.
How to Maintain a Gully Drain
Regularly performing gully drain maintenance can limit the risk of clogs and ensure that the system keeps running smoothly. Here are our TWC tips and tricks on how to maintain a gully!
- You will need a pair of sturdy gloves, a garden hose, and a drain rod.
- To prepare for your drain gully maintenance, ensure that you are taking appropriate safety precautions — consider wearing eyewear, and always ensure that you are using thick gloves to protect your hands from debris.
- To locate the gully, find where your drain pipe meets the ground, which will flow directly into the gully grid. Check this area for leaves and litter, making sure that any debris is removed from the grid to prevent it entering the water system.
- Remove the gully cover carefully — the metal grid is likely to be heavy. Set it aside safely for later.
- You can check your gully drain for blockages by using your garden hose to fill the gully trap with water. If the excess water drains away and the water level returns to normal, your system is functioning normally. If the water continues to rise and then does not drain away, you may have a partial or complete blockage.
- Using drain rods may have differing levels of success depending on the type of drain gully that your property uses. A bottle trap gully is easier to clear than a P Trap gully due to its shape. Carefully insert the drain rod until you feel resistance, and then gently push forwards and twist to help with clearing the blocked gully. If the clog does not shift, please do not attempt to use excessive force, as this can damage your pipes — call TWC, and we will solve the issue using professional equipment!
- To remove a mild clog or loose debris, you can rinse the gully using your garden hose, particularly on the jet setting. However, if you notice the water backing up and refusing to drain, turn off the hose immediately and call a professional. If you have a stubborn blockage and continue to introduce water to the system, you could inadvertently flood the gully.
- Once you are satisfied that the clog has cleared, you can test the water flow by once again using your garden hose to fill your gully trap. If the water drains back to its original level, simply reseal the gully cover securely, and make a note to check the gully again in around a month for visible debris.
Preventing Blockages in Gully Drains
As we often say here at TWC, drain blocking prevention is better than cure! Our gully maintenance tips are simple and easy, allowing you to prevent gully blockages as much as possible.
- Regularly inspect your drain gullies. Walk around your property and ensure that there is no debris building up near the drain grids (if you find any, remove it immediately), and never pour any dirt or grease down your drains, as this can cause the gully to clog.
- If your gullies are in an area that is prone to debris, such as below a tree that sheds its leaves, use a drain cover for further protection from blockages.
- Schedule professional inspections at least one a year. The TWC team will be happy to help you maintain your drain gullies and protect your property. Using the latest technology, we can inspect the entire underground system with CCTV drain surveillance cameras and remove any blockages or debris with professional grade drain rods and high-pressure jetting. We can also provide specific expert advice for the ongoing care for your drainage system.
Gully Drain Issues and When to Call a Professional
Despite their largely self-sufficient design, like all drainage systems, sometimes gully drains require professional help. Due to their challenging shape and vital purpose, if you notice any worrying symptoms in or around your gullies, contact the professionals. At TWC, our friendly and experienced team offer industry-leading drain repair services to help solve the issue and keep your property protected.
How do you know when to call a drain expert? Some key signs of gully drain issues that you should look out for include slow drainage, a build up of water around the drain grid, foul odours, and persistent blockages. These all indicate problems below ground, which we can inspect and diagnose using our CCTV drain survey equipment.
Benefits of Regular Gully Maintenance
By following our adivce, you can help to keep your gully drains functioning at their best. Gully drains are truly the unsung heroes of your drainage system — they protect you from back-flowing sewer gases, avoid water damage to property foundations, and support efficient drainage throughout your land. A properly functioning gully also helps to support the environment by reducing surface water pollution. To avoid potentially costly repairs (or your lawn turning into a lake overnight!), it is well worth investing some time in gully drain maintenance.
If you do need support with your gully drains, TWC are here to help. We never charge a call-out fee, all our work is fully guaranteed, and we are industry leaders across the North East, Yorkshire and Lincolnshire. Contact us today, and we will be happy to assist you.
