A trapped gully is a surface water or waste gully that incorporates a built-in water seal trap to prevent drain odours and insects from rising into the open. UK Building Regulations Part H1 generally require gullies receiving foul discharge from waste pipes to be trapped, with a minimum seal depth of 50mm. Trapped gullies are typically installed at the discharge point of kitchen and washing machine wastes on the outside wall of a property, where flows pass over a grating and through the trap before joining the drain. Older glazed stoneware versions are common at the rear of Victorian London terraces and can fracture over time. Regular cleaning is needed to keep the grating clear of leaves and the trap chamber free of grease and food residues.
Trapped gully
Gully fitted with a water seal trap to prevent drain odours rising to the surface.
