The siphon gully top is a manhole installed below the drainage grates and used to collect rainwater. Their main application is in sewers and non-pressurised underground drains outside buildings (code U application area).
In this type of manhole, the presence of the siphon is fundamental as it allows the water coming from the road surface to be dispersed, preventing it from causing unpleasant odours and unhealthy exhalations, and preventing obstructive material from entering the pipe.
The gully tops can be made of plastic: Polieco’s rectangular gulley top, for example, is made of black powder medium density polyethylene (density no less than 0.930Kg/dm3). This type of product is chosen for its low weight as it facilitates laying operations and also ensures high water tightness.
Polyethylene siphon gully tops are produced by a rotational moulding process and have an outlet for the connection of plastic pipes (PEAD or PVC).
The plastic gully top can also be made with flame-retardant features if they are laid in tunnels. To achieve this variant it is necessary to use self-extinguishing material with a flammability rating of V2 according to UL94, suitable for the rotational moulding production technique.