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All you need to know drainage gullies

Drainage gullies by definition is a drainage fitting with an open top, a definite base and outlet with one or more sides. Gullies can be used to connect wastewater outlets or stormwater/rainwater outlets to suitable drains, depending on the type. Drainage gullies can also be used to prevent drain blockages, as they let the wastewater drain, preventing any rodents or bad smelling gasses from escaping.

Varieties of drainage gullies explained…

Here at PolyDrainage we provide 3 main types of gullies. We have P Trap gullies, Bottle gullies and Road Drainage gullies.

Drainage Road gully gratings

Bottle gullies come with a grid already attached, which matched the trap. However, if you have a road drainage gully you will require a separate grating. Our gully gratings are made from composite or ductile iron and are accessed via being hinged down or being able to be completely removable. 

Our gratings are into categories based on their load class. We have load classes A-F with each class referring to a different intended traffic level and weight. 

Below shows a breakdown of the grating load classes:

  • Load Class A15 (1.5 tonnes) – Perfect for any lightly trafficked areas including, cycle and pedestrian pathways, greened areas, school yards and other landscaped areas. 
  • Load Class B125 (12.5 tonnes) – This load class can handle slow moving traffic e.g., car parks, pathways, garage drives and courtyards.
  • Load Class C250 (25 tonnes) – This load class is suitable for any roadside drainage, slip roads and petrol stations.
  • Load Class D400 (40 tonnes) – This is typically used for highway areas, such as, carriageways motorways, and pedestrian roads.
  • Load Class E600 (60 tonnes) – E600 is used mostly in commercial areas such as roads in industrial areas, non-public roads, and other areas where high wheel loads may occur. 
  • Load Class F900 (90 tonnes) – F900 load classes would be used in airports , military bases, and any other special surfaces.

To put the load classes into perspective the average patio drainage fitting can use anything from load class A15 upwards, however a carriageway (road) needs to be a minimum load class of D400. 

Road drainage gullies – 

Road gullies are much larger than your bottle gully, however, the work in pretty much the same way. Our road gullies are made from plastic, creating a lightweight easy to use units. They act as liners for concreate castings, when all the correct pipework has been successfully connected. The concrete is used to provide extra strength and resist deformation.  

Road gullies are used to handle much heavier traffic in areas such as motorways, airports they are made with a trap that collects the sediment and stops any odours from getting out. Road gullies are used to hold rainwater, they are connected to the main drainage system, which will be discharged into a near by waterway. Road Gullies usually come with grids on top and an found along the side of most of the roads.

Gully Outlet | Polydrainage.co.uk

P trap gullies – 

P Trap gullies have been named for the P shaped bend in the centre , the reasoning behind this is brought to trap the water that flows into the gully. The water flows through the gully hopper and then enters a central chamber, connecting to the main drainage system. Having the bend in the middle of the system creates a barrier, stopping any gasses a foul smells getting out into the air. 

You can purchase P Trap bottle gullies in both 90° and 45°, they both function in similar ways. P Trap gullies usually come with a socket and rubber seal to allow you  to connect a pipe into it. However, sometimes they may arrive with out the need for a coupling to connect the gully to the drainpipe. 

The main difference between P Trap gullies and bottle gullies is that P Trap gullies are not roddable. 

PolyDrainage - 110mm Underground Low Back P Trap Gully

Bottle Gullies – 

The principle of bottle trap gullies are very similar to P Trap gullies. However, bottle gullies also known as compact, universal or yard gullies are distinctive for being roadable. This also means the central chambers within the trap are removable, making it much easier when you need to clean the gully, or remove any blockages. 

This is the more suited gully to homeowners as it is much easier to maintain, you can simply remove the trap, was it and replace it. 

Bottle gullies can come with either a fixed unit or with an adjustable top, which makes it easy for you to adjust the grid to the ground height. Plain ended gullies have one outlet to connect the gully to the sewage system. Back inlet gullies are designed to have an inlet on the back, allowing you to attach this to another drainage run. 

110mm Back Inlet Bottle Gully

Maintaining your gullies… 

To prevent any blockages in your gullies you need to keep up with the maintenance. It is suggested that you do so with seasonal checks, especially after a rainy or windy weather. Clearing out your gullies regularly is the key to ensuring your gullies last and an no unwanted smells arrive the gully will last as long as possible. 

However, if you are faced with a blockage, the method of removal is totally dependent on the type of gully installed. It is much easier to remove any blockages from a bottle gully due to the system being roddable and having a removable trap with an easy outlet pipe for access. To remove the blockage all you need to do is remove the chamber an insert your drainage rod this will allow you to dislodge the blockage. 

A P Trap gully on the other hand is a much harder unblocking. You will need to use a drainage specialist as they are more than likely going to use electronic mechanical pipe cleaning. 

PolyDrainage - 160mm Bottle Gully